[Intel-gfx] [PATCH] drm: atomic: fix legacy gamma set helper

[Daniel Vetter]

On Tue, Apr 12, 2016 at 01:51:02PM +0100, Lionel Landwerlin wrote:
> On 12/04/16 12:57, Daniel Vetter wrote:
> >On Mon, Apr 11, 2016 at 02:43:39PM +0100, Lionel Landwerlin wrote:
> >>Color management properties are a bit of an odd use case because
> >>they're not marked as atomic properties. Currently we're not updating
> >>the non atomic values so the drm_crtc_state is out of sync with the
> >>values stored in the crtc object.
> >tbh sounds like this is the bug here - why does the lookup of the correct
> >values stored in the crtc_state drm_atomic_crtc_get_property() not work?
> 
> This is only a problem when the kernel space modifies property values.
> User space ioctls do the right thing and update both places :
> 
> https://cgit.freedesktop.org/drm-intel/tree/drivers/gpu/drm/drm_crtc.c#n4916

Nah, the problem is that we check fro DRIVER_ATOMIC in
drm_atomic_get_property, and because i915 is still not fully atomic that
gives us the wrong answer.

Can you pls double-check that enabling i915 atomic (i915.nuclear_flip=1)
also fixes the bug?

i915 is the only driver still transitioning, I definitely don't want to
have hacks all over for it.

> >Duct-taping over this bug in every place we update these properties
> >(you're just patching one of many) won't scale.
> >
> >Also: Where's the igt for this failure?
> >-Daniel
> 
> There is : https://cgit.freedesktop.org/xorg/app/intel-gpu-tools/tree/tests/kms_pipe_color.c#n554
> That's how we caught it.

Needs a Testcase: igt/kms_pipe_color/$name line in the commit message. How
a bug was discovered and tested is a crucial part of a complete commit
message.
-Daniel

> 
> 
> >>v2: Update non atomic values only if commit succeeds (Bob Paauwe)
> >>
> >>v3: Do not access crtc_state after commit, use crtc->state (Maarten
> >>     Lankhorst)
> >>
> >>Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> >>Cc: Bob Paauwe <bob.j.paauwe at intel.com>
> >>Cc: <dri-devel at lists.freedesktop.org>
> >>Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
> >>---
> >>  drivers/gpu/drm/drm_atomic_helper.c | 8 ++++++++
> >>  1 file changed, 8 insertions(+)
> >>
> >>diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> >>index 7bf678e..13b86cf 100644
> >>--- a/drivers/gpu/drm/drm_atomic_helper.c
> >>+++ b/drivers/gpu/drm/drm_atomic_helper.c
> >>@@ -2979,6 +2979,14 @@ retry:
> >>  	if (ret)
> >>  		goto fail;
> >>+	drm_object_property_set_value(&crtc->base,
> >>+			config->degamma_lut_property, 0);
> >>+	drm_object_property_set_value(&crtc->base,
> >>+			config->ctm_property, 0);
> >>+	drm_object_property_set_value(&crtc->base,
> >>+			config->gamma_lut_property,
> >>+			crtc->state->gamma_lut->base.id);
> >>+
> >>  	/* Driver takes ownership of state on successful commit. */
> >>  	drm_property_unreference_blob(blob);
> >>-- 
> >>2.8.0.rc3
> >>
> >>_______________________________________________
> >>dri-devel mailing list
> >>dri-devel at lists.freedesktop.org
> >>https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch