linux-kernel - Re: [PATCH v6 1/8] drm/msm/dp: Add eDP support via aux

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Message-ID: <CAD=FV=X+QvjwoT2zGP82KW4kD0oMUY6ZgCizSikNX_Uj8dNDqA@mail.gmail.com>
Date:   Thu, 31 Mar 2022 16:22:00 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Sankeerth Billakanti <quic_sbillaka@...cinc.com>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Rob Clark <robdclark@...il.com>,
        Sean Paul <seanpaul@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        quic_kalyant <quic_kalyant@...cinc.com>,
        "Abhinav Kumar (QUIC)" <quic_abhinavk@...cinc.com>,
        "Kuogee Hsieh (QUIC)" <quic_khsieh@...cinc.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        quic_vproddut <quic_vproddut@...cinc.com>,
        quic_aravindh@...cinc.com
Subject: Re: [PATCH v6 1/8] drm/msm/dp: Add eDP support via aux_bus

Hi,

On Wed, Mar 30, 2022 at 9:03 AM Sankeerth Billakanti
<quic_sbillaka@...cinc.com> wrote:
>
> @@ -1547,6 +1593,10 @@ int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev,
>
>         dp_display->encoder = encoder;
>
> +       ret = dp_display_get_next_bridge(dp_display);
> +       if (ret)
> +               return ret;

It feels weird to me that this is in a function called "modeset_init",
though I certainly don't know the structure of the MSM display code
well enough to fully comment. My expectation would have been that
devm_of_dp_aux_populate_ep_devices() would have been called from your
probe routine and then you would have returned -EPROBE_DEFER from your
probe if you were unable to find the panel afterwards.

Huh, but I guess you _are_ getting called (indirectly) from
dpu_kms_hw_init() and I can't imagine AUX transfers working before
that function is called, so maybe I should just accept that it's
complicated and let those who understand this driver better confirm
that it's OK. ;-)

> @@ -140,5 +140,6 @@ struct dp_parser {
>   * can be parsed using this module.
>   */
>  struct dp_parser *dp_parser_get(struct platform_device *pdev);
> +int dp_parser_find_next_bridge(struct dp_parser *parser);

Everything else in this file is described w/ kerneldoc. Shouldn't your
function also have a kerneldoc comment?