[Intel-gfx] [PATCH 1/2] drm/i915/skl: Allow universal planes to position

[Ville Syrjälä]

On Tue, Oct 06, 2015 at 07:29:54AM -0700, Matt Roper wrote:
> On Tue, Oct 06, 2015 at 02:32:47PM +0100, Tvrtko Ursulin wrote:
> > 
> > On 10/04/15 10:07, Sonika Jindal wrote:
> > >Signed-off-by: Sonika Jindal <sonika.jindal at intel.com>
> > >Reviewed-by: Matt Roper <matthew.d.roper at intel.com>
> > >---
> > >  drivers/gpu/drm/i915/intel_display.c |    7 ++++++-
> > >  1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > >diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > >index ceb2e61..f0bbc22 100644
> > >--- a/drivers/gpu/drm/i915/intel_display.c
> > >+++ b/drivers/gpu/drm/i915/intel_display.c
> > >@@ -12150,16 +12150,21 @@ intel_check_primary_plane(struct drm_plane *plane,
> > >  	struct drm_rect *dest = &state->dst;
> > >  	struct drm_rect *src = &state->src;
> > >  	const struct drm_rect *clip = &state->clip;
> > >+	bool can_position = false;
> > >  	int ret;
> > >
> > >  	crtc = crtc ? crtc : plane->crtc;
> > >  	intel_crtc = to_intel_crtc(crtc);
> > >
> > >+	if (INTEL_INFO(dev)->gen >= 9)
> > >+		can_position = true;
> > >+
> > >  	ret = drm_plane_helper_check_update(plane, crtc, fb,
> > >  					    src, dest, clip,
> > >  					    DRM_PLANE_HELPER_NO_SCALING,
> > >  					    DRM_PLANE_HELPER_NO_SCALING,
> > >-					    false, true, &state->visible);
> > >+					    can_position, true,
> > >+					    &state->visible);
> > >  	if (ret)
> > >  		return ret;
> > >
> > >
> > 
> > I have discovered today that, while this allows SetCrtc and SetPlane
> > ioctls to work with frame buffers which do not cover the plane, page
> > flips are not that lucky and fail roughly with:
> > 
> > [drm:drm_crtc_check_viewport] Invalid fb size 1080x1080 for CRTC
> > viewport 1920x1080+0+0.
> 
> Maybe I'm misunderstanding your explanation, but a framebuffer is always
> required to fill/cover the plane scanning out of it.  What this patch is
> supposed to be allowing is for the primary plane to not cover the entire
> CRTC (since that's something that only became possible for Intel
> hardware on the gen9+ platforms).  I.e., the primary plane is now
> allowed to positioned and resized to cover a subset of the CRTC area,
> just like "sprite" planes have always been able to.
> 
> If you've got a 1080x1080 framebuffer, then it's legal to have a
> 1080x1080 primary plane while running in 1920x1080 mode on SKL/BXT.
> However it is not legal to size the primary plane as 1920x1080 and use
> this same 1080x1080 framebuffer with any of our interfaces (setplane,
> setcrtc, pageflip, or atomic).
> 
> Are you using ioctls/libdrm directly or are you using igt_kms helpers?
> IIRC, the IGT helpers will try to be extra helpful and automatically
> size the plane to match the framebuffer (unless you override that
> behavior), so that might be what's causing the confusion here.

The problem is clear as day in drm_mode_page_flip_ioctl():
ret = drm_crtc_check_viewport(crtc, crtc->x, crtc->y, &crtc->mode, fb);
if (ret)
	goto out;

The fix should be easy; just extract the current src coordinates from
the plane state and check those against the new fb size. And then hope
that the plane state is really up to date.

And I'm sure rotated cases will go boom in some other ways. Probably
we should just switch over to using the full plane update for mmio
flips to fix it.

> 
> 
> Matt
> 
> > 
> > I have posted a quick IGT exerciser for this as "kms_rotation_crc:
> > Excercise page flips with 90 degree rotation". May not be that great
> > but shows the failure.
> > 
> > I am not that hot on meddling with this code, nor do I feel
> > competent to even try on my own at least. :/ Maybe just because the
> > atomic and plane related rewrites have been going on for so long,
> > and have multiple people involved, it all sounds pretty scary and
> > fragile.
> > 
> > But I think some sort of plan on how to fix this could be in order?
> > 
> > Regards,
> > 
> > Tvrtko
> 
> -- 
> Matt Roper
> Graphics Software Engineer
> IoTG Platform Enabling & Development
> Intel Corporation
> (916) 356-2795

-- 
Ville Syrjälä
Intel OTC