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

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Date:   Mon, 2 Aug 2021 10:31:24 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Christian König <christian.koenig@....com>
Cc:     Zhenneng Li <lizhenneng@...inos.cn>,
        Alex Deucher <alexander.deucher@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/radeon: Update pitch for page flip

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.
-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