MIME-Version: 1.0
References: <1677267647-28672-1-git-send-email-quic_khsieh@quicinc.com>
 <1677267647-28672-2-git-send-email-quic_khsieh@quicinc.com>
 <42b3c193-8897-cfe9-1cae-2f9a66f7983a@linaro.org> <741be2a3-0208-2f40-eedf-d439c4e6795b@quicinc.com>
 <F8A4FC18-C64E-4011-BC08-18EB3B95A357@linaro.org> <d5ee8233-66c8-9b88-417c-6cf9cc5c84fe@quicinc.com>
 <CAA8EJpro5Q-2ZpnDJt40UhFX7Zp9oBhrto=FDOERzCDR2BDPvQ@mail.gmail.com>
 <f0dfba42-4674-3748-bf5d-39f6e1745f67@quicinc.com> <f1a6ee82-9502-7ea5-fe48-f296fc7df497@linaro.org>
 <3e114c0f-a042-6801-69bf-67436cb2a448@quicinc.com> <113a10b6-6097-c80e-c29c-6f61b2b2896a@linaro.org>
 <c4c0ebf8-275d-500f-4019-e3d7517a884f@quicinc.com> <CAA8EJppxX4haZSwdvVbN7bc6kXAyNO1rg6zWZv9wPFdqGrcXuw@mail.gmail.com>
 <c650e746-64c5-ce6b-933d-057349356b78@quicinc.com> <58E03B71-20C4-4F81-96C1-6D8CE517F3FB@linaro.org>
 <fd876ad2-3fd0-eaab-3407-dd32d494f662@quicinc.com> <a5d1a74f-1b7a-569d-e487-774720dfae22@quicinc.com>
In-Reply-To: <a5d1a74f-1b7a-569d-e487-774720dfae22@quicinc.com>
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date:   Thu, 16 Mar 2023 18:03:33 +0200
Message-ID: <CAA8EJpq_mwUt0+1yGYo6hRx8Vz12DumVdpEjJbPk8gGHhGZ2bA@mail.gmail.com>
Subject: Re: [Freedreno] [RFC PATCH 1/2] drm/msm/dpu: add dsc helper functions
To:     Jessica Zhang <quic_jesszhan@quicinc.com>
Cc:     Abhinav Kumar <quic_abhinavk@quicinc.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        quic_sbillaka@quicinc.com, sean@poorly.run, andersson@kernel.org,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        dianders@chromium.org, vkoul@kernel.org, agross@kernel.org,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        marijn.suijten@somainline.org, swboyd@chromium.org,
        Kuogee Hsieh <quic_khsieh@quicinc.com>,
        freedreno@lists.freedesktop.org,
        Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
        linux-arm-msm@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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