Re: [PATCH v3 1/2] drm/i915/display: Add block_dc6_needed variable into intel_crtc

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

On Tue, Sep 17, 2024 at 09:35:59AM +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. Check if eDP Panel Replay is possible and set the
> variable accordingly.
> 
> v3: check that encoder is dp
> v2: set/clear block_dc6_needed in intel_crtc_vblank_on/off
> 
> Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_crtc.c       | 17 +++++++++++++++++
>  .../gpu/drm/i915/display/intel_display_types.h  |  7 +++++++
>  drivers/gpu/drm/i915/display/intel_psr.c        |  1 +
>  3 files changed, 25 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_crtc.c b/drivers/gpu/drm/i915/display/intel_crtc.c
> index aed3853952be8..34a60b5b1e55b 100644
> --- a/drivers/gpu/drm/i915/display/intel_crtc.c
> +++ b/drivers/gpu/drm/i915/display/intel_crtc.c
> @@ -24,6 +24,7 @@
>  #include "intel_display_irq.h"
>  #include "intel_display_trace.h"
>  #include "intel_display_types.h"
> +#include "intel_dp.h"
>  #include "intel_drrs.h"
>  #include "intel_dsi.h"
>  #include "intel_fifo_underrun.h"
> @@ -123,6 +124,20 @@ u32 intel_crtc_max_vblank_count(const struct intel_crtc_state *crtc_state)
>  void intel_crtc_vblank_on(const struct intel_crtc_state *crtc_state)
>  {
>  	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> +	struct intel_encoder *encoder;
> +
> +	for_each_encoder_on_crtc(crtc->base.dev, &crtc->base, encoder) {
> +		struct intel_dp *intel_dp;
> +
> +		if (!intel_encoder_is_dp(encoder))
> +			continue;
> +
> +		intel_dp = enc_to_intel_dp(encoder);
> +
> +		if (intel_dp_is_edp(intel_dp) &&
> +		    CAN_PANEL_REPLAY(intel_dp))
> +			crtc->block_dc6_needed = true;
> +	}

This could just a function provided by intel_psr.c so that
we don't have to to see any of the details.

Is there some reason this isn't simply looking at
crtc_state->has_panel_replay?

>  
>  	assert_vblank_disabled(&crtc->base);
>  	drm_crtc_set_max_vblank_count(&crtc->base,
> @@ -150,6 +165,8 @@ void intel_crtc_vblank_off(const struct intel_crtc_state *crtc_state)
>  
>  	drm_crtc_vblank_off(&crtc->base);
>  	assert_vblank_disabled(&crtc->base);
> +
> +	crtc->block_dc6_needed = false;
>  }
>  
>  struct intel_crtc_state *intel_crtc_state_alloc(struct intel_crtc *crtc)
> 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.
> +	 */

We should point out the fact that panel replay turns the
link off only while in DC states. Otherwise I'm sure to
get confused by this again in the future.

> +	u8 block_dc6_needed;

That sounds a bit too generic perhaps. block_dc_for_vblank or something?

>  };
>  
>  struct intel_plane {
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index 4f29ac32ff85b..957f470b08fe8 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"
> -- 
> 2.34.1

-- 
Ville Syrjälä
Intel