| Message ID | 20250212-sdm845_dp-v2-1-4954e51458f4@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,1/2] drm/msm/dp: Disable wide bus support for SDM845 | expand |
On 2/12/2025 3:41 PM, Marijn Suijten wrote: > On 2025-02-12 15:03:46, James A. MacInnes wrote: >> SDM845 DPU hardware is rev 4.0.0 per hardware documents. >> Original patch to enable wide_bus operation did not take into account >> the SDM845 and it got carried over by accident. >> >> - Incorrect setting caused inoperable DisplayPort. >> - Corrected by separating SDM845 into its own descriptor. > > If anything I'd have appreciated to see our conversation in v1 pasted here > verbatim which is of the right verbosity to explain this. I can't do much with > a list of two items. > > I don't have a clearer way of explaining what all I find confusing about this > description, so let me propose what I would have written if this was my patch > instead: > > When widebus was enabled for DisplayPort in commit c7c412202623 ("drm/msm/dp: > enable widebus on all relevant chipsets") it was clarified that it is only > supported on DPU 5.0.0 onwards which includes SC7180 on DPU revision 6.2. > However, this patch missed that the description structure for SC7180 is also > reused for SDM845 (because of identical io_start address) which is only DPU > 4.0.0, leading to a wrongly enbled widebus feature and corruption on that > platform. > > Create a separate msm_dp_desc_sdm845 structure for this SoC compatible, > with the wide_bus_supported flag turned off. > > Note that no other DisplayPort compatibles currently exist for SoCs older > than DPU 4.0.0 besides SDM845. > Yes, this is good description. Thanks Marijn! > Hope I'm not considered being too picky. I first sketch **how** the original > patch created a problem, then explain how this patch is intending to fix it, > and finally describe that we went a step further and ensured no other SoCs > are suffering from a similar problem. > > - Marijn > Its indeed a bug introduced due to msm_dp_desc_sc7180 re-use. There is no widebus on this chipset. With the commit text fixed like above, Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com> >> >> Fixes: c7c412202623 ("drm/msm/dp: enable widebus on all relevant chipsets") >> Signed-off-by: James A. MacInnes <james.a.macinnes@gmail.com> >> --- >> drivers/gpu/drm/msm/dp/dp_display.c | 7 ++++++- >> 1 file changed, 6 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c >> index aff51bb973eb..e30cccd63910 100644 >> --- a/drivers/gpu/drm/msm/dp/dp_display.c >> +++ b/drivers/gpu/drm/msm/dp/dp_display.c >> @@ -126,6 +126,11 @@ static const struct msm_dp_desc msm_dp_desc_sa8775p[] = { >> {} >> }; >> >> +static const struct msm_dp_desc msm_dp_desc_sdm845[] = { >> + { .io_start = 0x0ae90000, .id = MSM_DP_CONTROLLER_0 }, >> + {} >> +}; >> + >> static const struct msm_dp_desc msm_dp_desc_sc7180[] = { >> { .io_start = 0x0ae90000, .id = MSM_DP_CONTROLLER_0, .wide_bus_supported = true }, >> {} >> @@ -178,7 +183,7 @@ static const struct of_device_id msm_dp_dt_match[] = { >> { .compatible = "qcom,sc8180x-edp", .data = &msm_dp_desc_sc8180x }, >> { .compatible = "qcom,sc8280xp-dp", .data = &msm_dp_desc_sc8280xp }, >> { .compatible = "qcom,sc8280xp-edp", .data = &msm_dp_desc_sc8280xp }, >> - { .compatible = "qcom,sdm845-dp", .data = &msm_dp_desc_sc7180 }, >> + { .compatible = "qcom,sdm845-dp", .data = &msm_dp_desc_sdm845 }, >> { .compatible = "qcom,sm8350-dp", .data = &msm_dp_desc_sc7180 }, >> { .compatible = "qcom,sm8650-dp", .data = &msm_dp_desc_sm8650 }, >> { .compatible = "qcom,x1e80100-dp", .data = &msm_dp_desc_x1e80100 }, >> >> -- >> 2.43.0 >>
diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c index aff51bb973eb..e30cccd63910 100644 --- a/drivers/gpu/drm/msm/dp/dp_display.c +++ b/drivers/gpu/drm/msm/dp/dp_display.c @@ -126,6 +126,11 @@ static const struct msm_dp_desc msm_dp_desc_sa8775p[] = { {} }; +static const struct msm_dp_desc msm_dp_desc_sdm845[] = { + { .io_start = 0x0ae90000, .id = MSM_DP_CONTROLLER_0 }, + {} +}; + static const struct msm_dp_desc msm_dp_desc_sc7180[] = { { .io_start = 0x0ae90000, .id = MSM_DP_CONTROLLER_0, .wide_bus_supported = true }, {} @@ -178,7 +183,7 @@ static const struct of_device_id msm_dp_dt_match[] = { { .compatible = "qcom,sc8180x-edp", .data = &msm_dp_desc_sc8180x }, { .compatible = "qcom,sc8280xp-dp", .data = &msm_dp_desc_sc8280xp }, { .compatible = "qcom,sc8280xp-edp", .data = &msm_dp_desc_sc8280xp }, - { .compatible = "qcom,sdm845-dp", .data = &msm_dp_desc_sc7180 }, + { .compatible = "qcom,sdm845-dp", .data = &msm_dp_desc_sdm845 }, { .compatible = "qcom,sm8350-dp", .data = &msm_dp_desc_sc7180 }, { .compatible = "qcom,sm8650-dp", .data = &msm_dp_desc_sm8650 }, { .compatible = "qcom,x1e80100-dp", .data = &msm_dp_desc_x1e80100 },
SDM845 DPU hardware is rev 4.0.0 per hardware documents. Original patch to enable wide_bus operation did not take into account the SDM845 and it got carried over by accident. - Incorrect setting caused inoperable DisplayPort. - Corrected by separating SDM845 into its own descriptor. Fixes: c7c412202623 ("drm/msm/dp: enable widebus on all relevant chipsets") Signed-off-by: James A. MacInnes <james.a.macinnes@gmail.com> --- drivers/gpu/drm/msm/dp/dp_display.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)