[PATCH 3/3] drm/amd/display: Compensate for pre-DCE12 BTR-VRR hw limitations. (v3)

[Kazlauskas, Nicholas]

On 4/26/19 5:40 PM, Mario Kleiner wrote:
> Pre-DCE12 needs special treatment for BTR / low framerate
> compensation for more stable behaviour:
> 
> According to comments in the code and some testing on DCE-8
> and DCE-11, DCE-11 and earlier only apply VTOTAL_MIN/MAX
> programming with a lag of one frame, so the special BTR hw
> programming for intermediate fixed duration frames must be
> done inside the current frame at flip submission in atomic
> commit tail, ie. one vblank earlier, and the fixed refresh
> intermediate frame mode must be also terminated one vblank
> earlier on pre-DCE12 display engines.
> 
> To achieve proper termination on < DCE-12 shift the point
> when the switch-back from fixed vblank duration to variable
> vblank duration happens from the start of VBLANK (vblank irq,
> as done on DCE-12+) to back-porch or end of VBLANK (handled
> by vupdate irq handler). We must leave the switch-back code
> inside VBLANK irq for DCE12+, as before.
> 
> Doing this, we get much better behaviour of BTR for up-sweeps,
> ie. going from short to long frame durations (~high to low fps)
> and for constant framerate flips, as tested on DCE-8 and
> DCE-11. Behaviour is still not quite as good as on DCN-1
> though.
> 
> On down-sweeps, going from long to short frame durations
> (low fps to high fps) < DCE-12 is a little bit improved,
> although by far not as much as for up-sweeps and constant
> fps.
> 
> v2: Fix some wrong locking, as pointed out by Nicholas.
> v3: Simplify if-condition in vupdate-irq - nit by Nicholas.
> Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com>

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>

I'd like to push patches 1+3 if you're okay with this.

I can see the value in the 2nd patch from the graphs and test 
application you've posted but it'll likely take some time to do thorough 
review and testing on this.

The question that needs to be examined with the second is what the 
optimal margin is, if any, for typical usecases across common monitor 
ranges. Not all monitors that support BTR have the same range, and many 
have a lower bound of ~48Hz. To me ~53Hz sounds rather early to be 
entering, but I'm not sure how it affects the user experience overall.

Nicholas Kazlauskas

> ---
>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 48 +++++++++++++++++--
>   1 file changed, 44 insertions(+), 4 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 76b6e621793f..92b3c2cec7dd 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -364,6 +364,7 @@ static void dm_vupdate_high_irq(void *interrupt_params)
>   	struct amdgpu_device *adev = irq_params->adev;
>   	struct amdgpu_crtc *acrtc;
>   	struct dm_crtc_state *acrtc_state;
> +	unsigned long flags;
>   
>   	acrtc = get_crtc_by_otg_inst(adev, irq_params->irq_src - IRQ_TYPE_VUPDATE);
>   
> @@ -379,8 +380,25 @@ static void dm_vupdate_high_irq(void *interrupt_params)
>   		 * page-flip completion events that have been queued to us
>   		 * if a pageflip happened inside front-porch.
>   		 */
> -		if (amdgpu_dm_vrr_active(acrtc_state))
> +		if (amdgpu_dm_vrr_active(acrtc_state)) {
>   			drm_crtc_handle_vblank(&acrtc->base);
> +
> +			/* BTR processing for pre-DCE12 ASICs */
> +			if (acrtc_state->stream &&
> +			    adev->family < AMDGPU_FAMILY_AI) {
> +				spin_lock_irqsave(&adev->ddev->event_lock, flags);
> +				mod_freesync_handle_v_update(
> +				    adev->dm.freesync_module,
> +				    acrtc_state->stream,
> +				    &acrtc_state->vrr_params);
> +
> +				dc_stream_adjust_vmin_vmax(
> +				    adev->dm.dc,
> +				    acrtc_state->stream,
> +				    &acrtc_state->vrr_params.adjust);
> +				spin_unlock_irqrestore(&adev->ddev->event_lock, flags);
> +			}
> +		}
>   	}
>   }
>   
> @@ -390,6 +408,7 @@ static void dm_crtc_high_irq(void *interrupt_params)
>   	struct amdgpu_device *adev = irq_params->adev;
>   	struct amdgpu_crtc *acrtc;
>   	struct dm_crtc_state *acrtc_state;
> +	unsigned long flags;
>   
>   	acrtc = get_crtc_by_otg_inst(adev, irq_params->irq_src - IRQ_TYPE_VBLANK);
>   
> @@ -412,9 +431,10 @@ static void dm_crtc_high_irq(void *interrupt_params)
>   		 */
>   		amdgpu_dm_crtc_handle_crc_irq(&acrtc->base);
>   
> -		if (acrtc_state->stream &&
> +		if (acrtc_state->stream && adev->family >= AMDGPU_FAMILY_AI &&
>   		    acrtc_state->vrr_params.supported &&
>   		    acrtc_state->freesync_config.state == VRR_STATE_ACTIVE_VARIABLE) {
> +			spin_lock_irqsave(&adev->ddev->event_lock, flags);
>   			mod_freesync_handle_v_update(
>   				adev->dm.freesync_module,
>   				acrtc_state->stream,
> @@ -424,6 +444,7 @@ static void dm_crtc_high_irq(void *interrupt_params)
>   				adev->dm.dc,
>   				acrtc_state->stream,
>   				&acrtc_state->vrr_params.adjust);
> +			spin_unlock_irqrestore(&adev->ddev->event_lock, flags);
>   		}
>   	}
>   }
> @@ -4878,8 +4899,10 @@ static void update_freesync_state_on_stream(
>   	struct dc_plane_state *surface,
>   	u32 flip_timestamp_in_us)
>   {
> -	struct mod_vrr_params vrr_params = new_crtc_state->vrr_params;
> +	struct mod_vrr_params vrr_params;
>   	struct dc_info_packet vrr_infopacket = {0};
> +	struct amdgpu_device *adev = dm->adev;
> +	unsigned long flags;
>   
>   	if (!new_stream)
>   		return;
> @@ -4892,6 +4915,9 @@ static void update_freesync_state_on_stream(
>   	if (!new_stream->timing.h_total || !new_stream->timing.v_total)
>   		return;
>   
> +	spin_lock_irqsave(&adev->ddev->event_lock, flags);
> +	vrr_params = new_crtc_state->vrr_params;
> +
>   	if (surface) {
>   		mod_freesync_handle_preflip(
>   			dm->freesync_module,
> @@ -4899,6 +4925,12 @@ static void update_freesync_state_on_stream(
>   			new_stream,
>   			flip_timestamp_in_us,
>   			&vrr_params);
> +
> +		if (adev->family < AMDGPU_FAMILY_AI &&
> +		    amdgpu_dm_vrr_active(new_crtc_state)) {
> +			mod_freesync_handle_v_update(dm->freesync_module,
> +						     new_stream, &vrr_params);
> +		}
>   	}
>   
>   	mod_freesync_build_vrr_infopacket(
> @@ -4930,6 +4962,8 @@ static void update_freesync_state_on_stream(
>   			      new_crtc_state->base.crtc->base.id,
>   			      (int)new_crtc_state->base.vrr_enabled,
>   			      (int)vrr_params.state);
> +
> +	spin_unlock_irqrestore(&adev->ddev->event_lock, flags);
>   }
>   
>   static void pre_update_freesync_state_on_stream(
> @@ -4937,8 +4971,10 @@ static void pre_update_freesync_state_on_stream(
>   	struct dm_crtc_state *new_crtc_state)
>   {
>   	struct dc_stream_state *new_stream = new_crtc_state->stream;
> -	struct mod_vrr_params vrr_params = new_crtc_state->vrr_params;
> +	struct mod_vrr_params vrr_params;
>   	struct mod_freesync_config config = new_crtc_state->freesync_config;
> +	struct amdgpu_device *adev = dm->adev;
> +	unsigned long flags;
>   
>   	if (!new_stream)
>   		return;
> @@ -4950,6 +4986,9 @@ static void pre_update_freesync_state_on_stream(
>   	if (!new_stream->timing.h_total || !new_stream->timing.v_total)
>   		return;
>   
> +	spin_lock_irqsave(&adev->ddev->event_lock, flags);
> +	vrr_params = new_crtc_state->vrr_params;
> +
>   	if (new_crtc_state->vrr_supported &&
>   	    config.min_refresh_in_uhz &&
>   	    config.max_refresh_in_uhz) {
> @@ -4970,6 +5009,7 @@ static void pre_update_freesync_state_on_stream(
>   			sizeof(vrr_params.adjust)) != 0);
>   
>   	new_crtc_state->vrr_params = vrr_params;
> +	spin_unlock_irqrestore(&adev->ddev->event_lock, flags);
>   }
>   
>   static void amdgpu_dm_handle_vrr_transition(struct dm_crtc_state *old_state,
>