[Intel-gfx] [PATCH 4/4] drm/i915/vrr: Be more careful with the bits in TRANS_VRR_CTL

[Navare, Manasi]

On Fri, Dec 02, 2022 at 03:44:12PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> On mtl (at least) clearing the guardband bits in the same write
> as the enable bit gets cleared seems to cause an immediate FIFO
> underrun. Thus is seems that we need to first clear just the
> enable bit, then wait for the VRR live status to indicate the
> transcoder has exited VRR mode (this step is documented in Bspec
> as well), and finally we can clear out the rest of the TRANS_VRR_CTL
> for good measure.
> 
> I did this without any RMWs in case we want to toggle VRR on/off
> via DSB in the future, and as we know DSB can't read registers.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Reviewed-by: Manasi Navare <manasi.d.navare at intel.com>

Manasi

> ---
>  drivers/gpu/drm/i915/display/intel_vrr.c | 40 +++++++++++++++---------
>  1 file changed, 25 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
> index 753e7b211708..5ff6aed9575e 100644
> --- a/drivers/gpu/drm/i915/display/intel_vrr.c
> +++ b/drivers/gpu/drm/i915/display/intel_vrr.c
> @@ -161,31 +161,36 @@ intel_vrr_compute_config(struct intel_crtc_state *crtc_state,
>  	crtc_state->mode_flags |= I915_MODE_FLAG_VRR;
>  }
>  
> -void intel_vrr_enable(struct intel_encoder *encoder,
> -		      const struct intel_crtc_state *crtc_state)
> +static u32 trans_vrr_ctl(const struct intel_crtc_state *crtc_state)
>  {
> -	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> -	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
> -	u32 trans_vrr_ctl;
> +	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
>  
> -	if (!crtc_state->vrr.enable)
> -		return;
> -
> -	if (DISPLAY_VER(dev_priv) >= 13)
> -		trans_vrr_ctl = VRR_CTL_VRR_ENABLE |
> -			VRR_CTL_IGN_MAX_SHIFT | VRR_CTL_FLIP_LINE_EN |
> +	if (DISPLAY_VER(i915) >= 13)
> +		return VRR_CTL_IGN_MAX_SHIFT | VRR_CTL_FLIP_LINE_EN |
>  			XELPD_VRR_CTL_VRR_GUARDBAND(crtc_state->vrr.guardband);
>  	else
> -		trans_vrr_ctl = VRR_CTL_VRR_ENABLE |
> -			VRR_CTL_IGN_MAX_SHIFT | VRR_CTL_FLIP_LINE_EN |
> +		return VRR_CTL_IGN_MAX_SHIFT | VRR_CTL_FLIP_LINE_EN |
>  			VRR_CTL_PIPELINE_FULL(crtc_state->vrr.pipeline_full) |
>  			VRR_CTL_PIPELINE_FULL_OVERRIDE;
> +}
> +
> +void intel_vrr_enable(struct intel_encoder *encoder,
> +		      const struct intel_crtc_state *crtc_state)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> +	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
> +
> +	if (!crtc_state->vrr.enable)
> +		return;
>  
>  	intel_de_write(dev_priv, TRANS_VRR_VMIN(cpu_transcoder), crtc_state->vrr.vmin - 1);
>  	intel_de_write(dev_priv, TRANS_VRR_VMAX(cpu_transcoder), crtc_state->vrr.vmax - 1);
> -	intel_de_write(dev_priv, TRANS_VRR_CTL(cpu_transcoder), trans_vrr_ctl);
> +	intel_de_write(dev_priv, TRANS_VRR_CTL(cpu_transcoder), trans_vrr_ctl(crtc_state));
>  	intel_de_write(dev_priv, TRANS_VRR_FLIPLINE(cpu_transcoder), crtc_state->vrr.flipline - 1);
>  	intel_de_write(dev_priv, TRANS_PUSH(cpu_transcoder), TRANS_PUSH_EN);
> +
> +	intel_de_write(dev_priv, TRANS_VRR_CTL(cpu_transcoder),
> +		       VRR_CTL_VRR_ENABLE | trans_vrr_ctl(crtc_state));
>  }
>  
>  void intel_vrr_send_push(const struct intel_crtc_state *crtc_state)
> @@ -222,8 +227,13 @@ void intel_vrr_disable(const struct intel_crtc_state *old_crtc_state)
>  	if (!old_crtc_state->vrr.enable)
>  		return;
>  
> -	intel_de_write(dev_priv, TRANS_VRR_CTL(cpu_transcoder), 0);
> +	intel_de_write(dev_priv, TRANS_VRR_CTL(cpu_transcoder),
> +		       trans_vrr_ctl(old_crtc_state));
> +	intel_de_wait_for_clear(dev_priv, TRANS_VRR_STATUS(cpu_transcoder),
> +				VRR_STATUS_VRR_EN_LIVE, 1000);
> +
>  	intel_de_write(dev_priv, TRANS_PUSH(cpu_transcoder), 0);
> +	intel_de_write(dev_priv, TRANS_VRR_CTL(cpu_transcoder), 0);
>  }
>  
>  void intel_vrr_get_config(struct intel_crtc *crtc,
> -- 
> 2.37.4
>