linux-kernel - Re: [PATCH v8 1/4] drm/msm/dp: Add eDP support via aux

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Date:   Thu, 21 Apr 2022 08:23:05 -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>,
        "Aravind Venkateswaran (QUIC)" <quic_aravindh@...cinc.com>,
        Steev Klimaszewski <steev@...i.org>
Subject: Re: [PATCH v8 1/4] drm/msm/dp: Add eDP support via aux_bus

Hi,

On Thu, Apr 21, 2022 at 7:37 AM Sankeerth Billakanti
<quic_sbillaka@...cinc.com> wrote:
>
> @@ -1530,6 +1532,61 @@ void msm_dp_debugfs_init(struct msm_dp *dp_display, struct drm_minor *minor)
>         }
>  }
>
> +static int dp_display_get_next_bridge(struct msm_dp *dp)
> +{
> +       int rc;
> +       struct dp_display_private *dp_priv;
> +       struct device_node *aux_bus;
> +       struct device *dev;
> +
> +       dp_priv = container_of(dp, struct dp_display_private, dp_display);
> +       dev = &dp_priv->pdev->dev;
> +       aux_bus = of_get_child_by_name(dev->of_node, "aux-bus");
> +
> +       if (aux_bus && dp->is_edp) {
> +               dp_display_host_init(dp_priv);
> +               dp_catalog_ctrl_hpd_config(dp_priv->catalog);
> +               dp_display_host_phy_init(dp_priv);
> +               enable_irq(dp_priv->irq);
> +
> +               rc = devm_of_dp_aux_populate_ep_devices(dp_priv->aux);

I think a comment was requested above that line saying something like:

/*
 * The code below assumes that the panel will finish probing
 * by the time devm_of_dp_aux_populate_ep_devices() returns.
 * This isn't a great assumption since it will fail if the
 * panel driver is probed asynchronously but is the best we
 * can do without a bigger driver reorganization.
 */


> +               of_node_put(aux_bus);
> +               if (rc)
> +                       goto edp_error;
> +       } else if (dp->is_edp) {
> +               DRM_ERROR("eDP aux_bus not found\n");
> +               rc = -ENODEV;
> +               goto error;

This goto doesn't add much. Just leave the above like it was in v7.
return -ENODEV w/ no goto.


> +       }
> +
> +       /*
> +        * External bridges are mandatory for eDP interfaces: one has to
> +        * provide at least an eDP panel (which gets wrapped into panel-bridge).
> +        *
> +        * For DisplayPort interfaces external bridges are optional, so
> +        * silently ignore an error if one is not present (-ENODEV).
> +        */
> +       rc = dp_parser_find_next_bridge(dp_priv->parser);
> +       if (rc && dp->is_edp) {
> +               DRM_ERROR("eDP: cannot find the next bridge, rc = %d\n", rc);
> +               goto edp_error;
> +       } else if (rc && rc != -ENODEV) {
> +               DRM_ERROR("DP: cannot find the next bridge, rc = %d\n", rc);
> +               goto error;
> +       }

The above wouldn't be my favorite way of doing this. Instead, I would
have written:

  if (rc) {
    DRM_ERROR("Cannot find the next bridge, rc = %d\n", rc);
    goto err;
  }
  ...

err:
  if (dp->is_edp) {
    disable_irq(...);
    dp_display_host_phy_exit(...);
    dp_display_host_deinit(...);
  }
  return rc;

> +
> +       dp->next_bridge = dp_priv->parser->next_bridge;
> +
> +       return 0;
> +
> +edp_error:
> +       disable_irq(dp_priv->irq);
> +       dp_display_host_phy_exit(dp_priv);
> +       dp_display_host_deinit(dp_priv);
> +error:
> +       return rc;
> +}
> +
>  int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev,
>                         struct drm_encoder *encoder)
>  {

With the above fixes, I'd be happy enough for my Reviewed-by tag with
the expectation that continued work will happen to continue cleaning
this up.


-Doug