[PATCH v2 1/5] drm/vblank: Add drm_crtc_vblank_is_off() helper

[<sunpeng.li@amd.com>]

From: Leo Li <sunpeng.li@amd.com>

Add and use an drm internal helper to check if vblanks have been turned
off (via drm_crtc_vblank_off()) for a CRTC, rather than relying on the
return value of drm_crtc_vblank_get().

This is in preparation of introducing deferred vblank enable/disable, as
vblank_get() will not return the expected error code when the driver
defers vblank enable.

No functional change is intended.

Signed-off-by: Leo Li <sunpeng.li@amd.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 11 +++++------
 drivers/gpu/drm/drm_internal.h      |  1 +
 drivers/gpu/drm/drm_vblank.c        | 17 +++++++++++++++++
 3 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 26953ed6b53e8..102937e3ff35b 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -48,6 +48,7 @@
 
 #include "drm_crtc_helper_internal.h"
 #include "drm_crtc_internal.h"
+#include "drm_internal.h"
 
 /**
  * DOC: overview
@@ -1259,7 +1260,7 @@ drm_atomic_helper_commit_crtc_disable(struct drm_device *dev, struct drm_atomic_
 
 	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
 		const struct drm_crtc_helper_funcs *funcs;
-		int ret;
+		bool vblank_off;
 
 		/* Shut down everything that needs a full modeset. */
 		if (!drm_atomic_crtc_needs_modeset(new_crtc_state))
@@ -1287,19 +1288,17 @@ drm_atomic_helper_commit_crtc_disable(struct drm_device *dev, struct drm_atomic_
 		if (!drm_dev_has_vblank(dev))
 			continue;
 
-		ret = drm_crtc_vblank_get(crtc);
+		vblank_off = drm_crtc_vblank_is_off(crtc);
 		/*
 		 * Self-refresh is not a true "disable"; ensure vblank remains
 		 * enabled.
 		 */
 		if (new_crtc_state->self_refresh_active)
-			WARN_ONCE(ret != 0,
+			WARN_ONCE(vblank_off,
 				  "driver disabled vblank in self-refresh\n");
 		else
-			WARN_ONCE(ret != -EINVAL,
+			WARN_ONCE(!vblank_off,
 				  "driver forgot to call drm_crtc_vblank_off()\n");
-		if (ret == 0)
-			drm_crtc_vblank_put(crtc);
 	}
 }
 EXPORT_SYMBOL(drm_atomic_helper_commit_crtc_disable);
diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index f893b1e3a596e..7d10515fe2ed5 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -131,6 +131,7 @@ static inline void drm_vblank_destroy_worker(struct drm_vblank_crtc *vblank)
 int drm_vblank_worker_init(struct drm_vblank_crtc *vblank);
 void drm_vblank_cancel_pending_works(struct drm_vblank_crtc *vblank);
 void drm_handle_vblank_works(struct drm_vblank_crtc *vblank);
+bool drm_crtc_vblank_is_off(struct drm_crtc *crtc);
 
 /* IOCTLS */
 int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index f78bf37f1e0a7..983c131b23694 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -2318,3 +2318,20 @@ void drm_crtc_vblank_get_vblank_timeout(struct drm_crtc *crtc, ktime_t *vblank_t
 	*vblank_time = ktime_sub(*vblank_time, vtimer->interval);
 }
 EXPORT_SYMBOL(drm_crtc_vblank_get_vblank_timeout);
+
+/**
+ * drm_crtc_vblank_is_off - check if vblank is off on a CRTC
+ * @crtc: CRTC in question
+ *
+ * Return true if vblanks is currently turned off via drm_crtc_vblank_off().
+ * Return False otherwise.
+ */
+bool drm_crtc_vblank_is_off(struct drm_crtc *crtc)
+{
+	struct drm_vblank_crtc *vblank = drm_crtc_vblank_crtc(crtc);
+
+	/* Spinlock adds the necessary barriers */
+	guard(spinlock_irqsave)(&crtc->dev->vbl_lock);
+	return vblank->inmodeset && !vblank->enabled;
+}
+EXPORT_SYMBOL(drm_crtc_vblank_is_off);
-- 
2.53.0