Re: [PATCH 7/8] drm/i915/display: Add vblank_start adjustment logic for always-on VRR TG

["Nautiyal, Ankit K" <ankit.k.nautiyal@intel.com>]

On 10/10/2025 8:35 PM, Ville Syrjälä wrote:
> On Thu, Oct 09, 2025 at 02:31:01PM +0530, Ankit Nautiyal wrote:
>> As we move towards using a shorter, optimized guardband, we need to adjust
>> how the delayed vblank start is computed.
>>
>> Adjust the crtc_vblank_start using Vmin Vtotal - guardband only when
>> intel_vrr_always_use_vrr_tg() is true.
>>
>> This also paves way for guardband optimization, by handling the movement of
>> the crtc_vblank_start for platforms that have VRR TG always active.
>>
>> v2: Drop the helper and add the adjustment directly to
>> intel_vrr_compute_guardband(). Ville
>>
>> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
>> ---
>>   drivers/gpu/drm/i915/display/intel_vrr.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
>> index 221b25832e56..5f9b8e5c48be 100644
>> --- a/drivers/gpu/drm/i915/display/intel_vrr.c
>> +++ b/drivers/gpu/drm/i915/display/intel_vrr.c
>> @@ -436,7 +436,7 @@ intel_vrr_max_guardband(struct intel_crtc_state *crtc_state)
>>   void intel_vrr_compute_guardband(struct intel_crtc_state *crtc_state)
>>   {
>>   	struct intel_display *display = to_intel_display(crtc_state);
>> -	const struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
>> +	struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
>>   
>>   	if (!intel_vrr_possible(crtc_state))
>>   		return;
>> @@ -444,6 +444,10 @@ void intel_vrr_compute_guardband(struct intel_crtc_state *crtc_state)
>>   	crtc_state->vrr.guardband = min(crtc_state->vrr.vmin - adjusted_mode->crtc_vdisplay,
>>   					intel_vrr_max_guardband(crtc_state));
>>   
>> +	if (intel_vrr_always_use_vrr_tg(display))
>> +		adjusted_mode->crtc_vblank_start  =
>> +			crtc_state->vrr.vmin - crtc_state->vrr.guardband;
> Since this is for the fixed refresh rate timings I think we should use
> adjusted_mode.crtc_vtotal here instead of vmin (yes the two should be
> equivalent at least for now, but I think it's better to be consistent).

Got it.


>
> And this should be squashed with the readout equivalent to make sure
> both sides stay in sync so there's no possibility of angering the state
> checker by only having the changes on one side.

Right sure, I will merge the two patches.

Regards,

Ankit

>
>> +
>>   	if (DISPLAY_VER(display) < 13)
>>   		crtc_state->vrr.pipeline_full =
>>   			intel_vrr_guardband_to_pipeline_full(crtc_state,
>> -- 
>> 2.45.2