linux-kernel - Re: [PATCH v2] drm/bridge: sn65dsi86: defer if there is no dsi host

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Message-ID: <CAD=FV=VSRB45vFJZhVg7OTy2ZAv6UZ638YjQQiZemt9-AD1JXw@mail.gmail.com>
Date:   Tue, 7 Dec 2021 13:42:36 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Rob Clark <robdclark@...il.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Maxime Ripard <maxime@...no.tech>,
        Stephen Boyd <swboyd@...omium.org>,
        Jernej Škrabec <jernej.skrabec@...il.com>,
        Rob Clark <robdclark@...omium.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Sam Ravnborg <sam@...nborg.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/bridge: sn65dsi86: defer if there is no dsi host

Hi,

On Tue, Dec 7, 2021 at 1:33 PM Rob Clark <robdclark@...il.com> wrote:
>
> From: Rob Clark <robdclark@...omium.org>
>
> Otherwise we don't get another shot at it if the bridge probes before
> the dsi host is registered.  It seems like this is what *most* (but not
> all) of the other bridges do.
>
> It looks like this was missed in the conversion to attach dsi host at
> probe time.
>
> Fixes: c3b75d4734cb ("drm/bridge: sn65dsi86: Register and attach our DSI device at probe")
> Signed-off-by: Rob Clark <robdclark@...omium.org>
> ---
> v2: Drop DRM_ERROR() in favor of drm_err_probe() and shift around the
>     spot where we report the error
>
>  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> index 02b490671f8f..8f1321ca819e 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> @@ -714,10 +714,8 @@ static int ti_sn_attach_host(struct ti_sn65dsi86 *pdata)
>         };
>
>         host = of_find_mipi_dsi_host_by_node(pdata->host_node);
> -       if (!host) {
> -               DRM_ERROR("failed to find dsi host\n");
> -               return -ENODEV;
> -       }
> +       if (!host)
> +               return -EPROBE_DEFER;
>
>         dsi = devm_mipi_dsi_device_register_full(dev, host, &info);
>         if (IS_ERR(dsi)) {
> @@ -1267,8 +1265,10 @@ static int ti_sn_bridge_probe(struct auxiliary_device *adev,
>         drm_bridge_add(&pdata->bridge);
>
>         ret = ti_sn_attach_host(pdata);
> -       if (ret)
> +       if (ret) {
> +               dev_err_probe(pdata->dev, ret, "failed to attach dsi host");

nit: Needs a "\n" at the end, doesn't it?


>                 goto err_remove_bridge;
> +       }

It's going to be a little funny now because if the
devm_mipi_dsi_attach() call fails you'll report "failed to attach dsi
host" twice (once using DRM_ERROR in ti_sn_attach_host() and once
here). Probably all the error messages could be removed from
ti_sn_attach_host() and you could rely on this new one because:
* devm_mipi_dsi_device_register_full() already appears plenty chatty.
* this is the same message that devm_mipi_dsi_attach() was printing out anyway.

In any case, it's not really a big deal, so with the "\n" added I'm
happy with my Reviewed-by.

I'm happy to apply this to to drm-misc-next tomorrow if there are no
objections. I can always add the "\n" myself unless you want to send a
v3 with it and/or want to remove more error messages. ;-)

-Doug