linux-kernel - Re: [PATCH] drm/radeon: Update pitch for page flip

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Message-ID: <CADnq5_PDtEn1y5HJBRHXw8o11LVwSRDKNtQgZtN5u0CW5ZspnQ@mail.gmail.com>
Date:   Mon, 2 Aug 2021 10:51:51 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Christian König <christian.koenig@....com>,
        Zhenneng Li <lizhenneng@...inos.cn>,
        Alex Deucher <alexander.deucher@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] drm/radeon: Update pitch for page flip

On Mon, Aug 2, 2021 at 4:31 AM Daniel Vetter <daniel@...ll.ch> wrote:
>
> On Mon, Aug 02, 2021 at 10:12:47AM +0200, Christian König wrote:
> > Am 02.08.21 um 09:43 schrieb Zhenneng Li:
> > > When primary bo is updated, crtc's pitch may
> > > have not been updated, this will lead to show
> > > disorder content when user changes display mode,
> > > we update crtc's pitch in page flip to avoid
> > > this bug.
> > > This refers to amdgpu's pageflip.
> >
> > Alex is the expert to ask about that code, but I'm not sure if that is
> > really correct for the old hardware.
> >
> > As far as I know the crtc's pitch should not change during a page flip, but
> > only during a full mode set.
> >
> > So could you elaborate a bit more how you trigger this?
>
> legacy page_flip ioctl only verifies that the fb->format stays the same.
> It doesn't check anything else (afair never has), this is all up to
> drivers to verify.
>
> Personally I'd say add a check to reject this, since testing this and
> making sure it really works everywhere is probably a bit much on this old
> hw.

If just the pitch changed, that probably wouldn't be much of a
problem, but if the pitch is changing, that probably implies other
stuff has changed as well and we'll just be chasing changes.  I agree
it would be best to just reject anything other than updating the
scanout address.

Alex

> -Daniel
>
> >
> > Thanks,
> > Christian.
> >
> > >
> > > Cc: Alex Deucher <alexander.deucher@....com>
> > > Cc: "Christian König" <christian.koenig@....com>
> > > Cc: "Pan, Xinhui" <Xinhui.Pan@....com>
> > > Cc: David Airlie <airlied@...ux.ie>
> > > Cc: Daniel Vetter <daniel@...ll.ch>
> > > Cc: amd-gfx@...ts.freedesktop.org
> > > Cc: dri-devel@...ts.freedesktop.org
> > > Cc: linux-kernel@...r.kernel.org
> > > Signed-off-by: Zhenneng Li <lizhenneng@...inos.cn>
> > > ---
> > >   drivers/gpu/drm/radeon/evergreen.c | 8 +++++++-
> > >   1 file changed, 7 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
> > > index 36a888e1b179..eeb590d2dec2 100644
> > > --- a/drivers/gpu/drm/radeon/evergreen.c
> > > +++ b/drivers/gpu/drm/radeon/evergreen.c
> > > @@ -28,6 +28,7 @@
> > >   #include <drm/drm_vblank.h>
> > >   #include <drm/radeon_drm.h>
> > > +#include <drm/drm_fourcc.h>
> > >   #include "atom.h"
> > >   #include "avivod.h"
> > > @@ -1414,10 +1415,15 @@ void evergreen_page_flip(struct radeon_device *rdev, int crtc_id, u64 crtc_base,
> > >                      bool async)
> > >   {
> > >     struct radeon_crtc *radeon_crtc = rdev->mode_info.crtcs[crtc_id];
> > > +   struct drm_framebuffer *fb = radeon_crtc->base.primary->fb;
> > > -   /* update the scanout addresses */
> > > +   /* flip at hsync for async, default is vsync */
> > >     WREG32(EVERGREEN_GRPH_FLIP_CONTROL + radeon_crtc->crtc_offset,
> > >            async ? EVERGREEN_GRPH_SURFACE_UPDATE_H_RETRACE_EN : 0);
> > > +   /* update pitch */
> > > +   WREG32(EVERGREEN_GRPH_PITCH + radeon_crtc->crtc_offset,
> > > +          fb->pitches[0] / fb->format->cpp[0]);
> > > +   /* update the scanout addresses */
> > >     WREG32(EVERGREEN_GRPH_PRIMARY_SURFACE_ADDRESS_HIGH + radeon_crtc->crtc_offset,
> > >            upper_32_bits(crtc_base));
> > >     WREG32(EVERGREEN_GRPH_PRIMARY_SURFACE_ADDRESS + radeon_crtc->crtc_offset,
> > >
> > > No virus found
> > >             Checked by Hillstone Network AntiVirus
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch