Re: [PATCH 1/2] drm/i915/display: Add block_dc6_needed variable into intel_crtc

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Sep 13, 2024 at 10:33:46AM +0300, Jouni Högander wrote:
> We need to block DC6 entry in case of Panel Replay as enabling VBI doesn't
> prevent DC6 in case of Panel Replay. This causes problems if user-space is
> polling for vblank events. For this purpose add new block_dc6_needed
> variable into intel_crtc.
> 
> Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
> ---
>  .../gpu/drm/i915/display/intel_display_irq.c  | 28 +++++++++++++++++++
>  .../gpu/drm/i915/display/intel_display_irq.h  |  3 ++
>  .../drm/i915/display/intel_display_types.h    |  7 +++++
>  drivers/gpu/drm/i915/display/intel_psr.c      |  7 +++++
>  4 files changed, 45 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display_irq.c b/drivers/gpu/drm/i915/display/intel_display_irq.c
> index 8f13f148c73e3..7ff721bcec0d3 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_irq.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_irq.c
> @@ -1361,6 +1361,34 @@ static bool gen11_dsi_configure_te(struct intel_crtc *intel_crtc,
>  	return true;
>  }
>  
> +/**
> + * block_dc6_on_vblank_get - get block DC6 entry reference
> + *
> + * @_crtc: drm crtc pointer
> + *
> + * This function is called from Panel Replay code when Panel Replay gets
> + * activated. Intention is to block DC6 entry when VBI is enabled and Panel
> + * Replay is active.
> + */
> +void block_dc6_on_vblank_get(struct drm_crtc *_crtc)
> +{
> +	to_intel_crtc(_crtc)->block_dc6_needed++;
> +}
> +
> +/**
> + * block_dc6_on_vblank_put - free block DC6 entry reference
> + *
> + * @crtc: drm crtc pointer
> + *
> + * This function is called from Panel Replay code when Panel Replay is
> + * deactivated. Intention is to block DC6 entry when VBI is enabled and Panel
> + * Replay is active.
> + */
> +void block_dc6_on_vblank_put(struct drm_crtc *crtc)
> +{
> +	to_intel_crtc(crtc)->block_dc6_needed--;
> +}
> +
>  int bdw_enable_vblank(struct drm_crtc *_crtc)
>  {
>  	struct intel_crtc *crtc = to_intel_crtc(_crtc);
> diff --git a/drivers/gpu/drm/i915/display/intel_display_irq.h b/drivers/gpu/drm/i915/display/intel_display_irq.h
> index 2a090dd6abd7c..fe3ada8f37283 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_irq.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_irq.h
> @@ -77,6 +77,9 @@ void i965_pipestat_irq_handler(struct drm_i915_private *i915, u32 iir, u32 pipe_
>  void valleyview_pipestat_irq_handler(struct drm_i915_private *i915, u32 pipe_stats[I915_MAX_PIPES]);
>  void i8xx_pipestat_irq_handler(struct drm_i915_private *i915, u16 iir, u32 pipe_stats[I915_MAX_PIPES]);
>  
> +void block_dc6_on_vblank_get(struct drm_crtc *crtc);
> +void block_dc6_on_vblank_put(struct drm_crtc *crtc);
> +
>  void intel_display_irq_init(struct drm_i915_private *i915);
>  
>  #endif /* __INTEL_DISPLAY_IRQ_H__ */
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index 000ab373c8879..df0c3eb750809 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1413,6 +1413,13 @@ struct intel_crtc {
>  #ifdef CONFIG_DEBUG_FS
>  	struct intel_pipe_crc pipe_crc;
>  #endif
> +
> +	/*
> +	 * We need to block DC6 entry in case of Panel Replay as enabling VBI doesn't
> +	 * prevent DC6 in case of Panel Replay. This causes problems if user-space is
> +	 * polling for vblank events.
> +	 */
> +	u8 block_dc6_needed;
>  };
>  
>  struct intel_plane {
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index 1a4ef231a53ca..f9e5177893c46 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -35,6 +35,7 @@
>  #include "intel_cursor_regs.h"
>  #include "intel_ddi.h"
>  #include "intel_de.h"
> +#include "intel_display_irq.h"
>  #include "intel_display_types.h"
>  #include "intel_dp.h"
>  #include "intel_dp_aux.h"
> @@ -970,6 +971,9 @@ static void dg2_activate_panel_replay(struct intel_dp *intel_dp)
>  			       val);
>  	}
>  
> +	if (intel_dp_is_edp(intel_dp))
> +		block_dc6_on_vblank_get(&intel_crtc_for_pipe(display, intel_dp->psr.pipe)->base);

This still feels racy. Can't we make it just a simple flag that
gets set just once before/during intel_crtc_vblank_on()?

> +
>  	intel_de_rmw(display,
>  		     PSR2_MAN_TRK_CTL(display, intel_dp->psr.transcoder),
>  		     0, ADLP_PSR2_MAN_TRK_CTL_SF_CONTINUOS_FULL_FRAME);
> @@ -2005,6 +2009,9 @@ static void intel_psr_exit(struct intel_dp *intel_dp)
>  	}
>  
>  	if (intel_dp->psr.panel_replay_enabled) {
> +		if (intel_dp_is_edp(intel_dp))
> +			block_dc6_on_vblank_put(drm_crtc_from_index(display->drm,
> +								    intel_dp->psr.pipe));
>  		intel_de_rmw(display, TRANS_DP2_CTL(intel_dp->psr.transcoder),
>  			     TRANS_DP2_PANEL_REPLAY_ENABLE, 0);
>  	} else if (intel_dp->psr.sel_update_enabled) {
> -- 
> 2.34.1

-- 
Ville Syrjälä
Intel