Messages in this thread | | | Date | Thu, 13 Oct 2022 09:02:44 -0700 | Subject | Re: [Freedreno] [PATCH v3 06/10] drm/msm/dsi: Migrate to drm_dsc_compute_rc_parameters() | From | Abhinav Kumar <> |
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On 10/13/2022 2:36 AM, Marijn Suijten wrote: > On 2022-10-12 16:03:06, Abhinav Kumar wrote: >> >> >> On 10/9/2022 11:50 AM, Marijn Suijten wrote: >>> As per the FIXME this code is entirely duplicate with what is already >>> provided inside drm_dsc_compute_rc_parameters(), and it is yet unknown >>> why this comment was put in place instead of resolved from the get-go. >>> Not only does it save on duplication, it would have also spared certain >>> issues. >>> >>> For example, this code from downstream assumed dsc->bits_per_pixel to >>> contain an integer value, whereas the upstream drm_dsc_config struct has >>> it with 4 fractional bits. drm_dsc_compute_rc_parameters() already >>> accounts for this feat, and the sole remaining use of >>> dsc->bits_per_pixel inside dsi_populate_dsc_params() will be addressed >>> in a separate patch. >>> >> >> This is a nice cleanup! Thanks for doing this. I would actually like to >> move towards the drm_dsc_compute_rc_parameters() API. >> >> But I would like to hold back this change till Vinod clarifies because >> Vinod had mentioned that with drm_dsc_compute_rc_parameters() he was >> seeing a mismatch in the computation of two values. >> >> slice_bpg_offset and the final_offset. > > Unsurprisingly so because final_offset, and slice_bpg_offset through > initial_offset depend directly on bits_per_pixel. The main takeaway of > this series is that Vinod was interpreting this field as integer instead > of containing 4 fractional bits. If he updates his the panel driver [1] > to set bits_per_pixel = 8 << 4 instead of just 8 to account for this, > the values should check out once again. > > [1]: https://git.linaro.org/people/vinod.koul/kernel.git/commit/?h=topic/pixel3_5.18-rc1&id=1d7d98ad564f1ec69e7525e07418918d90f247a1 > > Once Vinod (or someone else in the posession of a Pixel 3) confirms > this, I can respin this series and more explicitly explain why the FIXME > was put in place, instead of being resolved outright? > > - Marijn
Makes perfect sense to me.
Will just wait for Vinod's tested-by.
> >> >> The difference between the upstream drm_dsc_compute_rc_parameters() and >> dsi_populate_dsc_params() causing this was not clear to me from his >> explanation earlier. >> >> So this was left as a to-do item. >> >> I would like this to be re-tested on pixel3 and check if this works for >> vinod. If not, i think its the right time to debug why and not delay >> this more. >> >> Thanks >> >> Abhinav
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