On 10/7/2025 1:26 AM, Ville Syrjälä wrote:
On Mon, Oct 06, 2025 at 09:58:49AM +0530, Ankit Nautiyal wrote:
As we move towards using a shorter, optimized guardband, we need to adjust
how the delayed vblank start is computed.
Introduce intel_crtc_compute_vrr_guardband() to handle guardband
computation and apply vblank_start adjustment for platforms that always use
the VRR timing generator.
This function wraps the existing intel_vrr_compute_guardband() and adjusts
crtc_vblank_start using (vblank_length - guardband) only when
intel_vrr_always_use_vrr_tg() is true. Since the guardband is not yet
optimized, the adjustment currently evaluates to zero, preserving existing
behavior.
This paves way for guardband optimization, by handling the movement of
the crtc_vblank_start for platforms that have VRR TG always active.
Also update allow_vblank_delay_fastset() to permit vblank delay adjustments
during fastboot when VRR TG is always active, even without inherited state.
Signed-off-by: Ankit Nautiyal <[email protected]>
---
drivers/gpu/drm/i915/display/intel_display.c | 33 ++++++++++++++++++--
1 file changed, 30 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_display.c
b/drivers/gpu/drm/i915/display/intel_display.c
index b2d4e24fd7c6..1964e41b5704 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -2403,6 +2403,27 @@ static int intel_crtc_compute_set_context_latency(struct
intel_atomic_state *sta
return 0;
}
+static void intel_crtc_compute_vrr_guardband(struct intel_atomic_state *state,
+ struct intel_crtc *crtc)
Why this wrapper? You could just stick the adjustemnt into
intel_vrr_compute_guardband().
The idea was to prepare for the optimized guardband which needs
connector also.
In subsequent patch I am getting the connector here to use the optimized
guardband only for platforms with always_use_vrr_tg=true.
And at last I am making changes in intel_vrr_compute_guardband() itself.
As for this patch I can just avoid the wrapper and just use the adjustment.
+{
+ struct intel_display *display = to_intel_display(state);
+ 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;
+
+ intel_vrr_compute_guardband(crtc_state);
+
+ if (intel_vrr_always_use_vrr_tg(display)) {
+ int vblank_length = adjusted_mode->crtc_vtotal -
+ (crtc_state->set_context_latency +
+ adjusted_mode->crtc_vdisplay);
+
+ adjusted_mode->crtc_vblank_start +=
+ vblank_length - crtc_state->vrr.guardband;
Why aren't you using the same 'vblank_start = vtotal-guardband' here as
during readout?
Hmm I was thinking this more as change in the vblank_start. In
compute_set_context_latency we move the vblank_start by SCL lines. Here
we move further as much amount as the change in guardband.
But I guess that is not very intuitive, so I will just set
crtc_vblank_start as vtotal - guardband here.
+ }
+}
+
static int intel_crtc_compute_config(struct intel_atomic_state *state,
struct intel_crtc *crtc)
{
@@ -2414,7 +2435,7 @@ static int intel_crtc_compute_config(struct
intel_atomic_state *state,
if (ret)
return ret;
- intel_vrr_compute_guardband(crtc_state);
+ intel_crtc_compute_vrr_guardband(state, crtc);
ret = intel_dpll_crtc_compute_clock(state, crtc);
if (ret)
@@ -5105,9 +5126,15 @@ static bool allow_vblank_delay_fastset(const struct
intel_crtc_state *old_crtc_s
* 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...
+ *
+ * Also allow this when the VRR timing generator is always on,
+ * which implies optimized guardband is used. In such cases,
+ * vblank delay may vary even without inherited state, but it's
+ * still safe as VRR guardband is still same.
*/
- return HAS_LRR(display) && old_crtc_state->inherited &&
- !intel_crtc_has_type(old_crtc_state, INTEL_OUTPUT_DSI);
+ return HAS_LRR(display) &&
+ (old_crtc_state->inherited || intel_vrr_always_use_vrr_tg(display))
&&
+ !intel_crtc_has_type(old_crtc_state, INTEL_OUTPUT_DSI);
This part doesn't seem directly related to the making crtc_vblank_start
correct. We still use the non-optimzied guardband so crtc_vblank_start
should not be changing during normal runtime operation.
Yes we do not need this at this time, but only when we really start
using optimized guardband.
I can make it as a separate function.
Regards,
Ankit
}
bool
--
2.45.2
