linux-kernel - Re: [RFT PATCH 15/15] drm/renesas/shmobile: Call drm_helper_force_disable

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Message-ID: <CAD=FV=WufC0WrnEZVEi5vQudpGnxiphJpJ6SwsEitm8zEnzJiA@mail.gmail.com>
Date:   Tue, 5 Sep 2023 14:10:55 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     dri-devel@...ts.freedesktop.org,
        Maxime Ripard <mripard@...nel.org>, airlied@...il.com,
        biju.das.jz@...renesas.com, daniel@...ll.ch,
        kieran.bingham+renesas@...asonboard.com,
        laurent.pinchart@...asonboard.com, linux-kernel@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, paul@...pouillou.net,
        tzimmermann@...e.de
Subject: Re: [RFT PATCH 15/15] drm/renesas/shmobile: Call drm_helper_force_disable_all()
 at shutdown/remove time

Hi,

On Mon, Sep 4, 2023 at 12:28 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Douglas,
>
> On Sat, Sep 2, 2023 at 1:42 AM Douglas Anderson <dianders@...omium.org> wrote:
> > Based on grepping through the source code, this driver appears to be
> > missing a call to drm_atomic_helper_shutdown(), or in this case the
> > non-atomic equivalent drm_helper_force_disable_all(), at system
> > shutdown time and at driver remove time. This is important because
> > drm_helper_force_disable_all() will cause panels to get disabled
> > cleanly which may be important for their power sequencing. Future
> > changes will remove any custom powering off in individual panel
> > drivers so the DRM drivers need to start getting this right.
> >
> > The fact that we should call drm_atomic_helper_shutdown(), or in this
> > case the non-atomic equivalent drm_helper_force_disable_all(), in the
> > case of OS shutdown/restart comes straight out of the kernel doc
> > "driver instance overview" in drm_drv.c.
> >
> > Suggested-by: Maxime Ripard <mripard@...nel.org>
> > Signed-off-by: Douglas Anderson <dianders@...omium.org>
>
> Thanks for your patch!
>
> > --- a/drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c
> > +++ b/drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c
> > @@ -179,12 +180,20 @@ static int shmob_drm_remove(struct platform_device *pdev)
> >
> >         drm_dev_unregister(ddev);
> >         drm_kms_helper_poll_fini(ddev);
> > +       drm_helper_force_disable_all(ddev);
>
> After "[PATCH v3 36/41] drm: renesas: shmobile: Atomic conversion part
> 1"[1], this function will already call drm_atomic_helper_shutdown()...
>
> >         free_irq(sdev->irq, ddev);
> >         drm_dev_put(ddev);
> >
> >         return 0;
> >  }
> >
> > +static void shmob_drm_shutdown(struct platform_device *pdev)
> > +{
> > +       struct shmob_drm_device *sdev = platform_get_drvdata(pdev);
> > +
> > +       drm_helper_force_disable_all(sdev->ddev);
>
> ... and this should be replaced by a call to drm_atomic_helper_shutdown().
>
> [1] https://lore.kernel.org/dri-devel/fd7a6702490bd431f314d6591551bb39e77e3304.1692178020.git.geert+renesas@glider.be

Ah, thanks! I will put this patch on hold and check back in a few
weeks to see how things are looking. If you wanted to fold it into
your series I certainly wouldn't object to it, but if not that's fine
too. ;-)

-Doug