[PATCH] drm/amd/display: Enable PSR by default on DCN3.1

[Vishwakarma, Pratik]

On 10/8/2021 9:44 PM, Nicholas Kazlauskas wrote:
> [Why]
> New idle optimizations for DCN3.1 require PSR for optimal power savings
> on panels that support it.
>
> This was previously left disabled by default because of issues with
> compositors that do not pageflip and scan out directly to the
> frontbuffer.
>
> For these compositors we now have detection methods that wait for x
> number of pageflips after a full update - triggered by a buffer or
> format change typically.
>
> This may introduce bugs or new cases not tested by users so this is
> only currently targeting DCN31.
>
> [How]
> Add code in DM to set PSR state by default for DCN3.1 while falling
> back to the feature mask for older DCN.
>
> Add a global debug flag that can be set to disable it for either.
>
> Cc: Harry Wentland<harry.wentland at amd.com>
> Cc: Roman Li<roman.li at amd.com>
> Signed-off-by: Nicholas Kazlauskas<nicholas.kazlauskas at amd.com>
> ---
>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c   | 17 ++++++++++++++++-
>   drivers/gpu/drm/amd/include/amd_shared.h        |  5 +++--
>   2 files changed, 19 insertions(+), 3 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 dc595ecec595..ff545503a6ed 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4031,6 +4031,7 @@ static int amdgpu_dm_initialize_drm_device(struct amdgpu_device *adev)
>   	int32_t primary_planes;
>   	enum dc_connection_type new_connection_type = dc_connection_none;
>   	const struct dc_plane_cap *plane;
> +	bool psr_feature_enabled = false;
>   
>   	dm->display_indexes_num = dm->dc->caps.max_streams;
>   	/* Update the actual used number of crtc */
> @@ -4113,6 +4114,19 @@ static int amdgpu_dm_initialize_drm_device(struct amdgpu_device *adev)
>   		DRM_DEBUG_KMS("Unsupported DCN IP version for outbox: 0x%X\n",
>   			      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):
> +			psr_feature_enabled = true;
> +			break;
> +		default:
> +			psr_feature_enabled = amdgpu_dc_feature_mask & DC_PSR_MASK;
> +			break;
> +		}
> +	}
>   #endif
>   
>   	/* loops over all connectors on the board */
> @@ -4156,7 +4170,8 @@ static int amdgpu_dm_initialize_drm_device(struct amdgpu_device *adev)
>   		} else if (dc_link_detect(link, DETECT_REASON_BOOT)) {
>   			amdgpu_dm_update_connector_after_detect(aconnector);
>   			register_backlight_device(dm, link);
> -			if (amdgpu_dc_feature_mask & DC_PSR_MASK)
> +
> +			if (psr_feature_enabled)
>   				amdgpu_dm_set_psr_caps(link);
>   		}
>   
> diff --git a/drivers/gpu/drm/amd/include/amd_shared.h b/drivers/gpu/drm/amd/include/amd_shared.h
> index 257f280d3d53..f1a46d16f7ea 100644
> --- a/drivers/gpu/drm/amd/include/amd_shared.h
> +++ b/drivers/gpu/drm/amd/include/amd_shared.h
> @@ -228,7 +228,7 @@ enum DC_FEATURE_MASK {
>   	DC_FBC_MASK = (1 << 0), //0x1, disabled by default
>   	DC_MULTI_MON_PP_MCLK_SWITCH_MASK = (1 << 1), //0x2, enabled by default
>   	DC_DISABLE_FRACTIONAL_PWM_MASK = (1 << 2), //0x4, disabled by default
> -	DC_PSR_MASK = (1 << 3), //0x8, disabled by default
> +	DC_PSR_MASK = (1 << 3), //0x8, disabled by default for dcn < 3.1
>   	DC_EDP_NO_POWER_SEQUENCING = (1 << 4), //0x10, disabled by default
>   };
>   
> @@ -236,7 +236,8 @@ enum DC_DEBUG_MASK {
>   	DC_DISABLE_PIPE_SPLIT = 0x1,
>   	DC_DISABLE_STUTTER = 0x2,
>   	DC_DISABLE_DSC = 0x4,
> -	DC_DISABLE_CLOCK_GATING = 0x8
> +	DC_DISABLE_CLOCK_GATING = 0x8,
> +	DC_DISABLE_PSR = 0x10,

Don't we need a corresponding check in amdgpu_dm_init() to disable PSR 
in runtime?

Also, how does it handle conflicting declarations from feature mask and 
debug mask?

/BR
/

/Pratik
/

>   };
>   
>   enum amd_dpm_forced_level;
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