| Message ID | 20220426114627.2.I4ac7f55aa446699f8c200a23c10463256f6f439f@changeid |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [1/2] drm/probe-helper: Add helper for drm_helper_probe_single_connector_modes() | expand |
Missed one more comment. On 4/26/2022 12:16 PM, Abhinav Kumar wrote: > Hi Doug > > One minor comment below. > > But otherwise, looking at this change this should work for us acc to me. > > We will test this out with our equipment and then provide R-b. > > Thanks > > Abhinav > On 4/26/2022 11:46 AM, Douglas Anderson wrote: >> As per Displayport spec section 5.2.1.2 ("Video Timing Format") says >> that all detachable sinks shall support 640x480 @60Hz as a fail safe >> mode. >> >> A DP compliance test expected us to utilize the above fact when all >> modes it presented to the DP source were not achievable. It presented >> only modes that would be achievable with more lanes and/or higher >> speeds than we had available and expected that when we couldn't do >> that then we'd fall back to 640x480 even though it didn't advertise >> this size. >> >> In order to pass the compliance test (and also support any users who >> might fall into a similar situation with their display), we need to >> add 640x480 into the list of modes. However, we don't want to add >> 640x480 all the time. Despite the fact that the DP spec says all sinks >> _shall support_ 640x480, they're not guaranteed to support it >> _well_. Continuing to read the spec you can see that the display is >> not required to really treat 640x480 equal to all the other modes. It >> doesn't need to scale or anything--just display the pixels somehow for >> failsafe purposes. It should also be noted that it's not hard to find >> a display hooked up via DisplayPort that _doesn't_ support 640x480 at >> all. The HP ZR30w screen I'm sitting in front of has a native DP port >> and doesn't work at 640x480. I also plugged in a tiny 800x480 HDMI >> display via a DP to HDMI adapter and that screen definitely doesn't >> support 640x480. >> >> As a compromise solution, let's only add the 640x480 mode if: >> * We're on DP. >> * All other modes have been pruned. >> >> This acknowledges that 640x480 might not be the best mode to use but, >> since sinks are _supposed_ to support it, we will at least fall back >> to it if there's nothing else. >> >> Note that we _don't_ add higher resolution modes like 1024x768 in this >> case. We only add those modes for a failed EDID read where we have no >> idea what's going on. In the case where we've pruned all modes then >> instead we only want 640x480 which is the only defined "Fail Safe" >> resolution. >> >> This patch originated in response to Kuogee Hsieh's patch [1]. >> >> [1] >> https://lore.kernel.org/r/1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com >> >> >> Signed-off-by: Douglas Anderson <dianders@chromium.org> >> --- >> >> drivers/gpu/drm/drm_probe_helper.c | 26 +++++++++++++++++++++----- >> 1 file changed, 21 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/gpu/drm/drm_probe_helper.c >> b/drivers/gpu/drm/drm_probe_helper.c >> index 819225629010..90cd46cbfec1 100644 >> --- a/drivers/gpu/drm/drm_probe_helper.c >> +++ b/drivers/gpu/drm/drm_probe_helper.c >> @@ -476,7 +476,6 @@ int drm_helper_probe_single_connector_modes(struct >> drm_connector *connector, >> const struct drm_connector_helper_funcs *connector_funcs = >> connector->helper_private; >> int count = 0, ret; >> - bool verbose_prune = true; >> enum drm_connector_status old_status; >> struct drm_modeset_acquire_ctx ctx; >> @@ -556,8 +555,8 @@ int drm_helper_probe_single_connector_modes(struct >> drm_connector *connector, >> DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n", >> connector->base.id, connector->name); >> drm_connector_update_edid_property(connector, NULL); >> - verbose_prune = false; >> - goto prune; >> + drm_mode_prune_invalid(dev, &connector->modes, false); >> + goto exit; >> } >> count = (*connector_funcs->get_modes)(connector); >> @@ -580,9 +579,26 @@ int >> drm_helper_probe_single_connector_modes(struct drm_connector *connector, >> } >> } >> -prune: >> - drm_mode_prune_invalid(dev, &connector->modes, verbose_prune); >> + drm_mode_prune_invalid(dev, &connector->modes, true); >> + /* >> + * Displayport spec section 5.2.1.2 ("Video Timing Format") says >> that >> + * all detachable sinks shall support 640x480 @60Hz as a fail safe >> + * mode. If all modes were pruned, perhaps because they need more >> + * lanes or a higher pixel clock than available, at least try to add >> + * in 640x480. >> + */ >> + if (list_empty(&connector->modes) && >> + connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) { >> + count = drm_add_modes_noedid(connector, 640, 480); >> + if (_drm_helper_update_and_validate(connector, maxX, maxY, >> &ctx)) { >> + drm_modeset_backoff(&ctx); >> + goto retry; > > Do we need another retry here? This will again repeat everything from > get_modes(). > The fact that we are hitting this code is because we have already tried > that and this is already a second-pass. So I think another retry isnt > needed? This will help cover the case of 4.2.2.6 but not fix 4.2.2.1. For 4.2.2.1, we will have 0 modes and so the original DRM fwk code of adding all modes <= 1024x768 will kick in. Now, in that list, we will still need to pick/mark 640x480 as the preferred mode. We still need IGT for that. So yes, this will cover one of the test but not the other. > >> + } >> + drm_mode_prune_invalid(dev, &connector->modes, true); >> + } >> + >> +exit: >> drm_modeset_drop_locks(&ctx); >> drm_modeset_acquire_fini(&ctx);
Hi, On Tue, Apr 26, 2022 at 12:16 PM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > > Hi Doug > > One minor comment below. > > But otherwise, looking at this change this should work for us acc to me. > > We will test this out with our equipment and then provide R-b. > > Thanks > > Abhinav > On 4/26/2022 11:46 AM, Douglas Anderson wrote: > > As per Displayport spec section 5.2.1.2 ("Video Timing Format") says > > that all detachable sinks shall support 640x480 @60Hz as a fail safe > > mode. > > > > A DP compliance test expected us to utilize the above fact when all > > modes it presented to the DP source were not achievable. It presented > > only modes that would be achievable with more lanes and/or higher > > speeds than we had available and expected that when we couldn't do > > that then we'd fall back to 640x480 even though it didn't advertise > > this size. > > > > In order to pass the compliance test (and also support any users who > > might fall into a similar situation with their display), we need to > > add 640x480 into the list of modes. However, we don't want to add > > 640x480 all the time. Despite the fact that the DP spec says all sinks > > _shall support_ 640x480, they're not guaranteed to support it > > _well_. Continuing to read the spec you can see that the display is > > not required to really treat 640x480 equal to all the other modes. It > > doesn't need to scale or anything--just display the pixels somehow for > > failsafe purposes. It should also be noted that it's not hard to find > > a display hooked up via DisplayPort that _doesn't_ support 640x480 at > > all. The HP ZR30w screen I'm sitting in front of has a native DP port > > and doesn't work at 640x480. I also plugged in a tiny 800x480 HDMI > > display via a DP to HDMI adapter and that screen definitely doesn't > > support 640x480. > > > > As a compromise solution, let's only add the 640x480 mode if: > > * We're on DP. > > * All other modes have been pruned. > > > > This acknowledges that 640x480 might not be the best mode to use but, > > since sinks are _supposed_ to support it, we will at least fall back > > to it if there's nothing else. > > > > Note that we _don't_ add higher resolution modes like 1024x768 in this > > case. We only add those modes for a failed EDID read where we have no > > idea what's going on. In the case where we've pruned all modes then > > instead we only want 640x480 which is the only defined "Fail Safe" > > resolution. > > > > This patch originated in response to Kuogee Hsieh's patch [1]. > > > > [1] https://lore.kernel.org/r/1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com > > > > Signed-off-by: Douglas Anderson <dianders@chromium.org> > > --- > > > > drivers/gpu/drm/drm_probe_helper.c | 26 +++++++++++++++++++++----- > > 1 file changed, 21 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c > > index 819225629010..90cd46cbfec1 100644 > > --- a/drivers/gpu/drm/drm_probe_helper.c > > +++ b/drivers/gpu/drm/drm_probe_helper.c > > @@ -476,7 +476,6 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector, > > const struct drm_connector_helper_funcs *connector_funcs = > > connector->helper_private; > > int count = 0, ret; > > - bool verbose_prune = true; > > enum drm_connector_status old_status; > > struct drm_modeset_acquire_ctx ctx; > > > > @@ -556,8 +555,8 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector, > > DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n", > > connector->base.id, connector->name); > > drm_connector_update_edid_property(connector, NULL); > > - verbose_prune = false; > > - goto prune; > > + drm_mode_prune_invalid(dev, &connector->modes, false); > > + goto exit; > > } > > > > count = (*connector_funcs->get_modes)(connector); > > @@ -580,9 +579,26 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector, > > } > > } > > > > -prune: > > - drm_mode_prune_invalid(dev, &connector->modes, verbose_prune); > > + drm_mode_prune_invalid(dev, &connector->modes, true); > > > > + /* > > + * Displayport spec section 5.2.1.2 ("Video Timing Format") says that > > + * all detachable sinks shall support 640x480 @60Hz as a fail safe > > + * mode. If all modes were pruned, perhaps because they need more > > + * lanes or a higher pixel clock than available, at least try to add > > + * in 640x480. > > + */ > > + if (list_empty(&connector->modes) && > > + connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) { > > + count = drm_add_modes_noedid(connector, 640, 480); > > + if (_drm_helper_update_and_validate(connector, maxX, maxY, &ctx)) { > > + drm_modeset_backoff(&ctx); > > + goto retry; > > Do we need another retry here? This will again repeat everything from > get_modes(). > The fact that we are hitting this code is because we have already tried > that and this is already a second-pass. So I think another retry isnt > needed? The retry is still needed. This gets into the whole wait-wound mutexes that DRM uses, right? Any time we detect deadlock we release all of our locks and start from scratch. That's still possible here. -Doug
Hi, On Tue, Apr 26, 2022 at 12:20 PM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > > Missed one more comment. > > On 4/26/2022 12:16 PM, Abhinav Kumar wrote: > > Hi Doug > > > > One minor comment below. > > > > But otherwise, looking at this change this should work for us acc to me. > > > > We will test this out with our equipment and then provide R-b. > > > > Thanks > > > > Abhinav > > On 4/26/2022 11:46 AM, Douglas Anderson wrote: > >> As per Displayport spec section 5.2.1.2 ("Video Timing Format") says > >> that all detachable sinks shall support 640x480 @60Hz as a fail safe > >> mode. > >> > >> A DP compliance test expected us to utilize the above fact when all > >> modes it presented to the DP source were not achievable. It presented > >> only modes that would be achievable with more lanes and/or higher > >> speeds than we had available and expected that when we couldn't do > >> that then we'd fall back to 640x480 even though it didn't advertise > >> this size. > >> > >> In order to pass the compliance test (and also support any users who > >> might fall into a similar situation with their display), we need to > >> add 640x480 into the list of modes. However, we don't want to add > >> 640x480 all the time. Despite the fact that the DP spec says all sinks > >> _shall support_ 640x480, they're not guaranteed to support it > >> _well_. Continuing to read the spec you can see that the display is > >> not required to really treat 640x480 equal to all the other modes. It > >> doesn't need to scale or anything--just display the pixels somehow for > >> failsafe purposes. It should also be noted that it's not hard to find > >> a display hooked up via DisplayPort that _doesn't_ support 640x480 at > >> all. The HP ZR30w screen I'm sitting in front of has a native DP port > >> and doesn't work at 640x480. I also plugged in a tiny 800x480 HDMI > >> display via a DP to HDMI adapter and that screen definitely doesn't > >> support 640x480. > >> > >> As a compromise solution, let's only add the 640x480 mode if: > >> * We're on DP. > >> * All other modes have been pruned. > >> > >> This acknowledges that 640x480 might not be the best mode to use but, > >> since sinks are _supposed_ to support it, we will at least fall back > >> to it if there's nothing else. > >> > >> Note that we _don't_ add higher resolution modes like 1024x768 in this > >> case. We only add those modes for a failed EDID read where we have no > >> idea what's going on. In the case where we've pruned all modes then > >> instead we only want 640x480 which is the only defined "Fail Safe" > >> resolution. > >> > >> This patch originated in response to Kuogee Hsieh's patch [1]. > >> > >> [1] > >> https://lore.kernel.org/r/1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com > >> > >> > >> Signed-off-by: Douglas Anderson <dianders@chromium.org> > >> --- > >> > >> drivers/gpu/drm/drm_probe_helper.c | 26 +++++++++++++++++++++----- > >> 1 file changed, 21 insertions(+), 5 deletions(-) > >> > >> diff --git a/drivers/gpu/drm/drm_probe_helper.c > >> b/drivers/gpu/drm/drm_probe_helper.c > >> index 819225629010..90cd46cbfec1 100644 > >> --- a/drivers/gpu/drm/drm_probe_helper.c > >> +++ b/drivers/gpu/drm/drm_probe_helper.c > >> @@ -476,7 +476,6 @@ int drm_helper_probe_single_connector_modes(struct > >> drm_connector *connector, > >> const struct drm_connector_helper_funcs *connector_funcs = > >> connector->helper_private; > >> int count = 0, ret; > >> - bool verbose_prune = true; > >> enum drm_connector_status old_status; > >> struct drm_modeset_acquire_ctx ctx; > >> @@ -556,8 +555,8 @@ int drm_helper_probe_single_connector_modes(struct > >> drm_connector *connector, > >> DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n", > >> connector->base.id, connector->name); > >> drm_connector_update_edid_property(connector, NULL); > >> - verbose_prune = false; > >> - goto prune; > >> + drm_mode_prune_invalid(dev, &connector->modes, false); > >> + goto exit; > >> } > >> count = (*connector_funcs->get_modes)(connector); > >> @@ -580,9 +579,26 @@ int > >> drm_helper_probe_single_connector_modes(struct drm_connector *connector, > >> } > >> } > >> -prune: > >> - drm_mode_prune_invalid(dev, &connector->modes, verbose_prune); > >> + drm_mode_prune_invalid(dev, &connector->modes, true); > >> + /* > >> + * Displayport spec section 5.2.1.2 ("Video Timing Format") says > >> that > >> + * all detachable sinks shall support 640x480 @60Hz as a fail safe > >> + * mode. If all modes were pruned, perhaps because they need more > >> + * lanes or a higher pixel clock than available, at least try to add > >> + * in 640x480. > >> + */ > >> + if (list_empty(&connector->modes) && > >> + connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) { > >> + count = drm_add_modes_noedid(connector, 640, 480); > >> + if (_drm_helper_update_and_validate(connector, maxX, maxY, > >> &ctx)) { > >> + drm_modeset_backoff(&ctx); > >> + goto retry; > > > > Do we need another retry here? This will again repeat everything from > > get_modes(). > > The fact that we are hitting this code is because we have already tried > > that and this is already a second-pass. So I think another retry isnt > > needed? > > This will help cover the case of 4.2.2.6 but not fix 4.2.2.1. > > For 4.2.2.1, we will have 0 modes and so the original DRM fwk code of > adding all modes <= 1024x768 will kick in. > > Now, in that list, we will still need to pick/mark 640x480 as the > preferred mode. > > We still need IGT for that. Are you sure you don't have those backwards? It seems like 4.2.2.6 is the test case dealing with corrupt EDID and that's the one that will still be broken, no? ...and corrupt EDID is still the case where we have 0 modes. In any case, let's see what people think about: https://lore.kernel.org/r/20220426132121.RFC.1.I31ec454f8d4ffce51a7708a8092f8a6f9c929092@changeid I've marked that one as RFC just because it seems like a bigger change to existing behavior, though it still seems correct to me. NOTE: reading 4.2.2.6 more closely, it actually looks as if we're actually supposed to be able to try various video modes one at a time until we find one that works (or land on 640x480). Seems as if we're supposed to be able to try the higher resolutions one at a time and we can tell whether the sink "accepted" it by seeing if SINK_STATUS goes to 1? I have no idea how that works with all the Linux APIs, though. -Doug
On 4/26/2022 1:26 PM, Doug Anderson wrote: > Hi, > > On Tue, Apr 26, 2022 at 12:20 PM Abhinav Kumar > <quic_abhinavk@quicinc.com> wrote: >> >> Missed one more comment. >> >> On 4/26/2022 12:16 PM, Abhinav Kumar wrote: >>> Hi Doug >>> >>> One minor comment below. >>> >>> But otherwise, looking at this change this should work for us acc to me. >>> >>> We will test this out with our equipment and then provide R-b. >>> >>> Thanks >>> >>> Abhinav >>> On 4/26/2022 11:46 AM, Douglas Anderson wrote: >>>> As per Displayport spec section 5.2.1.2 ("Video Timing Format") says >>>> that all detachable sinks shall support 640x480 @60Hz as a fail safe >>>> mode. >>>> >>>> A DP compliance test expected us to utilize the above fact when all >>>> modes it presented to the DP source were not achievable. It presented >>>> only modes that would be achievable with more lanes and/or higher >>>> speeds than we had available and expected that when we couldn't do >>>> that then we'd fall back to 640x480 even though it didn't advertise >>>> this size. >>>> >>>> In order to pass the compliance test (and also support any users who >>>> might fall into a similar situation with their display), we need to >>>> add 640x480 into the list of modes. However, we don't want to add >>>> 640x480 all the time. Despite the fact that the DP spec says all sinks >>>> _shall support_ 640x480, they're not guaranteed to support it >>>> _well_. Continuing to read the spec you can see that the display is >>>> not required to really treat 640x480 equal to all the other modes. It >>>> doesn't need to scale or anything--just display the pixels somehow for >>>> failsafe purposes. It should also be noted that it's not hard to find >>>> a display hooked up via DisplayPort that _doesn't_ support 640x480 at >>>> all. The HP ZR30w screen I'm sitting in front of has a native DP port >>>> and doesn't work at 640x480. I also plugged in a tiny 800x480 HDMI >>>> display via a DP to HDMI adapter and that screen definitely doesn't >>>> support 640x480. >>>> >>>> As a compromise solution, let's only add the 640x480 mode if: >>>> * We're on DP. >>>> * All other modes have been pruned. >>>> >>>> This acknowledges that 640x480 might not be the best mode to use but, >>>> since sinks are _supposed_ to support it, we will at least fall back >>>> to it if there's nothing else. >>>> >>>> Note that we _don't_ add higher resolution modes like 1024x768 in this >>>> case. We only add those modes for a failed EDID read where we have no >>>> idea what's going on. In the case where we've pruned all modes then >>>> instead we only want 640x480 which is the only defined "Fail Safe" >>>> resolution. >>>> >>>> This patch originated in response to Kuogee Hsieh's patch [1]. >>>> >>>> [1] >>>> https://lore.kernel.org/r/1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com >>>> >>>> >>>> Signed-off-by: Douglas Anderson <dianders@chromium.org> >>>> --- >>>> >>>> drivers/gpu/drm/drm_probe_helper.c | 26 +++++++++++++++++++++----- >>>> 1 file changed, 21 insertions(+), 5 deletions(-) >>>> >>>> diff --git a/drivers/gpu/drm/drm_probe_helper.c >>>> b/drivers/gpu/drm/drm_probe_helper.c >>>> index 819225629010..90cd46cbfec1 100644 >>>> --- a/drivers/gpu/drm/drm_probe_helper.c >>>> +++ b/drivers/gpu/drm/drm_probe_helper.c >>>> @@ -476,7 +476,6 @@ int drm_helper_probe_single_connector_modes(struct >>>> drm_connector *connector, >>>> const struct drm_connector_helper_funcs *connector_funcs = >>>> connector->helper_private; >>>> int count = 0, ret; >>>> - bool verbose_prune = true; >>>> enum drm_connector_status old_status; >>>> struct drm_modeset_acquire_ctx ctx; >>>> @@ -556,8 +555,8 @@ int drm_helper_probe_single_connector_modes(struct >>>> drm_connector *connector, >>>> DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n", >>>> connector->base.id, connector->name); >>>> drm_connector_update_edid_property(connector, NULL); >>>> - verbose_prune = false; >>>> - goto prune; >>>> + drm_mode_prune_invalid(dev, &connector->modes, false); >>>> + goto exit; >>>> } >>>> count = (*connector_funcs->get_modes)(connector); >>>> @@ -580,9 +579,26 @@ int >>>> drm_helper_probe_single_connector_modes(struct drm_connector *connector, >>>> } >>>> } >>>> -prune: >>>> - drm_mode_prune_invalid(dev, &connector->modes, verbose_prune); >>>> + drm_mode_prune_invalid(dev, &connector->modes, true); >>>> + /* >>>> + * Displayport spec section 5.2.1.2 ("Video Timing Format") says >>>> that >>>> + * all detachable sinks shall support 640x480 @60Hz as a fail safe >>>> + * mode. If all modes were pruned, perhaps because they need more >>>> + * lanes or a higher pixel clock than available, at least try to add >>>> + * in 640x480. >>>> + */ >>>> + if (list_empty(&connector->modes) && >>>> + connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) { >>>> + count = drm_add_modes_noedid(connector, 640, 480); >>>> + if (_drm_helper_update_and_validate(connector, maxX, maxY, >>>> &ctx)) { >>>> + drm_modeset_backoff(&ctx); >>>> + goto retry; >>> >>> Do we need another retry here? This will again repeat everything from >>> get_modes(). >>> The fact that we are hitting this code is because we have already tried >>> that and this is already a second-pass. So I think another retry isnt >>> needed? >> >> This will help cover the case of 4.2.2.6 but not fix 4.2.2.1. >> >> For 4.2.2.1, we will have 0 modes and so the original DRM fwk code of >> adding all modes <= 1024x768 will kick in. >> >> Now, in that list, we will still need to pick/mark 640x480 as the >> preferred mode. >> >> We still need IGT for that. > > Are you sure you don't have those backwards? It seems like 4.2.2.6 is > the test case dealing with corrupt EDID and that's the one that will > still be broken, no? ...and corrupt EDID is still the case where we > have 0 modes. Yes indeed, sorry, I did have the numbers backwards. 4.2.2.6 will still be broken. > > In any case, let's see what people think about: > > https://lore.kernel.org/r/20220426132121.RFC.1.I31ec454f8d4ffce51a7708a8092f8a6f9c929092@changeid Yes sure. If it gets accepted, it will save us some IGT work. > > I've marked that one as RFC just because it seems like a bigger change > to existing behavior, though it still seems correct to me. > > NOTE: reading 4.2.2.6 more closely, it actually looks as if we're > actually supposed to be able to try various video modes one at a time > until we find one that works (or land on 640x480). Seems as if we're > supposed to be able to try the higher resolutions one at a time and we > can tell whether the sink "accepted" it by seeing if SINK_STATUS goes > to 1? I have no idea how that works with all the Linux APIs, though. > hmmm .... our equipment throws a warning if we dont sent 640x480. So perhaps just go with the "or land on 640x480" option. 0006.392.232: [WARNING] Source DUT failed to transmit a video stream using fail-safe mode 0006.392.491: Received 1344 Htotal differs from fail-safe 800 0006.392.621: Received 1024 Hactive differs from fail-safe 640 0006.392.750: Received 296 Hstart differs from fail-safe 144 0006.392.868: Received 136 Hsync width differs from fail-safe 96 0006.392.975: Received 806 Vtotal differs from fail-safe 525 0006.393.099: Received 768 Vactive differs from fail-safe 480 0006.393.229: Received 6 Vsync width differs from fail-safe 2 > -Doug
Hi, On Tue, Apr 26, 2022 at 2:11 PM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > > > > On 4/26/2022 1:26 PM, Doug Anderson wrote: > > Hi, > > > > On Tue, Apr 26, 2022 at 12:20 PM Abhinav Kumar > > <quic_abhinavk@quicinc.com> wrote: > >> > >> Missed one more comment. > >> > >> On 4/26/2022 12:16 PM, Abhinav Kumar wrote: > >>> Hi Doug > >>> > >>> One minor comment below. > >>> > >>> But otherwise, looking at this change this should work for us acc to me. > >>> > >>> We will test this out with our equipment and then provide R-b. > >>> > >>> Thanks > >>> > >>> Abhinav > >>> On 4/26/2022 11:46 AM, Douglas Anderson wrote: > >>>> As per Displayport spec section 5.2.1.2 ("Video Timing Format") says > >>>> that all detachable sinks shall support 640x480 @60Hz as a fail safe > >>>> mode. > >>>> > >>>> A DP compliance test expected us to utilize the above fact when all > >>>> modes it presented to the DP source were not achievable. It presented > >>>> only modes that would be achievable with more lanes and/or higher > >>>> speeds than we had available and expected that when we couldn't do > >>>> that then we'd fall back to 640x480 even though it didn't advertise > >>>> this size. > >>>> > >>>> In order to pass the compliance test (and also support any users who > >>>> might fall into a similar situation with their display), we need to > >>>> add 640x480 into the list of modes. However, we don't want to add > >>>> 640x480 all the time. Despite the fact that the DP spec says all sinks > >>>> _shall support_ 640x480, they're not guaranteed to support it > >>>> _well_. Continuing to read the spec you can see that the display is > >>>> not required to really treat 640x480 equal to all the other modes. It > >>>> doesn't need to scale or anything--just display the pixels somehow for > >>>> failsafe purposes. It should also be noted that it's not hard to find > >>>> a display hooked up via DisplayPort that _doesn't_ support 640x480 at > >>>> all. The HP ZR30w screen I'm sitting in front of has a native DP port > >>>> and doesn't work at 640x480. I also plugged in a tiny 800x480 HDMI > >>>> display via a DP to HDMI adapter and that screen definitely doesn't > >>>> support 640x480. > >>>> > >>>> As a compromise solution, let's only add the 640x480 mode if: > >>>> * We're on DP. > >>>> * All other modes have been pruned. > >>>> > >>>> This acknowledges that 640x480 might not be the best mode to use but, > >>>> since sinks are _supposed_ to support it, we will at least fall back > >>>> to it if there's nothing else. > >>>> > >>>> Note that we _don't_ add higher resolution modes like 1024x768 in this > >>>> case. We only add those modes for a failed EDID read where we have no > >>>> idea what's going on. In the case where we've pruned all modes then > >>>> instead we only want 640x480 which is the only defined "Fail Safe" > >>>> resolution. > >>>> > >>>> This patch originated in response to Kuogee Hsieh's patch [1]. > >>>> > >>>> [1] > >>>> https://lore.kernel.org/r/1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com > >>>> > >>>> > >>>> Signed-off-by: Douglas Anderson <dianders@chromium.org> > >>>> --- > >>>> > >>>> drivers/gpu/drm/drm_probe_helper.c | 26 +++++++++++++++++++++----- > >>>> 1 file changed, 21 insertions(+), 5 deletions(-) > >>>> > >>>> diff --git a/drivers/gpu/drm/drm_probe_helper.c > >>>> b/drivers/gpu/drm/drm_probe_helper.c > >>>> index 819225629010..90cd46cbfec1 100644 > >>>> --- a/drivers/gpu/drm/drm_probe_helper.c > >>>> +++ b/drivers/gpu/drm/drm_probe_helper.c > >>>> @@ -476,7 +476,6 @@ int drm_helper_probe_single_connector_modes(struct > >>>> drm_connector *connector, > >>>> const struct drm_connector_helper_funcs *connector_funcs = > >>>> connector->helper_private; > >>>> int count = 0, ret; > >>>> - bool verbose_prune = true; > >>>> enum drm_connector_status old_status; > >>>> struct drm_modeset_acquire_ctx ctx; > >>>> @@ -556,8 +555,8 @@ int drm_helper_probe_single_connector_modes(struct > >>>> drm_connector *connector, > >>>> DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n", > >>>> connector->base.id, connector->name); > >>>> drm_connector_update_edid_property(connector, NULL); > >>>> - verbose_prune = false; > >>>> - goto prune; > >>>> + drm_mode_prune_invalid(dev, &connector->modes, false); > >>>> + goto exit; > >>>> } > >>>> count = (*connector_funcs->get_modes)(connector); > >>>> @@ -580,9 +579,26 @@ int > >>>> drm_helper_probe_single_connector_modes(struct drm_connector *connector, > >>>> } > >>>> } > >>>> -prune: > >>>> - drm_mode_prune_invalid(dev, &connector->modes, verbose_prune); > >>>> + drm_mode_prune_invalid(dev, &connector->modes, true); > >>>> + /* > >>>> + * Displayport spec section 5.2.1.2 ("Video Timing Format") says > >>>> that > >>>> + * all detachable sinks shall support 640x480 @60Hz as a fail safe > >>>> + * mode. If all modes were pruned, perhaps because they need more > >>>> + * lanes or a higher pixel clock than available, at least try to add > >>>> + * in 640x480. > >>>> + */ > >>>> + if (list_empty(&connector->modes) && > >>>> + connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) { > >>>> + count = drm_add_modes_noedid(connector, 640, 480); > >>>> + if (_drm_helper_update_and_validate(connector, maxX, maxY, > >>>> &ctx)) { > >>>> + drm_modeset_backoff(&ctx); > >>>> + goto retry; > >>> > >>> Do we need another retry here? This will again repeat everything from > >>> get_modes(). > >>> The fact that we are hitting this code is because we have already tried > >>> that and this is already a second-pass. So I think another retry isnt > >>> needed? > >> > >> This will help cover the case of 4.2.2.6 but not fix 4.2.2.1. > >> > >> For 4.2.2.1, we will have 0 modes and so the original DRM fwk code of > >> adding all modes <= 1024x768 will kick in. > >> > >> Now, in that list, we will still need to pick/mark 640x480 as the > >> preferred mode. > >> > >> We still need IGT for that. > > > > Are you sure you don't have those backwards? It seems like 4.2.2.6 is > > the test case dealing with corrupt EDID and that's the one that will > > still be broken, no? ...and corrupt EDID is still the case where we > > have 0 modes. > > Yes indeed, sorry, I did have the numbers backwards. > 4.2.2.6 will still be broken. > > > > > In any case, let's see what people think about: > > > > https://lore.kernel.org/r/20220426132121.RFC.1.I31ec454f8d4ffce51a7708a8092f8a6f9c929092@changeid > > Yes sure. If it gets accepted, it will save us some IGT work. > > > > > I've marked that one as RFC just because it seems like a bigger change > > to existing behavior, though it still seems correct to me. > > > > NOTE: reading 4.2.2.6 more closely, it actually looks as if we're > > actually supposed to be able to try various video modes one at a time > > until we find one that works (or land on 640x480). Seems as if we're > > supposed to be able to try the higher resolutions one at a time and we > > can tell whether the sink "accepted" it by seeing if SINK_STATUS goes > > to 1? I have no idea how that works with all the Linux APIs, though. > > > > hmmm .... our equipment throws a warning if we dont sent 640x480. So > perhaps just go with the "or land on 640x480" option. > > 0006.392.232: [WARNING] Source DUT failed to transmit a video stream > using fail-safe mode > 0006.392.491: Received 1344 Htotal differs from fail-safe 800 > 0006.392.621: Received 1024 Hactive differs from fail-safe 640 > 0006.392.750: Received 296 Hstart differs from fail-safe 144 > 0006.392.868: Received 136 Hsync width differs from fail-safe 96 > 0006.392.975: Received 806 Vtotal differs from fail-safe 525 > 0006.393.099: Received 768 Vactive differs from fail-safe 480 > 0006.393.229: Received 6 Vsync width differs from fail-safe 2 Do you actually have code to implement the checking of SINK_STATUS? I'm not aware of how that would work in Linux, which is why just defaulting to 640x480 seems like a reasonable thing to do for now. The test case actually says that you're allowed to try clock rates one at a time (polling SINK_STATUS in DPCT) as long as you don't spend more than 5 seconds on each clock rate. According to the test case if you never saw SINK_STATUS in DPCT go to 1 then you should end at 640x480.
Tested-by: Kuogee Hsieh <quic_khsieh@quicinc.com> On 4/26/2022 2:17 PM, Doug Anderson wrote: > Hi, > > On Tue, Apr 26, 2022 at 2:11 PM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: >> >> >> On 4/26/2022 1:26 PM, Doug Anderson wrote: >>> Hi, >>> >>> On Tue, Apr 26, 2022 at 12:20 PM Abhinav Kumar >>> <quic_abhinavk@quicinc.com> wrote: >>>> Missed one more comment. >>>> >>>> On 4/26/2022 12:16 PM, Abhinav Kumar wrote: >>>>> Hi Doug >>>>> >>>>> One minor comment below. >>>>> >>>>> But otherwise, looking at this change this should work for us acc to me. >>>>> >>>>> We will test this out with our equipment and then provide R-b. >>>>> >>>>> Thanks >>>>> >>>>> Abhinav >>>>> On 4/26/2022 11:46 AM, Douglas Anderson wrote: >>>>>> As per Displayport spec section 5.2.1.2 ("Video Timing Format") says >>>>>> that all detachable sinks shall support 640x480 @60Hz as a fail safe >>>>>> mode. >>>>>> >>>>>> A DP compliance test expected us to utilize the above fact when all >>>>>> modes it presented to the DP source were not achievable. It presented >>>>>> only modes that would be achievable with more lanes and/or higher >>>>>> speeds than we had available and expected that when we couldn't do >>>>>> that then we'd fall back to 640x480 even though it didn't advertise >>>>>> this size. >>>>>> >>>>>> In order to pass the compliance test (and also support any users who >>>>>> might fall into a similar situation with their display), we need to >>>>>> add 640x480 into the list of modes. However, we don't want to add >>>>>> 640x480 all the time. Despite the fact that the DP spec says all sinks >>>>>> _shall support_ 640x480, they're not guaranteed to support it >>>>>> _well_. Continuing to read the spec you can see that the display is >>>>>> not required to really treat 640x480 equal to all the other modes. It >>>>>> doesn't need to scale or anything--just display the pixels somehow for >>>>>> failsafe purposes. It should also be noted that it's not hard to find >>>>>> a display hooked up via DisplayPort that _doesn't_ support 640x480 at >>>>>> all. The HP ZR30w screen I'm sitting in front of has a native DP port >>>>>> and doesn't work at 640x480. I also plugged in a tiny 800x480 HDMI >>>>>> display via a DP to HDMI adapter and that screen definitely doesn't >>>>>> support 640x480. >>>>>> >>>>>> As a compromise solution, let's only add the 640x480 mode if: >>>>>> * We're on DP. >>>>>> * All other modes have been pruned. >>>>>> >>>>>> This acknowledges that 640x480 might not be the best mode to use but, >>>>>> since sinks are _supposed_ to support it, we will at least fall back >>>>>> to it if there's nothing else. >>>>>> >>>>>> Note that we _don't_ add higher resolution modes like 1024x768 in this >>>>>> case. We only add those modes for a failed EDID read where we have no >>>>>> idea what's going on. In the case where we've pruned all modes then >>>>>> instead we only want 640x480 which is the only defined "Fail Safe" >>>>>> resolution. >>>>>> >>>>>> This patch originated in response to Kuogee Hsieh's patch [1]. >>>>>> >>>>>> [1] >>>>>> https://lore.kernel.org/r/1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com >>>>>> >>>>>> >>>>>> Signed-off-by: Douglas Anderson <dianders@chromium.org> >>>>>> --- >>>>>> >>>>>> drivers/gpu/drm/drm_probe_helper.c | 26 +++++++++++++++++++++----- >>>>>> 1 file changed, 21 insertions(+), 5 deletions(-) >>>>>> >>>>>> diff --git a/drivers/gpu/drm/drm_probe_helper.c >>>>>> b/drivers/gpu/drm/drm_probe_helper.c >>>>>> index 819225629010..90cd46cbfec1 100644 >>>>>> --- a/drivers/gpu/drm/drm_probe_helper.c >>>>>> +++ b/drivers/gpu/drm/drm_probe_helper.c >>>>>> @@ -476,7 +476,6 @@ int drm_helper_probe_single_connector_modes(struct >>>>>> drm_connector *connector, >>>>>> const struct drm_connector_helper_funcs *connector_funcs = >>>>>> connector->helper_private; >>>>>> int count = 0, ret; >>>>>> - bool verbose_prune = true; >>>>>> enum drm_connector_status old_status; >>>>>> struct drm_modeset_acquire_ctx ctx; >>>>>> @@ -556,8 +555,8 @@ int drm_helper_probe_single_connector_modes(struct >>>>>> drm_connector *connector, >>>>>> DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n", >>>>>> connector->base.id, connector->name); >>>>>> drm_connector_update_edid_property(connector, NULL); >>>>>> - verbose_prune = false; >>>>>> - goto prune; >>>>>> + drm_mode_prune_invalid(dev, &connector->modes, false); >>>>>> + goto exit; >>>>>> } >>>>>> count = (*connector_funcs->get_modes)(connector); >>>>>> @@ -580,9 +579,26 @@ int >>>>>> drm_helper_probe_single_connector_modes(struct drm_connector *connector, >>>>>> } >>>>>> } >>>>>> -prune: >>>>>> - drm_mode_prune_invalid(dev, &connector->modes, verbose_prune); >>>>>> + drm_mode_prune_invalid(dev, &connector->modes, true); >>>>>> + /* >>>>>> + * Displayport spec section 5.2.1.2 ("Video Timing Format") says >>>>>> that >>>>>> + * all detachable sinks shall support 640x480 @60Hz as a fail safe >>>>>> + * mode. If all modes were pruned, perhaps because they need more >>>>>> + * lanes or a higher pixel clock than available, at least try to add >>>>>> + * in 640x480. >>>>>> + */ >>>>>> + if (list_empty(&connector->modes) && >>>>>> + connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) { >>>>>> + count = drm_add_modes_noedid(connector, 640, 480); >>>>>> + if (_drm_helper_update_and_validate(connector, maxX, maxY, >>>>>> &ctx)) { >>>>>> + drm_modeset_backoff(&ctx); >>>>>> + goto retry; >>>>> Do we need another retry here? This will again repeat everything from >>>>> get_modes(). >>>>> The fact that we are hitting this code is because we have already tried >>>>> that and this is already a second-pass. So I think another retry isnt >>>>> needed? >>>> This will help cover the case of 4.2.2.6 but not fix 4.2.2.1. >>>> >>>> For 4.2.2.1, we will have 0 modes and so the original DRM fwk code of >>>> adding all modes <= 1024x768 will kick in. >>>> >>>> Now, in that list, we will still need to pick/mark 640x480 as the >>>> preferred mode. >>>> >>>> We still need IGT for that. >>> Are you sure you don't have those backwards? It seems like 4.2.2.6 is >>> the test case dealing with corrupt EDID and that's the one that will >>> still be broken, no? ...and corrupt EDID is still the case where we >>> have 0 modes. >> Yes indeed, sorry, I did have the numbers backwards. >> 4.2.2.6 will still be broken. >> >>> In any case, let's see what people think about: >>> >>> https://lore.kernel.org/r/20220426132121.RFC.1.I31ec454f8d4ffce51a7708a8092f8a6f9c929092@changeid >> Yes sure. If it gets accepted, it will save us some IGT work. >> >>> I've marked that one as RFC just because it seems like a bigger change >>> to existing behavior, though it still seems correct to me. >>> >>> NOTE: reading 4.2.2.6 more closely, it actually looks as if we're >>> actually supposed to be able to try various video modes one at a time >>> until we find one that works (or land on 640x480). Seems as if we're >>> supposed to be able to try the higher resolutions one at a time and we >>> can tell whether the sink "accepted" it by seeing if SINK_STATUS goes >>> to 1? I have no idea how that works with all the Linux APIs, though. >>> >> hmmm .... our equipment throws a warning if we dont sent 640x480. So >> perhaps just go with the "or land on 640x480" option. >> >> 0006.392.232: [WARNING] Source DUT failed to transmit a video stream >> using fail-safe mode >> 0006.392.491: Received 1344 Htotal differs from fail-safe 800 >> 0006.392.621: Received 1024 Hactive differs from fail-safe 640 >> 0006.392.750: Received 296 Hstart differs from fail-safe 144 >> 0006.392.868: Received 136 Hsync width differs from fail-safe 96 >> 0006.392.975: Received 806 Vtotal differs from fail-safe 525 >> 0006.393.099: Received 768 Vactive differs from fail-safe 480 >> 0006.393.229: Received 6 Vsync width differs from fail-safe 2 > Do you actually have code to implement the checking of SINK_STATUS? > I'm not aware of how that would work in Linux, which is why just > defaulting to 640x480 seems like a reasonable thing to do for now. The > test case actually says that you're allowed to try clock rates one at > a time (polling SINK_STATUS in DPCT) as long as you don't spend more > than 5 seconds on each clock rate. According to the test case if you > never saw SINK_STATUS in DPCT go to 1 then you should end at 640x480.
On Thu, 5 May 2022 at 20:30, Kuogee Hsieh <quic_khsieh@quicinc.com> wrote: > > > On 5/5/2022 10:20 AM, Abhinav Kumar wrote: > > Hi Doug > > > > On 5/5/2022 8:44 AM, Doug Anderson wrote: > >> Ville, > >> > >> On Tue, Apr 26, 2022 at 11:47 AM Douglas Anderson > >> <dianders@chromium.org> wrote: > >>> > >>> As per Displayport spec section 5.2.1.2 ("Video Timing Format") says > >>> that all detachable sinks shall support 640x480 @60Hz as a fail safe > >>> mode. > >>> > >>> A DP compliance test expected us to utilize the above fact when all > >>> modes it presented to the DP source were not achievable. It presented > >>> only modes that would be achievable with more lanes and/or higher > >>> speeds than we had available and expected that when we couldn't do > >>> that then we'd fall back to 640x480 even though it didn't advertise > >>> this size. > >>> > >>> In order to pass the compliance test (and also support any users who > >>> might fall into a similar situation with their display), we need to > >>> add 640x480 into the list of modes. However, we don't want to add > >>> 640x480 all the time. Despite the fact that the DP spec says all sinks > >>> _shall support_ 640x480, they're not guaranteed to support it > >>> _well_. Continuing to read the spec you can see that the display is > >>> not required to really treat 640x480 equal to all the other modes. It > >>> doesn't need to scale or anything--just display the pixels somehow for > >>> failsafe purposes. It should also be noted that it's not hard to find > >>> a display hooked up via DisplayPort that _doesn't_ support 640x480 at > >>> all. The HP ZR30w screen I'm sitting in front of has a native DP port > >>> and doesn't work at 640x480. I also plugged in a tiny 800x480 HDMI > >>> display via a DP to HDMI adapter and that screen definitely doesn't > >>> support 640x480. > >>> > >>> As a compromise solution, let's only add the 640x480 mode if: > >>> * We're on DP. > >>> * All other modes have been pruned. > >>> > >>> This acknowledges that 640x480 might not be the best mode to use but, > >>> since sinks are _supposed_ to support it, we will at least fall back > >>> to it if there's nothing else. > >>> > >>> Note that we _don't_ add higher resolution modes like 1024x768 in this > >>> case. We only add those modes for a failed EDID read where we have no > >>> idea what's going on. In the case where we've pruned all modes then > >>> instead we only want 640x480 which is the only defined "Fail Safe" > >>> resolution. > >>> > >>> This patch originated in response to Kuogee Hsieh's patch [1]. > >>> > >>> [1] > >>> https://lore.kernel.org/r/1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com > >>> > >>> Signed-off-by: Douglas Anderson <dianders@chromium.org> > >>> --- > >>> > >>> drivers/gpu/drm/drm_probe_helper.c | 26 +++++++++++++++++++++----- > >>> 1 file changed, 21 insertions(+), 5 deletions(-) > >> > >> I think this patch is fairly safe / non-controversial, but someone > >> suggested you might have an opinion on it and another patch I posted > >> recently [1] so I wanted to double-check. Just to be clear: I'm hoping > >> to land _both_ this patch and [1]. If you don't have an opinion, > >> that's OK too. > >> > >> Abhinav: I think maybe you're happy with this now? Would you be > >> willing to give a Reviewed-by? > > > > Yes, I have no concerns with this approach from DP spec standpoint and > > in addition, kuogee has tested this out and this does help us to pass > > the tests. > > > > Although, I might be missing some historical context on why this is > > not already done. > > > > But apart from that, LGTM. Hence, > > > > Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com> > > Tested-by: Kuogee Hsieh <quic_khsieh@quicinc.com> This line got wrong quotation level, so it will not be noticed by patchwork (and can be easily missed by other people too). Please resend. > >> > >> [1] > >> https://lore.kernel.org/r/20220426132121.RFC.1.I31ec454f8d4ffce51a7708a8092f8a6f9c929092@changeid > >> > >> -Doug
On Tue, 26 Apr 2022 at 21:47, Douglas Anderson <dianders@chromium.org> wrote: > > As per Displayport spec section 5.2.1.2 ("Video Timing Format") says > that all detachable sinks shall support 640x480 @60Hz as a fail safe > mode. > > A DP compliance test expected us to utilize the above fact when all > modes it presented to the DP source were not achievable. It presented > only modes that would be achievable with more lanes and/or higher > speeds than we had available and expected that when we couldn't do > that then we'd fall back to 640x480 even though it didn't advertise > this size. > > In order to pass the compliance test (and also support any users who > might fall into a similar situation with their display), we need to > add 640x480 into the list of modes. However, we don't want to add > 640x480 all the time. Despite the fact that the DP spec says all sinks > _shall support_ 640x480, they're not guaranteed to support it > _well_. Continuing to read the spec you can see that the display is > not required to really treat 640x480 equal to all the other modes. It > doesn't need to scale or anything--just display the pixels somehow for > failsafe purposes. It should also be noted that it's not hard to find > a display hooked up via DisplayPort that _doesn't_ support 640x480 at > all. The HP ZR30w screen I'm sitting in front of has a native DP port > and doesn't work at 640x480. I also plugged in a tiny 800x480 HDMI > display via a DP to HDMI adapter and that screen definitely doesn't > support 640x480. > > As a compromise solution, let's only add the 640x480 mode if: > * We're on DP. > * All other modes have been pruned. > > This acknowledges that 640x480 might not be the best mode to use but, > since sinks are _supposed_ to support it, we will at least fall back > to it if there's nothing else. > > Note that we _don't_ add higher resolution modes like 1024x768 in this > case. We only add those modes for a failed EDID read where we have no > idea what's going on. In the case where we've pruned all modes then > instead we only want 640x480 which is the only defined "Fail Safe" > resolution. > > This patch originated in response to Kuogee Hsieh's patch [1]. > > [1] https://lore.kernel.org/r/1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com > > Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > --- > > drivers/gpu/drm/drm_probe_helper.c | 26 +++++++++++++++++++++----- > 1 file changed, 21 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c > index 819225629010..90cd46cbfec1 100644 > --- a/drivers/gpu/drm/drm_probe_helper.c > +++ b/drivers/gpu/drm/drm_probe_helper.c > @@ -476,7 +476,6 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector, > const struct drm_connector_helper_funcs *connector_funcs = > connector->helper_private; > int count = 0, ret; > - bool verbose_prune = true; > enum drm_connector_status old_status; > struct drm_modeset_acquire_ctx ctx; > > @@ -556,8 +555,8 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector, > DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n", > connector->base.id, connector->name); > drm_connector_update_edid_property(connector, NULL); > - verbose_prune = false; > - goto prune; > + drm_mode_prune_invalid(dev, &connector->modes, false); > + goto exit; > } > > count = (*connector_funcs->get_modes)(connector); > @@ -580,9 +579,26 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector, > } > } > > -prune: > - drm_mode_prune_invalid(dev, &connector->modes, verbose_prune); > + drm_mode_prune_invalid(dev, &connector->modes, true); > > + /* > + * Displayport spec section 5.2.1.2 ("Video Timing Format") says that > + * all detachable sinks shall support 640x480 @60Hz as a fail safe > + * mode. If all modes were pruned, perhaps because they need more > + * lanes or a higher pixel clock than available, at least try to add > + * in 640x480. > + */ > + if (list_empty(&connector->modes) && > + connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) { > + count = drm_add_modes_noedid(connector, 640, 480); > + if (_drm_helper_update_and_validate(connector, maxX, maxY, &ctx)) { > + drm_modeset_backoff(&ctx); > + goto retry; > + } > + drm_mode_prune_invalid(dev, &connector->modes, true); > + } > + > +exit: > drm_modeset_drop_locks(&ctx); > drm_modeset_acquire_fini(&ctx); > > -- > 2.36.0.rc2.479.g8af0fa9b8e-goog >
diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c index 819225629010..90cd46cbfec1 100644 --- a/drivers/gpu/drm/drm_probe_helper.c +++ b/drivers/gpu/drm/drm_probe_helper.c @@ -476,7 +476,6 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector, const struct drm_connector_helper_funcs *connector_funcs = connector->helper_private; int count = 0, ret; - bool verbose_prune = true; enum drm_connector_status old_status; struct drm_modeset_acquire_ctx ctx; @@ -556,8 +555,8 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector, DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n", connector->base.id, connector->name); drm_connector_update_edid_property(connector, NULL); - verbose_prune = false; - goto prune; + drm_mode_prune_invalid(dev, &connector->modes, false); + goto exit; } count = (*connector_funcs->get_modes)(connector); @@ -580,9 +579,26 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector, } } -prune: - drm_mode_prune_invalid(dev, &connector->modes, verbose_prune); + drm_mode_prune_invalid(dev, &connector->modes, true); + /* + * Displayport spec section 5.2.1.2 ("Video Timing Format") says that + * all detachable sinks shall support 640x480 @60Hz as a fail safe + * mode. If all modes were pruned, perhaps because they need more + * lanes or a higher pixel clock than available, at least try to add + * in 640x480. + */ + if (list_empty(&connector->modes) && + connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) { + count = drm_add_modes_noedid(connector, 640, 480); + if (_drm_helper_update_and_validate(connector, maxX, maxY, &ctx)) { + drm_modeset_backoff(&ctx); + goto retry; + } + drm_mode_prune_invalid(dev, &connector->modes, true); + } + +exit: drm_modeset_drop_locks(&ctx); drm_modeset_acquire_fini(&ctx);
As per Displayport spec section 5.2.1.2 ("Video Timing Format") says that all detachable sinks shall support 640x480 @60Hz as a fail safe mode. A DP compliance test expected us to utilize the above fact when all modes it presented to the DP source were not achievable. It presented only modes that would be achievable with more lanes and/or higher speeds than we had available and expected that when we couldn't do that then we'd fall back to 640x480 even though it didn't advertise this size. In order to pass the compliance test (and also support any users who might fall into a similar situation with their display), we need to add 640x480 into the list of modes. However, we don't want to add 640x480 all the time. Despite the fact that the DP spec says all sinks _shall support_ 640x480, they're not guaranteed to support it _well_. Continuing to read the spec you can see that the display is not required to really treat 640x480 equal to all the other modes. It doesn't need to scale or anything--just display the pixels somehow for failsafe purposes. It should also be noted that it's not hard to find a display hooked up via DisplayPort that _doesn't_ support 640x480 at all. The HP ZR30w screen I'm sitting in front of has a native DP port and doesn't work at 640x480. I also plugged in a tiny 800x480 HDMI display via a DP to HDMI adapter and that screen definitely doesn't support 640x480. As a compromise solution, let's only add the 640x480 mode if: * We're on DP. * All other modes have been pruned. This acknowledges that 640x480 might not be the best mode to use but, since sinks are _supposed_ to support it, we will at least fall back to it if there's nothing else. Note that we _don't_ add higher resolution modes like 1024x768 in this case. We only add those modes for a failed EDID read where we have no idea what's going on. In the case where we've pruned all modes then instead we only want 640x480 which is the only defined "Fail Safe" resolution. This patch originated in response to Kuogee Hsieh's patch [1]. [1] https://lore.kernel.org/r/1650671124-14030-1-git-send-email-quic_khsieh@quicinc.com Signed-off-by: Douglas Anderson <dianders@chromium.org> --- drivers/gpu/drm/drm_probe_helper.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-)