Re: [PATCH v9 6/8] drm/i915/psr: Wait for idle only after possible send push

["Nautiyal, Ankit K" <ankit.k.nautiyal@intel.com>]

On 12/23/2025 4:21 PM, Jouni Högander wrote:
> We are planning to move using trans push mechanism to trigger the Frame
> Change event. in that case we can't wait PSR to idle before send push
> happens. Due to this move wait for idle to be done after possible send push
> is done.
>
> This should be ok for Frame Change event triggered by register write as
> well. Wait for idle is needed only for corner case where PSR is
> transitioning into DEEP_SLEEP when Frame Change event is triggered. It just
> has to be before wait for vblank. Otherwise we may have vblank before PSR
> enters DEEP_SLEEP and still using old frame buffers for first frame after
> wake up.
>
> Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
> ---
>   drivers/gpu/drm/i915/display/intel_display.c | 13 ++++++++++---
>   1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index c7ca4f53b8b8..1aca4802b7d5 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -7333,9 +7333,6 @@ static void intel_atomic_dsb_finish(struct intel_atomic_state *state,
>   		intel_psr_trigger_frame_change_event(new_crtc_state->dsb_commit,
>   						     state, crtc);
>   
> -		intel_psr_wait_for_idle_dsb(new_crtc_state->dsb_commit,
> -					    new_crtc_state);
> -
>   		if (new_crtc_state->use_dsb)
>   			intel_dsb_vblank_evade(state, new_crtc_state->dsb_commit);
>   
> @@ -7375,6 +7372,16 @@ static void intel_atomic_dsb_finish(struct intel_atomic_state *state,
>   
>   		intel_vrr_send_push(new_crtc_state->dsb_commit, new_crtc_state);
>   
> +		/*
> +		 * Wait for idle is needed for corner case where PSR HW
> +		 * is transitioning into DEEP_SLEEP/SRDENT_OFF when
> +		 * new Frame Change event comes in. It is ok to do it
> +		 * here for both Frame Change mecanisms (trans push
> +		 * and register write).
> +		 */
> +		intel_psr_wait_for_idle_dsb(new_crtc_state->dsb_commit,
> +					    new_crtc_state);
> +

If I understand correctly:

For Fixed RR case:
Suppose we are in PSR:
Skip_wait_en is set.
The portion around the Send Push will be like:


-dsb_wait_vblank will no longer wait for the undelayed vblank (we are in 
PSR and skip_wait_en is set)
-we send push -> to trigger frame change event for PSR HW.

-After this PSR HW is supposed to receive the event and may be in 
transition period so we wait for idle dsb.(which internally makes sure 
that we are out of PSR)

-We are not sure whether we are in active or in vblank region at this 
point of time so we want to use dsb_wait_vblank. The skip_wait_en will 
now not come in picture since we have made sure that we are not in PSR 
in previous step.

Then other steps will be similar to what we have been doing.

Is my understanding correct?

What happens when Panel Replay is in picture, given we can have PR 
enable with Variable Refresh Rate timings.


Regards,

Ankit

>   		/*
>   		 * In case PSR uses trans push as a "frame change" event and
>   		 * VRR is not in use we need to wait vblank. Othervise we may