linux-kernel - Re: [PATCH v1 2/3] drm/msm/dp: decoupling dp->id out of dp controller_id at scxxxx_dp

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Date:   Fri, 24 Jun 2022 13:00:37 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>, agross@...nel.org,
        airlied@...ux.ie, bjorn.andersson@...aro.org, daniel@...ll.ch,
        dianders@...omium.org, dmitry.baryshkov@...aro.org,
        dri-devel@...ts.freedesktop.org, robdclark@...il.com,
        sean@...rly.run, vkoul@...nel.org
Cc:     quic_abhinavk@...cinc.com, quic_aravindh@...cinc.com,
        quic_sbillaka@...cinc.com, freedreno@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/3] drm/msm/dp: decoupling dp->id out of dp
 controller_id at scxxxx_dp_cfg table

Quoting Kuogee Hsieh (2022-06-24 10:15:11)
> Current the index (dp->id) of DP descriptor table (scxxxx_dp_cfg[]) are tightly
> coupled with DP controller_id. This means DP use controller id 0 must be placed
> at first entry of DP descriptor table (scxxxx_dp_cfg[]). Otherwise the internal
> INTF will mismatch controller_id. This will cause controller kickoff wrong
> interface timing engine and cause dpu_encoder_phys_vid_wait_for_commit_done
> vblank timeout error.
>
> This patch add controller_id field into struct msm_dp_desc to break the tightly
> coupled relationship between index (dp->id) of DP descriptor table with DP
> controller_id.

Please no. This reverts the intention of commit bb3de286d992
("drm/msm/dp: Support up to 3 DP controllers")

    A new enum is introduced to document the connection between the
    instances referenced in the dpu_intf_cfg array and the controllers in
    the DP driver and sc7180 is updated.

It sounds like the intent of that commit failed to make a strong enough
connection. Now it needs to match the INTF number as well? I can't
really figure out what is actually wrong, because this patch undoes that
intentional tight coupling. Is the next patch the important part that
flips the order of the two interfaces?