[PATCH v7] drm/i915/panelreplay: Panel replay workaround with VRR

[Ville Syrjälä]

On Tue, Jun 18, 2024 at 04:52:15PM +0530, Animesh Manna wrote:
> Panel Replay VSC SDP not getting sent when VRR is enabled
> and W1 and W2 are 0. So Program Set Context Latency in
> TRANS_SET_CONTEXT_LATENCY register to at least a value of 1.
> 
> HSD: 14015406119
> 
> v1: Initial version.
> v2: Update timings stored in adjusted_mode struct. [Ville]
> v3: Add WA in compute_config(). [Ville]
> v4:
> - Add DISPLAY_VER() check and improve code comment. [Rodrigo]
> - Introduce centralized intel_crtc_vblank_delay(). [Ville]
> v5: Move to crtc_compute_config(). [Ville]
> v6: Restrict DISPLAY_VER till 14. [Mitul]
> v7:
> - Corrected code-comment. [Mitul]
> - dev_priv local variable removed. [Jani]
> 
> Reviewed-by: Mitul Golani <mitulkumar.ajitkumar.golani at intel.com>
> Signed-off-by: Animesh Manna <animesh.manna at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 21 ++++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_display.h |  1 +
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 7bc4f3de691e..c3ff3a5c5fa3 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -2515,6 +2515,10 @@ static int intel_crtc_compute_config(struct intel_atomic_state *state,
>  		intel_atomic_get_new_crtc_state(state, crtc);
>  	int ret;
>  
> +	/* wa_14015401596: display versions 13, 14 */
> +	if (IS_DISPLAY_VER(to_i915(crtc->base.dev), 13, 14))
> +		intel_crtc_vblank_delay(crtc_state);
> +
>  	ret = intel_dpll_crtc_compute_clock(state, crtc);
>  	if (ret)
>  		return ret;
> @@ -3924,6 +3928,23 @@ bool intel_crtc_get_pipe_config(struct intel_crtc_state *crtc_state)
>  	return true;
>  }
>  
> +void intel_crtc_vblank_delay(struct intel_crtc_state *crtc_state)
> +{
> +	struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
> +
> +	/*
> +	 * wa_14015401596 for display versions 13, 14.
> +	 * Program Set Context Latency in TRANS_SET_CONTEXT_LATENCY register
> +	 * to at least a value of 1 when Panel Replay is enabled with VRR.
> +	 * Value for TRANS_SET_CONTEXT_LATENCY is calculated by substracting
> +	 * crtc_vdisplay from crtc_vblank_start, so incrementing crtc_vblank_start
> +	 * by 1 if both are equal.
> +	 */
> +	if (crtc_state->vrr.enable && crtc_state->has_panel_replay &&
> +	    adjusted_mode->crtc_vblank_start == adjusted_mode->crtc_vdisplay)
> +		adjusted_mode->crtc_vblank_start += 1;
> +}

This is probably too late actually. We already used the previous value
to calculate the VRR guardband/pipeline full values, which may or may
not now be incorrect. So NAK for now until someone actually checks how
it all works (I don't recall the details right now).

> +
>  int intel_dotclock_calculate(int link_freq,
>  			     const struct intel_link_m_n *m_n)
>  {
> diff --git a/drivers/gpu/drm/i915/display/intel_display.h b/drivers/gpu/drm/i915/display/intel_display.h
> index b0cf6ca70952..f99a24e76608 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.h
> +++ b/drivers/gpu/drm/i915/display/intel_display.h
> @@ -428,6 +428,7 @@ bool intel_crtc_is_joiner_primary(const struct intel_crtc_state *crtc_state);
>  u8 intel_crtc_joiner_secondary_pipes(const struct intel_crtc_state *crtc_state);
>  struct intel_crtc *intel_primary_crtc(const struct intel_crtc_state *crtc_state);
>  bool intel_crtc_get_pipe_config(struct intel_crtc_state *crtc_state);
> +void intel_crtc_vblank_delay(struct intel_crtc_state *crtc_state);
>  bool intel_pipe_config_compare(const struct intel_crtc_state *current_config,
>  			       const struct intel_crtc_state *pipe_config,
>  			       bool fastset);
> -- 
> 2.29.0

-- 
Ville Syrjälä
Intel