Hi, [removed previous conversation] > > Hi Dmitry and Abhinav, > > Just wanted to follow up on this thread. I've gone over the MSM-specific > DSC params for DP and DSI and have found a few shared calculations and > variables between both DSI and DP paths: > > - (as mentioned earlier in the thread) almost all the calculations in > dpu_dsc_populate_dsc_config() match dsi_populate_dsc_params() [1]. The > only difference in the math I'm seeing is initial_scale_value. The value in dsi code is valid for initial_offset = 6144. Please use the formula from the standard (= sde_dsc_populate_dsc_config) and add it to drm_dsc_helper.c If I remember correctly the last remaining item in dsi_populate_dsc_params() (except mentioned initial_offset) was line_buf_depth, see [3]. I'm not sure about setting it to bpc+1. According to the standard it should come from a DSC decoder spec, which means it should be set by the DSI panel driver or via drm_dp_dsc_sink_line_buf_depth() in the case of DP output. > - dsc_extra_pclk_cycle_cnt and dce_bytes_per_line, which were introduced > in Kuogee's v1 DSC series [2], are used for DSI, DP, and the DPU timing > engine. dsc_extra_pclk_cycle_cnt is calculated based on pclk_per_line > (which is calculated differently between DP and DSI), but > dce_bytes_per_line is calculated the same way between DP and DSI. > > To avoid having to duplicate math in 2 different places, I think it > would help to have these calculations in some msm_dsc_helper.c file. Any > thoughts on this? dsc_extra_pclk_cycle_cnt and dce_bytes_per_line are used only in DPU code, so they can stay in DPU driver. > > Thanks, > > Jessica Zhang > > [1] > https://elixir.bootlin.com/linux/v6.3-rc2/source/drivers/gpu/drm/msm/dsi/dsi_host.c#L1756 > > [2] https://patchwork.freedesktop.org/patch/519845/?series=113240&rev=1 [3] https://patchwork.freedesktop.org/patch/525441/?series=114472&rev=2 -- With best wishes Dmitry
