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 16:12:48 -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 15:53:45)
>
> MSM_DP_CONTROLLER_1 need to match to the index = 1 of sc7280_dp_cfg[] <== This is correct
>
> The problem is sc7280_dp_cfg[] have two entries since eDP place at index
> of MSM_DP_CONTROLLER_1.
>
> but .num_desc = 1  <== this said only have one entry at sc7280_dp_cfg[]
> table. Therefore eDP will never be found at for loop  at
> _dpu_kms_initialize_displayport().
>

Yes, but what else does the MSM_DP_CONTROLLER_1 need to match? Because
the intention of the previous commit was to make it so the order of
sc7280_dp_cfg couldn't be messed up and not match the
MSM_DP_CONTROLLER_1 value that lives in sc7280_intf[].

>
> Sorry, my mistake. it is not in drm_bridge_add.
>
> It should be in dpu_encoder_init() of _dpu_kms_initialize_displayport().
>
> can you make below changes (patch) to _dpu_kms_initialize_displayport().
>

Yes, I've made that change to try to understand the problem. I still
don't understand, sadly. Does flipping the order of iteration through
'priv->dp' somehow mean that the crtc that is assigned to the eDP
connector is left unchanged? Whereas without registering the eDP encoder
first means we have to change the crtc for the eDP encoder and that
can't be done atomically?