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

[Lionel Landwerlin]

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

>
> 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.


>> 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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