Re: [PATCH v6 2/9] drm/i915/vrr: Restrict CMRR enable condition to VRR-TG-default platforms

On 7/22/2026 10:09 AM, Mitul Golani wrote:
> CMRR is reported as supported from DISPLAY_VER >= 20 (HAS_CMRR), but it
> is built on top of the VRR timing generator running as the default
> timing generator, for now this only happens from DISPLAY_VER >= 30.
> Gate the CMRR enable condition (and its readout) on both,
> so CMRR is only ever enabled on platforms where the VRR timing
> generator is the default.
> 
> This is a preparation patch for the upcoming CMRR enable sequence: CMRR
> remains disabled for now (the "avoid CMRR" short-circuit above is kept),
> and this only refines the condition so that when the enable sequence
> lands, CMRR is correctly restricted to VRR-TG-default platforms. This is
> in line with the comment above, which keeps CMRR disabled until VRR with
> fixed timings is working.
> 
> No functional change.

nit: commit message is quite of obfuscated, can be simpler.

> 
> --v2:
> - Create a separate function to check if CMRR possible
> 
> Signed-off-by: Mitul Golani <[email protected]>
> ---
>   drivers/gpu/drm/i915/display/intel_vrr.c | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
> index 51e4f3309b8b..14f8ac07c911 100644
> --- a/drivers/gpu/drm/i915/display/intel_vrr.c
> +++ b/drivers/gpu/drm/i915/display/intel_vrr.c
> @@ -187,15 +187,21 @@ int intel_vrr_vmax_vblank_start(const struct intel_crtc_state *crtc_state)
>   	return intel_vrr_vmax_vtotal(crtc_state) - crtc_state->vrr.guardband;
>   }
>   
> +static bool intel_vrr_cmrr_possible(const struct intel_crtc_state *crtc_state)
> +{
> +	struct intel_display *display = to_intel_display(crtc_state);
> +
> +	return (HAS_CMRR(display) && intel_vrr_always_use_vrr_tg(display));

redundant outer parenthesis.

With these,

Reviewed-by: Chaitanya Kumar Borah <[email protected]>

> +}
> +
>   static bool
>   is_cmrr_frac_required(struct intel_crtc_state *crtc_state)
>   {
> -	struct intel_display *display = to_intel_display(crtc_state);
>   	int calculated_refresh_k, actual_refresh_k, pixel_clock_per_line;
>   	struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
>   
>   	/* Avoid CMRR for now till we have VRR with fixed timings working */
> -	if (!HAS_CMRR(display) || true)
> +	if (!intel_vrr_cmrr_possible(crtc_state) || true)
>   		return false;
>   
>   	actual_refresh_k =
> @@ -1066,7 +1072,7 @@ void intel_vrr_get_config(struct intel_crtc_state *crtc_state)
>   	trans_vrr_ctl = intel_de_read(display,
>   				      TRANS_VRR_CTL(display, cpu_transcoder));
>   
> -	if (HAS_CMRR(display))
> +	if (intel_vrr_cmrr_possible(crtc_state))
>   		crtc_state->cmrr.enable = (trans_vrr_ctl & VRR_CTL_CMRR_ENABLE);
>   
>   	if (crtc_state->cmrr.enable) {