Re: [PATCH] drm/amd/display: enable/disable PSR feature at run time

[Hamza Mahfooz <hamza.mahfooz@amd.com>]

On 7/11/23 03:28, Shirish S wrote:
> [Why]
> Per current architecture, PSR feature is disabled by default for DCN < 3.

There were issues in the past with enabling PSR for < DCN3 ASICs. So,
unless we can prove those issues are gone I don't think this is advisable.

> This makes it impossible for those pre-flashed device users to try newer
> (psr capable) panels without altering OS (boot params).
> Also on Chromebooks its not sustainable to have custom dc_feature_mask.
> 
> [How]
> amdgpu_dm_set_psr_caps() in its current form does a decent job to evaluate
> and discard links that are not capable of PSR feature.
> If the current implementation has gap, going forward it needs to be
> addressed either by adding appropriate ways to detect and discard the
> panels or by iteratively blacklisting the same.
> 
> Signed-off-by: Shirish S <shirish.s@amd.com>
> ---
>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 23 ++-----------------
>   1 file changed, 2 insertions(+), 21 deletions(-)
> 
> 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 073bf00c6fdc..0fcafe1a071d 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4313,7 +4313,6 @@ static int amdgpu_dm_initialize_drm_device(struct amdgpu_device *adev)
>   	s32 primary_planes;
>   	enum dc_connection_type new_connection_type = dc_connection_none;
>   	const struct dc_plane_cap *plane;
> -	bool psr_feature_enabled = false;
>   	int max_overlay = dm->dc->caps.max_slave_planes;
>   
>   	dm->display_indexes_num = dm->dc->caps.max_streams;
> @@ -4405,24 +4404,6 @@ static int amdgpu_dm_initialize_drm_device(struct amdgpu_device *adev)
>   			      adev->ip_versions[DCE_HWIP][0]);
>   	}
>   
> -	/* Determine whether to enable PSR support by default. */
> -	if (!(amdgpu_dc_debug_mask & DC_DISABLE_PSR)) {
> -		switch (adev->ip_versions[DCE_HWIP][0]) {
> -		case IP_VERSION(3, 1, 2):
> -		case IP_VERSION(3, 1, 3):
> -		case IP_VERSION(3, 1, 4):
> -		case IP_VERSION(3, 1, 5):
> -		case IP_VERSION(3, 1, 6):
> -		case IP_VERSION(3, 2, 0):
> -		case IP_VERSION(3, 2, 1):
> -			psr_feature_enabled = true;
> -			break;
> -		default:
> -			psr_feature_enabled = amdgpu_dc_feature_mask & DC_PSR_MASK;
> -			break;
> -		}
> -	}
> -
>   	/* loops over all connectors on the board */
>   	for (i = 0; i < link_cnt; i++) {
>   		struct dc_link *link = NULL;
> @@ -4471,8 +4452,8 @@ static int amdgpu_dm_initialize_drm_device(struct amdgpu_device *adev)
>   				amdgpu_dm_update_connector_after_detect(aconnector);
>   				setup_backlight_device(dm, aconnector);
>   
> -				if (psr_feature_enabled)
> -					amdgpu_dm_set_psr_caps(link);
> +				/* Determine & Set PSR caps*/
> +				amdgpu_dm_set_psr_caps(link);
>   
>   				/* TODO: Fix vblank control helpers to delay PSR entry to allow this when
>   				 * PSR is also supported.
-- 
Hamza