drm/i915/vrr: Check that the push send bit is clear after delayed vblank

Since we don't do mailbox updates the push send bit
should alwyas clear by the time the delay vblank fires
and the flip completes. Check for that to make sure we
haven't screwed up the sequencing/vblank evasion/etc.

On the DSB path we should be able to guarantee this
since we don't have to deal with any scheduler latencies
and whatnot. I suppose unexpected DMA/memory latencies
might be the only thing that might trip us up here.

For the MMIO path we do always have a non-zero chance
that vblank evasion fails (since we can't really guarantee
anything about the scheduling behaviour). That could trip
up this check, but that seems fine since we already print
errors for other types of vblank evasion failures.

Should the CPU vblank evasion actually fail, then the push
send bit can still be set when the next commit happens. But
both the DSB and MMIO paths should handle that situation
gracefully.

v2: Only check once instead of polling for two scanlines
    since we should now be guaranteed to be past the
    delayed vblank.
    Also check in the MMIO path for good measure
v3: Skip the push send check when VRR is disabled.
    With joiner the secondary pipe's DSBs doen't have access
    to the transcoder registers, and so doing this check
    there triggers a reponse timeout error on the DSB. VRR
    is not currently allowed when using joiner, so this will
    prevent the bogus register access.

Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250210160711.24010-1-ville.syrjala@linux.intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_color.c b/drivers/gpu/drm/i915/display/intel_color.c
index 4d8f6509cac4e38aa107bbed005d6e49bf2813bb..cfe14162231dbf78322e018d30cbd74fd60bf204 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_color.c
+++ b/drivers/gpu/drm/i915/display/intel_color.c
@@ -1991,6 +1991,7 @@ void intel_color_prepare_commit(struct intel_atomic_state *state,
        if (crtc_state->use_dsb) {
                intel_vrr_send_push(crtc_state->dsb_color_vblank, crtc_state);
                intel_dsb_wait_vblank_delay(state, crtc_state->dsb_color_vblank);
+               intel_vrr_check_push_sent(crtc_state->dsb_color_vblank, crtc_state);
                intel_dsb_interrupt(crtc_state->dsb_color_vblank);
        }
 

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 9bb1bfe18aeef744dc2575121e7a180a2dcbf346..50c91a6142fd4590beca9ca071545307bac2d8c4 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -7748,6 +7748,7 @@ static void intel_atomic_dsb_finish(struct intel_atomic_state *state,
 
                        intel_vrr_send_push(new_crtc_state->dsb_commit, new_crtc_state);
                        intel_dsb_wait_vblank_delay(state, new_crtc_state->dsb_commit);
+                       intel_vrr_check_push_sent(new_crtc_state->dsb_commit, new_crtc_state);
                        intel_dsb_interrupt(new_crtc_state->dsb_commit);
                }
        }
@@ -7898,6 +7899,9 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
                        intel_crtc_disable_flip_done(state, crtc);
 
                intel_atomic_dsb_wait_commit(new_crtc_state);
+
+               if (!state->base.legacy_cursor_update && !new_crtc_state->use_dsb)
+                       intel_vrr_check_push_sent(NULL, new_crtc_state);
        }
 
        /*

diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
index adb51609d0a316a7336ee3cc62b4960e06ce893b..cac49319026da959af10fa5663a74b247d14afda 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_vrr.c
+++ b/drivers/gpu/drm/i915/display/intel_vrr.c
@@ -416,6 +416,40 @@ void intel_vrr_send_push(struct intel_dsb *dsb,
                intel_dsb_nonpost_end(dsb);
 }
 
+void intel_vrr_check_push_sent(struct intel_dsb *dsb,
+                              const struct intel_crtc_state *crtc_state)
+{
+       struct intel_display *display = to_intel_display(crtc_state);
+       struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
+       enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
+
+       if (!crtc_state->vrr.enable)
+               return;
+
+       /*
+        * Make sure the push send bit has cleared. This should
+        * already be the case as long as the caller makes sure
+        * this is called after the delayed vblank has occurred.
+        */
+       if (dsb) {
+               int wait_us, count;
+
+               wait_us = 2;
+               count = 1;
+
+               /*
+                * If the bit hasn't cleared the DSB will
+                * raise the poll error interrupt.
+                */
+               intel_dsb_poll(dsb, TRANS_PUSH(display, cpu_transcoder),
+                              TRANS_PUSH_SEND, 0, wait_us, count);
+       } else {
+               if (intel_vrr_is_push_sent(crtc_state))
+                       drm_err(display->drm, "[CRTC:%d:%s] VRR push send still pending\n",
+                               crtc->base.base.id, crtc->base.name);
+       }
+}
+
 bool intel_vrr_is_push_sent(const struct intel_crtc_state *crtc_state)
 {
        struct intel_display *display = to_intel_display(crtc_state);

diff --git a/drivers/gpu/drm/i915/display/intel_vrr.h b/drivers/gpu/drm/i915/display/intel_vrr.h
index 899cbf40f880cd844babc8743a56b6d2cbd99200..514822577e8a18d42aba5b01db23b60fed6125f7 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_vrr.h
+++ b/drivers/gpu/drm/i915/display/intel_vrr.h
@@ -25,6 +25,8 @@ void intel_vrr_set_transcoder_timings(const struct intel_crtc_state *crtc_state)
 void intel_vrr_enable(const struct intel_crtc_state *crtc_state);
 void intel_vrr_send_push(struct intel_dsb *dsb,
                         const struct intel_crtc_state *crtc_state);
+void intel_vrr_check_push_sent(struct intel_dsb *dsb,
+                              const struct intel_crtc_state *crtc_state);
 bool intel_vrr_is_push_sent(const struct intel_crtc_state *crtc_state);
 void intel_vrr_disable(const struct intel_crtc_state *old_crtc_state);
 void intel_vrr_get_config(struct intel_crtc_state *crtc_state);