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

[Lionel Landwerlin]

On 12/04/16 17:07, Daniel Vetter wrote:
> 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.

Sorry for the late answer, there is no issue if we're running with 
i915.nuclear_flip=1.
Should we go with Bob's patch then? :

https://patchwork.freedesktop.org/patch/80112/

>
>>> 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

Will do.

>
>>
>>>> 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
>>>>
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