linux-kernel - Re: [RFT PATCH 01/15] drm/armada: Call drm_atomic_helper

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Message-ID: <CAD=FV=WT4Hf1XVA641WtNFg4WRYFKarU1WOkLPEbr0eiVQuZPg@mail.gmail.com>
Date:   Tue, 5 Sep 2023 07:23:54 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     dri-devel@...ts.freedesktop.org,
        Maxime Ripard <mripard@...nel.org>, airlied@...il.com,
        daniel@...ll.ch, linux-kernel@...r.kernel.org
Subject: Re: [RFT PATCH 01/15] drm/armada: Call drm_atomic_helper_shutdown()
 at shutdown time

Hi,

On Sun, Sep 3, 2023 at 8:53 AM Russell King (Oracle)
<linux@...linux.org.uk> wrote:
>
> On Fri, Sep 01, 2023 at 04:41:12PM -0700, Douglas Anderson wrote:
> > Based on grepping through the source code this driver appears to be
> > missing a call to drm_atomic_helper_shutdown() at system shutdown
> > time. Among other things, this means that if a panel is in use that it
> > won't be cleanly powered off at system shutdown time.
> >
> > The fact that we should call drm_atomic_helper_shutdown() in the case
> > of OS shutdown/restart comes straight out of the kernel doc "driver
> > instance overview" in drm_drv.c.
> >
> > This driver was fairly easy to update. The drm_device is stored in the
> > drvdata so we just have to make sure the drvdata is NULL whenever the
> > device is not bound.
>
> ... and there I think you have a misunderstanding of the driver model.
> Please have a look at device_unbind_cleanup() which will be called if
> probe fails, or when the device is removed (in other words, when it is
> not bound to a driver.)

...and there I think you didn't read this patch closely enough and
perhaps that you have a misunderstanding of the component model.
Please have a look at the difference between armada_drm_unbind() and
armada_drm_remove() and also check which of those two functions is
being modified by my patch. Were this patch adding a call to
"dev_set_drvdata(dev, NULL)" in armada_drm_remove() then your NAK
would be justified. However, I am not aware of anything in the
component unbind path nor in the failure case of component bind that
would NULL the drvdata.

Kindly look at the patch a second time with this in mind.

-Doug