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 > > 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
