Re: [Intel-gfx] [PATCH] drm/i915/display: assume some pixelrate for src smaller than 1

[Drew Davenport <ddavenport@chromium.org>]

On Wed, Jan 11, 2023 at 04:19:00PM +0200, Ville Syrjälä wrote:
> On Wed, Jan 04, 2023 at 02:44:48PM +0200, Juha-Pekka Heikkila wrote:
> > intel_adjusted_rate() didn't take into account src rectangle
> > can be less than 1 in width or height.
> 
> This should not get called in those cases. What does the
> backtrace look like?

In my repro of this issue, the backtrace looks as follows:

[  180.798331] RIP: 0010:intel_plane_pixel_rate+0x4a/0x53
[  180.798336] Code: <snip long line>
[  180.798338] RSP: 0018:ffffb080ce4179b8 EFLAGS: 00010246
[  180.798341] RAX: ffffffffffffffff RBX: ffff98cd22a24000 RCX: 0000000000000a00
[  180.798343] RDX: 0000000000000000 RSI: ffff98cccbae7000 RDI: 0000000000000000
[  180.798346] RBP: ffffb080ce4179b8 R08: 0000000000087780 R09: 0000000000000002
[  180.798348] R10: 0000000000000a00 R11: 0000000000000000 R12: 0000000000000000
[  180.798350] R13: ffff98cd0e495400 R14: ffff98ccc34e0000 R15: ffff98cccbae7000
[  180.798352] FS:  00007b84119b5000(0000) GS:ffff98d02f900000(0000) knlGS:0000000000000000
[  180.798354] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  180.798357] CR2: 00007ffc2d5e4080 CR3: 00000001042ee006 CR4: 0000000000770ee0
[  180.798359] PKRU: 55555554
[  180.798361] Call Trace:
[  180.798364]  <TASK>
[  180.798366]  intel_plane_atomic_check_with_state+0x1fd/0x6ea
[  180.798370]  ? intel_plane_atomic_check+0x11b/0x145
[  180.798373]  intel_atomic_check_planes+0x263/0x7ce
[  180.798376]  ? drm_atomic_helper_check_modeset+0x189/0x923
[  180.798380]  intel_atomic_check+0x14e4/0x184d
[  180.798382]  ? intel_rps_mark_interactive+0x23/0x6a
[  180.798386]  drm_atomic_check_only+0x3ec/0x98f
[  180.798391]  drm_atomic_commit+0xa2/0x105
[  180.798394]  ? drm_atomic_set_fb_for_plane+0x96/0xa5
[  180.798397]  drm_atomic_helper_update_plane+0xdc/0x11f
[  180.798400]  drm_mode_setplane+0x236/0x30c
[  180.798404]  ? drm_any_plane_has_format+0x51/0x51
[  180.798407]  drm_ioctl_kernel+0xda/0x14d
[  180.798411]  drm_ioctl+0x27e/0x3b4
[  180.798414]  ? drm_any_plane_has_format+0x51/0x51
[  180.798418]  __se_sys_ioctl+0x7a/0xbc
[  180.798421]  do_syscall_64+0x55/0x9d
[  180.798424]  ? exit_to_user_mode_prepare+0x3c/0x8b
[  180.798427]  entry_SYSCALL_64_after_hwframe+0x61/0xcb

If this function shouldn't be called in such a case, then perhaps
I should revist my original attempt at fixing this in
https://patchwork.freedesktop.org/patch/516060 by rejecting such a
configuration?

I'll respond to Alan on that thread.

> 
> > 
> > Signed-off-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_atomic_plane.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_atomic_plane.c b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> > index 10e1fc9d0698..a9948e8d3543 100644
> > --- a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> > +++ b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> > @@ -144,7 +144,7 @@ unsigned int intel_adjusted_rate(const struct drm_rect *src,
> >  				 const struct drm_rect *dst,
> >  				 unsigned int rate)
> >  {
> > -	unsigned int src_w, src_h, dst_w, dst_h;
> > +	unsigned int src_w, src_h, dst_w, dst_h, dst_wh;
> >  
> >  	src_w = drm_rect_width(src) >> 16;
> >  	src_h = drm_rect_height(src) >> 16;
> > @@ -155,8 +155,10 @@ unsigned int intel_adjusted_rate(const struct drm_rect *src,
> >  	dst_w = min(src_w, dst_w);
> >  	dst_h = min(src_h, dst_h);
> >  
> > -	return DIV_ROUND_UP_ULL(mul_u32_u32(rate, src_w * src_h),
> > -				dst_w * dst_h);
> > +	/* in case src contained only fractional part */
> > +	dst_wh = max(dst_w * dst_h, (unsigned) 1);
> > +
> > +	return DIV_ROUND_UP_ULL(mul_u32_u32(rate, src_w * src_h), dst_wh);
> >  }
> >  
> >  unsigned int intel_plane_pixel_rate(const struct intel_crtc_state *crtc_state,
> > -- 
> > 2.37.3
> 
> -- 
> Ville Syrjälä
> Intel