Re: [Intel-gfx] [PATCH] drm/i915: Do a better job at disabling primary plane in the noatomic case.

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 12-11-15 om 14:37 schreef Ander Conselvan De Oliveira:
> On Wed, 2015-11-11 at 15:36 +0100, Maarten Lankhorst wrote:
>> When disable_noatomic is called plane_mask is not reliable yet,
>> and plane_state->visible = true even after disabling the primary plane.
> So the stale value of plane_state->visible causes a subsequent modeset to enable
> the primary again?
Probably not because it would get recalculated in calc_changes, but it should really be set to false afterwards.

in intel_plane_atomic_calc_changes:
if (!was_crtc_enabled && WARN_ON(was_visible))
was_visible = false;

and in intel_sanitize_crtc when intel_check_plane_mapping fails, it gets set to true to disable it.

This is really a special case and it's for disable_noatomic only. As the name says it can't rely on the atomic state.

>> Fix this by unsetting plane->visible if it was visible, and calling
>> disable_planes with the primary plane as mask.
>>
>> The other planes are already disabled in intel_sanitize_crtc, so
>> they don't have to be handled here.
>>
>> Cc: stable@vger.kernel.org #v4.3, v4.2?
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92655
>> Tested-by: Tomas Mezzadra <tmezzadra@gmail.com>
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> ---
>>  drivers/gpu/drm/i915/intel_display.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_display.c
>> b/drivers/gpu/drm/i915/intel_display.c
>> index b5f7493213b7..bc3282ab5ed2 100644
>> --- a/drivers/gpu/drm/i915/intel_display.c
>> +++ b/drivers/gpu/drm/i915/intel_display.c
>> @@ -6267,9 +6267,11 @@ static void intel_crtc_disable_noatomic(struct drm_crtc
>> *crtc)
>>  		WARN_ON(intel_crtc->unpin_work);
>>  
>>  		intel_pre_disable_primary(crtc);
>> +
>> +		intel_crtc_disable_planes(crtc, 1 << drm_plane_index(crtc
>> ->primary));
>> +		to_intel_plane_state(crtc->primary->state)->visible = false;
>>  	}
>>  
>> -	intel_crtc_disable_planes(crtc, crtc->state->plane_mask);
> Can't we just make plane_mask reliable? We know whether the primary plane is
> enabled and all others were disabled prior to that. Or did I miss something.
>
In the case of hardware readout you can't. The plane_mask gets set only if we can preserve the initial framebuffer
else the primary plane gets disabled.

~Maarten