Re: [RFC PATCH] drm/i915/psr: Prevent DC entry during active vblank for Panel Replay

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Tue, 2026-04-28 at 18:09 +0530, Dibin Moolakadan Subrahmanian wrote:
> On PTL+ (display ver >= 30), hold the DMC wakelock while vblank is
> enabled for Panel Replay. Older platforms rely on
> intel_display_power_set_target_dc_state() for this.
> 
> The wakelock is acquired/released at two places:
> 1) Dynamically when vblank is enabled/disabled via
>    intel_psr_notify_vblank_enable_disable().
> 2) In the PSR enable/disable path.
> 
> This handles the following ordering scenarios:
> 1) Panel Replay is enabled before vblank enable arrives.
> 2) Vblank enable arrives before Panel Replay is updated in
>    intel_psr_post_plane_update().

As discussed offline I would check if we could just take the wakelock
when VBI is getting enabled.

BR,
Jouni Högander

> ---
>  .../drm/i915/display/intel_display_types.h    |  2 +
>  drivers/gpu/drm/i915/display/intel_psr.c      | 55
> +++++++++++++++++--
>  2 files changed, 53 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h
> b/drivers/gpu/drm/i915/display/intel_display_types.h
> index c81916761850..f386d6dba9e5 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1775,6 +1775,8 @@ struct intel_psr {
>  	bool source_panel_replay_support;
>  	bool sink_panel_replay_support;
>  	bool panel_replay_enabled;
> +	bool panel_replay_wakelock;
> +	bool vblank_enabled;
>  	u32 dc3co_exitline;
>  	u32 dc3co_exit_delay;
>  	struct delayed_work dc3co_work;
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c
> b/drivers/gpu/drm/i915/display/intel_psr.c
> index 63c19958a9e3..82bc63054906 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -2192,6 +2192,34 @@ static bool psr_interrupt_error_check(struct
> intel_dp *intel_dp)
>  	return true;
>  }
>  
> +static void intel_panel_replay_get_wakelock_locked(struct intel_dp
> *intel_dp)
> +{
> +	struct intel_display *display = to_intel_display(intel_dp);
> +
> +	if (DISPLAY_VER(display) < 30)
> +		return;
> +
> +	if (intel_dp->psr.panel_replay_wakelock)
> +		return;
> +
> +	intel_dmc_wl_get_noreg(display);
> +	intel_dp->psr.panel_replay_wakelock = true;
> +}
> +
> +static void intel_panel_replay_put_wakelock_locked(struct intel_dp
> *intel_dp)
> +{
> +	struct intel_display *display = to_intel_display(intel_dp);
> +
> +	if (DISPLAY_VER(display) < 30)
> +		return;
> +
> +	if (!intel_dp->psr.panel_replay_wakelock)
> +		return;
> +
> +	intel_dmc_wl_put_noreg(display);
> +	intel_dp->psr.panel_replay_wakelock = false;
> +}
> +
>  static void intel_psr_enable_locked(struct intel_dp *intel_dp,
>  				    const struct intel_crtc_state
> *crtc_state)
>  {
> @@ -2224,8 +2252,11 @@ static void intel_psr_enable_locked(struct
> intel_dp *intel_dp,
>  	if (!psr_interrupt_error_check(intel_dp))
>  		return;
>  
> -	if (intel_dp->psr.panel_replay_enabled)
> +	if (intel_dp->psr.panel_replay_enabled) {
> +		if (intel_dp->psr.vblank_enabled)
> +			intel_panel_replay_get_wakelock_locked(intel
> _dp);
>  		drm_dbg_kms(display->drm, "Enabling Panel
> Replay\n");
> +	}
>  	else
>  		drm_dbg_kms(display->drm, "Enabling PSR%s\n",
>  			    intel_dp->psr.sel_update_enabled ? "2" :
> "1");
> @@ -2344,8 +2375,10 @@ static void intel_psr_disable_locked(struct
> intel_dp *intel_dp)
>  	if (!intel_dp->psr.enabled)
>  		return;
>  
> -	if (intel_dp->psr.panel_replay_enabled)
> +	if (intel_dp->psr.panel_replay_enabled) {
> +		intel_panel_replay_put_wakelock_locked(intel_dp);
>  		drm_dbg_kms(display->drm, "Disabling Panel
> Replay\n");
> +	}
>  	else
>  		drm_dbg_kms(display->drm, "Disabling PSR%s\n",
>  			    intel_dp->psr.sel_update_enabled ? "2" :
> "1");
> @@ -4143,9 +4176,24 @@ void
> intel_psr_notify_vblank_enable_disable(struct intel_display *display,
>  		struct intel_dp *intel_dp =
> enc_to_intel_dp(encoder);
>  
>  		mutex_lock(&intel_dp->psr.lock);
> +		intel_dp->psr.vblank_enabled = enable;
>  		if (intel_dp->psr.panel_replay_enabled) {
> +			/*
> +			 * wakelock handling for panel replay
> +			 * for older platform rely on
> intel_display_power_set_target_dc_state().
> +			 */
> +			if (DISPLAY_VER(display) < 30) {
> +				mutex_unlock(&intel_dp->psr.lock);
> +				break;
> +			}
> +
> +			if (enable)
> +				intel_panel_replay_get_wakelock_lock
> ed(intel_dp);
> +			else
> +				intel_panel_replay_put_wakelock_lock
> ed(intel_dp);
> +
>  			mutex_unlock(&intel_dp->psr.lock);
> -			break;
> +			return;
>  		}
>  
>  		if (intel_dp->psr.enabled && intel_dp-
> >psr.pkg_c_latency_used)
> @@ -4154,7 +4202,6 @@ void
> intel_psr_notify_vblank_enable_disable(struct intel_display *display,
>  		mutex_unlock(&intel_dp->psr.lock);
>  		return;
>  	}
> -
>  	/*
>  	 * NOTE: intel_display_power_set_target_dc_state is used
>  	 * only by PSR * code for DC3CO handling. DC3CO target