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drm/i915/display: Add vblank_start adjustment logic for always-on VRR TG

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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. Also update the
pipe_mode->crtc_vblank_start which is derived from
adjusted_mode->crtc_vblank_start in intel_crtc_compute_pipe_mode().

To maintain consistency between the computed and readout paths, update
the readout logic in intel_vrr_get_config() to overwrite crtc_vblank_start
with the same value (vtotal - guardband) on platforms with always-on
VRR TG.

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)
v3: Use adjusted_mode.crtc_vtotal instead of vmin and include the readout
    logic to keep the compute and readout paths in sync. (Ville)
v4: Also set pipe_mode->crtc_vblank_start as its derived from
    adjusted_mode. (Ville)
v5: Add a comment about rationale behind updating
    pipe_mode->crtc_vblank_start. (Ville)

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://lore.kernel.org/r/20251016055415.2101347-10-ankit.k.nautiyal@intel.com
This commit is contained in:
Ankit Nautiyal 2025-10-16 11:24:13 +05:30
parent 8c0cf4fe9b
commit 5cb2cf6aa8
1 changed files with 26 additions and 1 deletions
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27
drivers/gpu/drm/i915/display/intel_vrr.c
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@ -436,7 +436,8 @@ 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;
struct drm_display_mode *pipe_mode = &crtc_state->hw.pipe_mode;
if (!intel_vrr_possible(crtc_state))
return;
@ -444,6 +445,17 @@ 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 =
adjusted_mode->crtc_vtotal - crtc_state->vrr.guardband;
/*
* pipe_mode has already been derived from the
* original adjusted_mode, keep the two in sync.
*/
pipe_mode->crtc_vblank_start =
adjusted_mode->crtc_vblank_start;
}
if (DISPLAY_VER(display) < 13)
crtc_state->vrr.pipeline_full =
intel_vrr_guardband_to_pipeline_full(crtc_state,
@ -821,6 +833,19 @@ void intel_vrr_get_config(struct intel_crtc_state *crtc_state)
*/
if (crtc_state->vrr.enable)
crtc_state->mode_flags |= I915_MODE_FLAG_VRR;
/*
* For platforms that always use the VRR timing generator, we overwrite
* crtc_vblank_start with vtotal - guardband to reflect the delayed
* vblank start. This works for both default and optimized guardband values.
* On other platforms, we keep the original value from
* intel_get_transcoder_timings() and apply adjustments only in VRR-specific
* paths as needed.
*/
if (intel_vrr_always_use_vrr_tg(display))
crtc_state->hw.adjusted_mode.crtc_vblank_start =
crtc_state->hw.adjusted_mode.crtc_vtotal -
crtc_state->vrr.guardband;
}
int intel_vrr_safe_window_start(const struct intel_crtc_state *crtc_state)