[PATCH] drm/amd/display: Disallow enabling CRTC without primary plane with FB

[Harry Wentland]

On 2018-04-19 03:43 AM, Michel Dänzer wrote:
> 
> [ Dropping stable@ (fixes with Cc: stable are picked up for stable
> branches once they land in Linus' tree, there's no point sending them to
> stable@ during review), adding dri-devel ]
> 
> On 2018-04-18 10:26 PM, Harry Wentland wrote:
>> The below commit
>>
>>     "drm/atomic: Try to preserve the crtc enabled state in drm_atomic_remove_fb, v2"
>>
>> introduces a slight behavioral change to rmfb. Instead of disabling a crtc
>> when the primary plane is disabled, it now preserves it.
>>
>> Since DC is currently not equipped to handle this we need to fail such
>> a commit, otherwise we might see a corrupted screen.
> 
> How does the caller react to failing such a commit?

The caller (drm_atomic_remove_fb in this case) will retry with the old behavior and disable the CRTC.

Harry

> 
> 
>> This is based on Shirish's previous approach but avoids adding all
>> planes to the new atomic state which leads to a full update in DC for
>> any commit, and is not what we intend.
>>
>> Theoretically DM should be able to deal with states with fully populated planes,
>> even for simple updates, such as cursor updates. This should still be
>> addressed in the future.
>>
>> Signed-off-by: Harry Wentland <harry.wentland at amd.com>
>> Cc: stable at vger.kernel.org
>> ---
>>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 10 +++++++++-
>>  1 file changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> index 6f92a19bebd6..0bdc6b484bad 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -4683,6 +4683,7 @@ static int dm_update_crtcs_state(struct amdgpu_display_manager *dm,
>>  		struct amdgpu_dm_connector *aconnector = NULL;
>>  		struct drm_connector_state *new_con_state = NULL;
>>  		struct dm_connector_state *dm_conn_state = NULL;
>> +		struct drm_plane_state *new_plane_state = NULL;
>>  
>>  		new_stream = NULL;
>>  
>> @@ -4690,6 +4691,13 @@ static int dm_update_crtcs_state(struct amdgpu_display_manager *dm,
>>  		dm_new_crtc_state = to_dm_crtc_state(new_crtc_state);
>>  		acrtc = to_amdgpu_crtc(crtc);
>>  
>> +		new_plane_state = drm_atomic_get_new_plane_state(state, new_crtc_state->crtc->primary);
>> +
>> +		if (new_crtc_state->enable && new_plane_state && !new_plane_state->fb) {
>> +			ret = -EINVAL;
>> +			goto fail;
>> +		}
>> +
>>  		aconnector = amdgpu_dm_find_first_crtc_matching_connector(state, crtc);
>>  
>>  		/* TODO This hack should go away */
>> @@ -4894,7 +4902,7 @@ static int dm_update_planes_state(struct dc *dc,
>>  			if (!dm_old_crtc_state->stream)
>>  				continue;
>>  
>> -			DRM_DEBUG_DRIVER("Disabling DRM plane: %d on DRM crtc %d\n",
>> +			DRM_DEBUG_ATOMIC("Disabling DRM plane: %d on DRM crtc %d\n",
>>  					plane->base.id, old_plane_crtc->base.id);
>>  
>>  			if (!dc_remove_plane_from_context(
>>
> 
>