Messages in this thread | | | Date | Thu, 16 Mar 2023 09:13:29 -0700 | Subject | Re: [Freedreno] [RFC PATCH 1/2] drm/msm/dpu: add dsc helper functions | From | Abhinav Kumar <> |
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On 3/16/2023 9:03 AM, Dmitry Baryshkov wrote: > 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. >
They can stay in the dpu driver is fine but where?
Like Jessica wrote, this is computed and used in 3 places today :
1) DSI video engine computation 2) DP controller computation 3) timing engine programming
So either we have a helper in a common location somewhere so that these 3 modules can call that helper and use it OR each module duplicates the computation code.
What should be the common location is the discussion here.
It cannot be dpu_encoder.c as the DSI/DP dont call into the encoder methods.
>> >> 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 > > >
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