Re: [PATCH 1/4] drm/i915/psr: Add helper for checking if vblank evasion is needed by PSR

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 25 Nov 2025, Jouni Högander <jouni.hogander@intel.com> wrote:
> PSR2_MAN_TRK_CTL[SF Continuous full frame] is sampled on the rising edge of
> delayed vblank. SW must ensure this bit is not changing around that
> bit. Due to this PSR2 Selective Fetch needs vblank evasion.
>
> Due to this add helper for intel_pipe_update_start usage to choose if
> vblank evasion is needed by PSR.
>
> Bspec: 50424
> Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_psr.c | 15 +++++++++++++++
>  drivers/gpu/drm/i915/display/intel_psr.h |  1 +
>  2 files changed, 16 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index 08bca4573974..18d5fe992f58 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -4540,3 +4540,18 @@ int intel_psr_min_guardband(struct intel_crtc_state *crtc_state)
>  
>  	return psr_min_guardband;
>  }
> +
> +bool intel_psr_needs_evasion(const struct intel_crtc_state *crtc_state)
> +{
> +	struct intel_display *display = to_intel_display(crtc_state);
> +	struct intel_encoder *encoder;
> +	struct intel_dp *intel_dp;
> +
> +	for_each_intel_encoder_mask_with_psr(display->drm, encoder,
> +					     crtc_state->uapi.encoder_mask) {
> +		intel_dp = enc_to_intel_dp(encoder);
> +
> +		break;
> +	}
> +	return intel_dp->psr.psr2_sel_fetch_enabled;

This is going to trigger a static analyzer error on unused variable
intel_dp.

Better to have the return inside the loop, and return false at the end,
I think.

BR,
Jani.

> +}
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.h b/drivers/gpu/drm/i915/display/intel_psr.h
> index 620b35928832..8c09a9f8a00e 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.h
> +++ b/drivers/gpu/drm/i915/display/intel_psr.h
> @@ -86,5 +86,6 @@ bool intel_psr_needs_alpm_aux_less(struct intel_dp *intel_dp,
>  void intel_psr_compute_config_late(struct intel_dp *intel_dp,
>  				   struct intel_crtc_state *crtc_state);
>  int intel_psr_min_guardband(struct intel_crtc_state *crtc_state);
> +bool intel_psr_needs_evasion(const struct intel_crtc_state *crtc_state);
>  
>  #endif /* __INTEL_PSR_H__ */

-- 
Jani Nikula, Intel