Re: [PATCH 1/5] drm/i915/psr: Add helper to get min psr guardband

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

On Fri, 2025-10-17 at 18:05 +0530, Ankit Nautiyal wrote:
> Introduce a helper to compute the max link wake latency when using
> Auxless/Aux wake mechanism for PSR/Panel Replay/LOBF features.
> 
> This will be used to compute the minimum guardband so that the link
> wake
> latencies are accounted and these features work smoothly for higher
> refresh rate panels.
> 
> v2:
> - Account for flag `req_psr2_sdp_prior_scanline` and scl lines while
>   computing min guardband. (Jouni)
> - Use wake lines only for eDP with panel_replay and sel_update flags
>   set. (Jouni)
> 
> Bspec: 70151, 71477
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>

Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_psr.c | 27
> ++++++++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_psr.h |  1 +
>  2 files changed, 28 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c
> b/drivers/gpu/drm/i915/display/intel_psr.c
> index 703e5f6af04c..3cca48a4a5d3 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -4416,3 +4416,30 @@ void intel_psr_compute_config_late(struct
> intel_dp *intel_dp,
>  
>  	intel_psr_set_non_psr_pipes(intel_dp, crtc_state);
>  }
> +
> +int intel_psr_min_guardband(struct intel_crtc_state *crtc_state)
> +{
> +	struct intel_display *display =
> to_intel_display(crtc_state);
> +	int psr_min_guardband;
> +	int wake_lines;
> +
> +	if (!intel_crtc_has_type(crtc_state, INTEL_OUTPUT_EDP))
> +		return 0;
> +
> +	if (crtc_state->has_panel_replay)
> +		wake_lines = crtc_state-
> >alpm_state.aux_less_wake_lines;
> +	else if (crtc_state->has_sel_update)
> +		wake_lines = DISPLAY_VER(display) < 20 ?
> +			     psr2_block_count_lines(crtc_state-
> >alpm_state.io_wake_lines,
> +						    crtc_state-
> >alpm_state.fast_wake_lines) :
> +			     crtc_state->alpm_state.io_wake_lines;
> +	else
> +		return 0;
> +
> +	psr_min_guardband = wake_lines + crtc_state-
> >set_context_latency;
> +
> +	if (crtc_state->req_psr2_sdp_prior_scanline)
> +		psr_min_guardband++;
> +
> +	return psr_min_guardband;
> +}
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.h
> b/drivers/gpu/drm/i915/display/intel_psr.h
> index b17ce312dc37..620b35928832 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.h
> +++ b/drivers/gpu/drm/i915/display/intel_psr.h
> @@ -85,5 +85,6 @@ bool intel_psr_needs_alpm_aux_less(struct intel_dp
> *intel_dp,
>  				   const struct intel_crtc_state
> *crtc_state);
>  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);
>  
>  #endif /* __INTEL_PSR_H__ */