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

["S, Shirish" <sshankar@amd.com>]

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On 4/19/2018 8:08 PM, Harry Wentland wrote:
> 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
That's the fall back logic suggested in the patch that caused this issue.

This patch is  Reviewed-by: Shirish S <shirish.s@amd.com 
<mailto:harry.wentland@amd.com>>

Regards,

Shirish S

>>
>>> 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@amd.com>
>>> Cc: stable@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(
>>>
>>


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