linux-kernel - Re: [PATCH] drm/bridge: ti-sn65dsi86: Associate DSI device lifetime with auxiliary device

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Date:   Thu, 12 Oct 2023 09:43:57 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev, dri-devel@...ts.freedesktop.org,
        Maxime Ripard <maxime@...no.tech>
Subject: Re: [PATCH] drm/bridge: ti-sn65dsi86: Associate DSI device lifetime
 with auxiliary device

Hi,

On Thu, Oct 5, 2023 at 10:18 AM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Doug Anderson (2023-10-02 17:31:41)
> > Hi,
> >
> > On Mon, Oct 2, 2023 at 4:54 PM Stephen Boyd <swboyd@...omium.org> wrote:
> > >
> > > The kernel produces a warning splat and the DSI device fails to register
> > > in this driver if the i2c driver probes, populates child auxiliary
> > > devices, and then somewhere in ti_sn_bridge_probe() a function call
> > > returns -EPROBE_DEFER. When the auxiliary driver probe defers, the dsi
> > > device created by devm_mipi_dsi_device_register_full() is left
> > > registered because the devm managed device used to manage the lifetime
> > > of the DSI device is the parent i2c device, not the auxiliary device
> > > that is being probed.
> > >
> > > Associate the DSI device created and managed by this driver to the
> > > lifetime of the auxiliary device, not the i2c device, so that the DSI
> > > device is removed when the auxiliary driver unbinds. Similarly change
> > > the device pointer used for dev_err_probe() so the deferred probe errors
> > > are associated with the auxiliary device instead of the parent i2c
> > > device so we can narrow down future problems faster.
> > >
> > > Cc: Douglas Anderson <dianders@...omium.org>
> > > Cc: Maxime Ripard <maxime@...no.tech>
> > > Fixes: c3b75d4734cb ("drm/bridge: sn65dsi86: Register and attach our DSI device at probe")
> >
> > Even before that commit I think it was using the main "dev" instead of
> > the auxiliary device's "dev" for some "devm" stuff. I guess the
> > difference is that it wouldn't mess with probe deferral? Searching
> > back, I think the first instance of a case that was using "devm_" with
> > the wrong device was commit 4e5763f03e10 ("drm/bridge: ti-sn65dsi86:
> > Wrap panel with panel-bridge")? Would it make sense to use that as a
> > Fixes, you think?
>
> The problem for me is that the dsi device is registered twice. That
> happens because probe for the auxiliary device happens twice. I was
> cautious about the fixes tag here because it didn't look like probe
> deferral was happening before commit c3b75d4734cb.
>
> >
> > In any case, this looks reasonable to me:
> >
> > Reviewed-by: Douglas Anderson <dianders@...omium.org>
> >
> > I'll give it a week and then apply to "-fixes" if everything is quiet.
>
> Thanks!

Pushed to drm-misc-fixes leaving your existing "Fixes" line:

7b821db95140 drm/bridge: ti-sn65dsi86: Associate DSI device lifetime
with auxiliary device

-Doug