On 9/29/2025 2:30 PM, Ville Syrjälä wrote:
On Sun, Sep 28, 2025 at 12:35:40PM +0530, Ankit Nautiyal wrote:
As we move towards using a shorter, optimized guardband, we need to adjust
how the delayed vblank start is computed.
Use the helper intel_vrr_compute_guardband() to calculate the optimized
guardband. Since this is measured from the vblank end, we shift the
vblank-start accordingly.
Calculate the minimum delay required based on the guardband and apply it in
intel_crtc_vblank_delay() to update crtc_vblank_start.
Additionally, introduce a new allow_vblank_delay_fastset() helper that
combines the existing LRR-based logic with an additional check for the
optimized guardband usage.
v2:
- Check if optimized guardband is more than vblank length and add debug
print.
- Extend vblank delay fastset logic to cover optimized guardband.
Signed-off-by: Ankit Nautiyal <[email protected]>
---
drivers/gpu/drm/i915/display/intel_display.c | 79 +++++++++++++++++++-
1 file changed, 76 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_display.c
b/drivers/gpu/drm/i915/display/intel_display.c
index 4135f9be53fd..97a3121a204f 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -2361,6 +2361,67 @@ static int intel_crtc_compute_pipe_mode(struct
intel_crtc_state *crtc_state)
return 0;
}
+static
+int intel_crtc_min_guardband_delay(struct intel_atomic_state *state,
+ struct intel_crtc *crtc)
+{
+ struct intel_display *display = to_intel_display(state);
+ struct intel_crtc_state *crtc_state =
+ intel_atomic_get_new_crtc_state(state, crtc);
+ const struct drm_display_mode *adjusted_mode =
+ &crtc_state->hw.adjusted_mode;
+ struct drm_connector_state *conn_state;
+ struct drm_connector *drm_connector;
+ int vblank_length;
+ int i;
+
+ if (!intel_vrr_use_optimized_guardband(crtc_state))
+ return 0;
+
+ vblank_length = crtc_state->vrr.vmin -
+ adjusted_mode->crtc_vdisplay;
+
+ for_each_new_connector_in_state(&state->base,
+ drm_connector,
+ conn_state, i) {
+ int guardband;
+ struct intel_connector *connector;
+
+ if (conn_state->crtc != &crtc->base)
+ continue;
+
+ connector = to_intel_connector(drm_connector);
+ guardband = intel_vrr_compute_guardband(crtc_state,
+ connector);
+ if (guardband > vblank_length) {
+ drm_dbg_kms(display->drm,
+ "[CRTC:%d:%s] Cannot optimize guardband (%d)
exceeds max (%d)\n",
+ crtc->base.base.id, crtc->base.name,
+ guardband,
+ vblank_length);
+ return 0;
+ }
+
+ return vblank_length - guardband;
+ }
+
+ return 0;
+}
+
+static void intel_crtc_vblank_delay(struct intel_atomic_state *state,
+ struct intel_crtc *crtc)
+{
+ struct intel_crtc_state *crtc_state =
+ intel_atomic_get_new_crtc_state(state, crtc);
+ struct drm_display_mode *adjusted_mode =
+ &crtc_state->hw.adjusted_mode;
+ int vblank_delay = 0;
+
+ vblank_delay = intel_crtc_min_guardband_delay(state, crtc);
+
+ adjusted_mode->crtc_vblank_start += vblank_delay;
+}
+
static int intel_crtc_set_context_latency(struct intel_crtc_state *crtc_state)
{
struct intel_display *display = to_intel_display(crtc_state);
@@ -2413,6 +2474,7 @@ static int intel_crtc_compute_config(struct
intel_atomic_state *state,
ret = intel_crtc_compute_set_context_latency(state, crtc);
if (ret)
return ret;
+ intel_crtc_vblank_delay(state, crtc);
IMO we should get rid of all this vblank_delay terminology here.
This one I think should just be our current
intel_vrr_compute_config_late() (renamed to eg.
intel_vrr_compute_guardband()).
Hmm ok so will rename this and call from intel_modeset_pipe_config_late().
Regards,
Ankit
After which we just have to solve all the chicken vs. egg problems
to really compute the approriate optimized guardband value.
ret = intel_dpll_crtc_compute_clock(state, crtc);
if (ret)
@@ -5101,13 +5163,24 @@ static bool allow_vblank_delay_fastset_lrr(const struct
intel_crtc_state *old_cr
{
struct intel_display *display = to_intel_display(old_crtc_state);
+ return HAS_LRR(display) && old_crtc_state->inherited &&
+ !intel_crtc_has_type(old_crtc_state, INTEL_OUTPUT_DSI);
+}
+
+static bool allow_vblank_delay_fastset(const struct intel_crtc_state
*old_crtc_state,
+ const struct intel_crtc_state
*new_crtc_state)
+{
/*
* Allow fastboot to fix up vblank delay (handled via LRR
* codepaths), a bit dodgy as the registers aren't
* double buffered but seems to be working more or less...
+ *
+ * Additionally, with the optimized guardband the vblank start
+ * is moved further away from the undelayed vblank. Allow this
+ * vblank delay when optimized guardband is used.
*/
- return HAS_LRR(display) && old_crtc_state->inherited &&
- !intel_crtc_has_type(old_crtc_state, INTEL_OUTPUT_DSI);
+ return allow_vblank_delay_fastset_lrr(old_crtc_state) ||
+ intel_vrr_use_optimized_guardband(new_crtc_state);
}
bool
@@ -5242,7 +5315,7 @@ intel_pipe_config_compare(const struct intel_crtc_state
*current_config,
PIPE_CONF_CHECK_I(name.crtc_hsync_start); \
PIPE_CONF_CHECK_I(name.crtc_hsync_end); \
PIPE_CONF_CHECK_I(name.crtc_vdisplay); \
- if (!fastset || !allow_vblank_delay_fastset_lrr(current_config)) \
+ if (!fastset || !allow_vblank_delay_fastset(current_config,
pipe_config)) \
PIPE_CONF_CHECK_I(name.crtc_vblank_start); \
PIPE_CONF_CHECK_I(name.crtc_vsync_start); \
PIPE_CONF_CHECK_I(name.crtc_vsync_end); \
--
2.45.2
