| Message ID | 20210317184901.4029798-4-imre.deak@intel.com |
|---|---|
| State | Accepted |
| Commit | ab03631087f5c296030dd86265ea02dcdacc6802 |
| Headers | show |
| Series | drm/i915: Fix DP LTTPR link training mode initialization | expand |
On Thu, Mar 18, 2021 at 08:00:10PM +0200, Ville Syrjälä wrote: > On Wed, Mar 17, 2021 at 08:49:01PM +0200, Imre Deak wrote: > > By the specification the 0xF0000 - 0xF02FF range is only valid if the > > LTTPR revision at 0xF0000 is at least 1.4. Disable the LTTPR support > > otherwise. > > > > Fixes: 7b2a4ab8b0ef ("drm/i915: Switch to LTTPR transparent mode link training") > > Cc: <stable@vger.kernel.org> # v5.11 > > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> > > Signed-off-by: Imre Deak <imre.deak@intel.com> > > --- > > .../gpu/drm/i915/display/intel_dp_link_training.c | 14 ++++++++++---- > > 1 file changed, 10 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c > > index d8d90903226f..d92eb192c89d 100644 > > --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c > > +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c > > @@ -100,17 +100,23 @@ static bool intel_dp_read_lttpr_common_caps(struct intel_dp *intel_dp) > > return false; > > > > if (drm_dp_read_lttpr_common_caps(&intel_dp->aux, > > - intel_dp->lttpr_common_caps) < 0) { > > - intel_dp_reset_lttpr_common_caps(intel_dp); > > - return false; > > - } > > + intel_dp->lttpr_common_caps) < 0) > > + goto reset_caps; > > BTW just noticed this oddball thing in the spec: > "DPTX shall read specific registers within the LTTPR field (DPCD > Addresses F0000h through F0004h; see Table 2-198) to determine > whether any LTTPR(s) are present and if so, how many. This read > shall be in the form of a 5-byte native AUX Read transaction." > > Why exactly 5 bytes? I have no idea. Doesn't really make sense. > Just wondering if we really need to respect that and some LTTPRs > would fsck things up if we read more... I pointed this out to spec people and the new version (2.1) will require this to be 8 bytes. But yes, I do hope no existing ones depend on this being 5 bytes. > Anyways > Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> > > > > > drm_dbg_kms(&dp_to_i915(intel_dp)->drm, > > "LTTPR common capabilities: %*ph\n", > > (int)sizeof(intel_dp->lttpr_common_caps), > > intel_dp->lttpr_common_caps); > > > > + /* The minimum value of LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV is 1.4 */ > > + if (intel_dp->lttpr_common_caps[0] < 0x14) > > + goto reset_caps; > > + > > return true; > > + > > +reset_caps: > > + intel_dp_reset_lttpr_common_caps(intel_dp); > > + return false; > > } > > > > static bool > > -- > > 2.25.1 > > -- > Ville Syrjälä > Intel
diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c index d8d90903226f..d92eb192c89d 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c @@ -100,17 +100,23 @@ static bool intel_dp_read_lttpr_common_caps(struct intel_dp *intel_dp) return false; if (drm_dp_read_lttpr_common_caps(&intel_dp->aux, - intel_dp->lttpr_common_caps) < 0) { - intel_dp_reset_lttpr_common_caps(intel_dp); - return false; - } + intel_dp->lttpr_common_caps) < 0) + goto reset_caps; drm_dbg_kms(&dp_to_i915(intel_dp)->drm, "LTTPR common capabilities: %*ph\n", (int)sizeof(intel_dp->lttpr_common_caps), intel_dp->lttpr_common_caps); + /* The minimum value of LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV is 1.4 */ + if (intel_dp->lttpr_common_caps[0] < 0x14) + goto reset_caps; + return true; + +reset_caps: + intel_dp_reset_lttpr_common_caps(intel_dp); + return false; } static bool
By the specification the 0xF0000 - 0xF02FF range is only valid if the LTTPR revision at 0xF0000 is at least 1.4. Disable the LTTPR support otherwise. Fixes: 7b2a4ab8b0ef ("drm/i915: Switch to LTTPR transparent mode link training") Cc: <stable@vger.kernel.org> # v5.11 Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by: Imre Deak <imre.deak@intel.com> --- .../gpu/drm/i915/display/intel_dp_link_training.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)