linux-kernel - Re: [32/39] drm: renesas: shmobile: Shutdown the display on remove

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Date:   Wed, 5 Jul 2023 12:29:34 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Sui Jingfeng <suijingfeng@...ngson.cn>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Magnus Damm <magnus.damm@...il.com>,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [32/39] drm: renesas: shmobile: Shutdown the display on remove

Hi Sui,

On Tue, Jun 27, 2023 at 4:57 PM Sui Jingfeng <suijingfeng@...ngson.cn> wrote:
> On 2023/6/22 17:21, Geert Uytterhoeven wrote:
> > When the device is unbound from the driver, the display may be active.
> > Make sure it gets shut down.
>
> would you mind to give a short description why this is necessary.

That's a good comment.
It turned out that this is not really necessary here, but to avoid a regression
with "[PATCH 34/39] drm: renesas: shmobile: Atomic conversion part 1", where
it is needed to call drm_atomic_helper_shutdown().
As the comments for drm_atomic_helper_shutdown() says it is the
atomic version of drm_helper_force_disable_all(), I figured I had to
introduce a call to the latter first, before doing the atomic conversion.

Does that make sense?

> > Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> > Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>

> > --- a/drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c
> > +++ b/drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c
> > @@ -16,6 +16,7 @@
> >   #include <linux/pm_runtime.h>
> >   #include <linux/slab.h>
> >
> > +#include <drm/drm_crtc_helper.h>
> >   #include <drm/drm_drv.h>
> >   #include <drm/drm_fbdev_generic.h>
> >   #include <drm/drm_gem_dma_helper.h>
> > @@ -145,6 +146,7 @@ static int shmob_drm_remove(struct platform_device *pdev)
> >       struct drm_device *ddev = &sdev->ddev;
> >
> >       drm_dev_unregister(ddev);
> > +     drm_helper_force_disable_all(ddev);
>
> Is it that the DRM core recommend us to use
> drm_atomic_helper_disable_all() ?

Well, drm_atomic_helper_shutdown() is a convenience wrapper
around drm_atomic_helper_disable_all()... But we can't call any
atomic helpers yet, before the conversion to atomic modesetting.

>
> >       drm_kms_helper_poll_fini(ddev);
> >       return 0;
> >   }

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds