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* Re: [PATCH v4 1/2] drm: Introduce drm_crtc_vblank_prepare()
@ 2026-01-29  4:43 Derek John Clark
  2026-01-29 15:15 ` Leo Li
  0 siblings, 1 reply; 6+ messages in thread
From: Derek John Clark @ 2026-01-29  4:43 UTC (permalink / raw)
  To: sunpeng.li
  Cc: Harry.Wentland, airlied, amd-gfx, dri-devel, jani.nikula, simona,
	Mario Limonciello, ville.syrjala

>From: Leo Li <sunpeng.li@amd.com>
>
>Some drivers need to perform sleepable operations prior to enabling
>vblank interrupts. A display hardware spin-up from a low-power state
>that requires synchronization with the rest of the driver, for example.
>
>To support this, introduce a DRM-internal drm_crtc_vblank_prepare()
>helper that calls back into the driver -- if implemented -- for DRM to
>do such preparation work before enabling vblank.
>
>v3:
>* Unexport drm_crtc_vblank_prepare() and make it DRM internal
>* Drop warnings in drm core for vblank_prepare(), drivers can do so in
>  their implementations
>* Drop unnecessary crtc null checks
>* Check for drm_dev_has_vblank()
>* Rebase on latest drm-misc-next
>
>v4:
>* EXPORT function to fix build error on DRM_KMS_HELPER=m
>
>Signed-off-by: Leo Li <sunpeng.li@amd.com>

Hi Leo.

I wanted to know what branch this series applies to. I'm trying to
troubleshoot a possible vblank issue on the Legion Go 2 and was
pointed towards this patch series. Unfortunately I can't get it to
apply cleanly to drm/drm-fixes, drm/drm-next or stable/linux-6.18.y


From commit 15392f76405ecb953216b437bed76ffa49cefb7b (HEAD,
drm/drm-next, drm/HEAD):
$ b4 shazam https://lore.kernel.org/dri-devel/20260127194143.176248-1-sunpeng.li@amd.com/
Grabbing thread from
lore.kernel.org/all/20260127194143.176248-1-sunpeng.li@amd.com/t.mbox.gz
Checking for newer revisions
Grabbing search results from lore.kernel.org
Analyzing 2 messages in the thread
Analyzing 0 code-review messages
Checking attestation on all messages, may take a moment...
---
  [PATCH v4 1/2] drm: Introduce drm_crtc_vblank_prepare()
  [PATCH v4 2/2] drm/amd/display: Implement prepare_vblank_enable callback
  ---
  NOTE: install dkimpy for DKIM signature verification
---
Total patches: 2
---
Applying: drm: Introduce drm_crtc_vblank_prepare()
Applying: drm/amd/display: Implement prepare_vblank_enable callback
Patch failed at 0002 drm/amd/display: Implement prepare_vblank_enable callback
error: patch failed: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c:277
error: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c: patch
does not apply


Thanks,
Derek

^ permalink raw reply	[flat|nested] 6+ messages in thread
* [PATCH v4 1/2] drm: Introduce drm_crtc_vblank_prepare()
@ 2026-01-27 19:41 sunpeng.li
  0 siblings, 0 replies; 6+ messages in thread
From: sunpeng.li @ 2026-01-27 19:41 UTC (permalink / raw)
  To: amd-gfx, dri-devel
  Cc: Harry.Wentland, simona, airlied, jani.nikula, ville.syrjala,
	superm1, Leo Li

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

Some drivers need to perform sleepable operations prior to enabling
vblank interrupts. A display hardware spin-up from a low-power state
that requires synchronization with the rest of the driver, for example.

To support this, introduce a DRM-internal drm_crtc_vblank_prepare()
helper that calls back into the driver -- if implemented -- for DRM to
do such preparation work before enabling vblank.

v3:
* Unexport drm_crtc_vblank_prepare() and make it DRM internal
* Drop warnings in drm core for vblank_prepare(), drivers can do so in
  their implementations
* Drop unnecessary crtc null checks
* Check for drm_dev_has_vblank()
* Rebase on latest drm-misc-next

v4:
* EXPORT function to fix build error on DRM_KMS_HELPER=m

Signed-off-by: Leo Li <sunpeng.li@amd.com>
---
 drivers/gpu/drm/drm_atomic_helper.c  |  9 +++++
 drivers/gpu/drm/drm_client_modeset.c |  4 +++
 drivers/gpu/drm/drm_internal.h       |  1 +
 drivers/gpu/drm/drm_plane.c          |  5 +++
 drivers/gpu/drm/drm_vblank.c         | 49 ++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_vblank_helper.c  |  5 ++-
 drivers/gpu/drm/drm_vblank_work.c    |  8 +++++
 include/drm/drm_crtc.h               | 21 ++++++++++++
 8 files changed, 101 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 5840e9cc6f666..2b9fa4aa48a1a 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
@@ -1268,6 +1269,10 @@ crtc_disable(struct drm_device *dev, struct drm_atomic_state *state)
 		if (!drm_dev_has_vblank(dev))
 			continue;
 
+		ret = drm_crtc_vblank_prepare(crtc);
+		if (ret)
+			continue;
+
 		ret = drm_crtc_vblank_get(crtc);
 		/*
 		 * Self-refresh is not a true "disable"; ensure vblank remains
@@ -1823,6 +1828,10 @@ drm_atomic_helper_wait_for_vblanks(struct drm_device *dev,
 		if (!new_crtc_state->active)
 			continue;
 
+		ret = drm_crtc_vblank_prepare(crtc);
+		if (ret != 0)
+			continue;
+
 		ret = drm_crtc_vblank_get(crtc);
 		if (ret != 0)
 			continue;
diff --git a/drivers/gpu/drm/drm_client_modeset.c b/drivers/gpu/drm/drm_client_modeset.c
index fc4caf7da5fcd..6ccbde921dde4 100644
--- a/drivers/gpu/drm/drm_client_modeset.c
+++ b/drivers/gpu/drm/drm_client_modeset.c
@@ -1325,6 +1325,10 @@ int drm_client_modeset_wait_for_vblank(struct drm_client_dev *client, unsigned i
 	 * Only wait for a vblank event if the CRTC is enabled, otherwise
 	 * just don't do anything, not even report an error.
 	 */
+	ret = drm_crtc_vblank_prepare(crtc);
+	if (ret)
+		return ret;
+
 	ret = drm_crtc_vblank_get(crtc);
 	if (!ret) {
 		drm_crtc_wait_one_vblank(crtc);
diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index f893b1e3a596e..8e3e21d734075 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -112,6 +112,7 @@ static inline bool drm_vblank_passed(u64 seq, u64 ref)
 }
 
 void drm_vblank_disable_and_save(struct drm_device *dev, unsigned int pipe);
+int drm_crtc_vblank_prepare(struct drm_crtc *crtc);
 int drm_vblank_get(struct drm_device *dev, unsigned int pipe);
 void drm_vblank_put(struct drm_device *dev, unsigned int pipe);
 u64 drm_vblank_count(struct drm_device *dev, unsigned int pipe);
diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
index bed2562bf911b..41681a3d96b15 100644
--- a/drivers/gpu/drm/drm_plane.c
+++ b/drivers/gpu/drm/drm_plane.c
@@ -35,6 +35,7 @@
 #include <drm/drm_vblank.h>
 
 #include "drm_crtc_internal.h"
+#include "drm_internal.h"
 
 /**
  * DOC: overview
@@ -1421,6 +1422,10 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
 		u32 current_vblank;
 		int r;
 
+		r = drm_crtc_vblank_prepare(crtc);
+		if (r)
+			return r;
+
 		r = drm_crtc_vblank_get(crtc);
 		if (r)
 			return r;
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 42fe11cc139b9..f57de47438f0c 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -1208,6 +1208,33 @@ static int drm_vblank_enable(struct drm_device *dev, unsigned int pipe)
 	return ret;
 }
 
+/**
+ * drm_crtc_vblank_prepare - prepare to enable vblank interrupts
+ *
+ * @crtc: which CRTC to prepare
+ *
+ * Some drivers may need to spin-up hardware from a low power state before
+ * enabling vblank interrupts. This function calls the prepare_enable_vblank
+ * callback, if available, to allow drivers to do that.
+ *
+ * This is a DRM-internal function, and is a thin wrapper around a driver
+ * callback. Drivers are expected to sequence their own prepare work internally.
+ *
+ * The spin-up may call sleeping functions, such as mutex_lock(). Therefore,
+ * this must be called from process context, where sleeping is allowed.
+ */
+int drm_crtc_vblank_prepare(struct drm_crtc *crtc)
+{
+	if (!drm_dev_has_vblank(crtc->dev))
+		return -EINVAL;
+
+	if (crtc->funcs->prepare_enable_vblank)
+		return crtc->funcs->prepare_enable_vblank(crtc);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_crtc_vblank_prepare);
+
 int drm_vblank_get(struct drm_device *dev, unsigned int pipe)
 {
 	struct drm_vblank_crtc *vblank = drm_vblank_crtc(dev, pipe);
@@ -1306,6 +1333,10 @@ int drm_crtc_wait_one_vblank(struct drm_crtc *crtc)
 	int ret;
 	u64 last;
 
+	ret = drm_crtc_vblank_prepare(crtc);
+	if (ret)
+		return ret;
+
 	ret = drm_vblank_get(dev, pipe);
 	if (drm_WARN(dev, ret, "vblank not available on crtc %i, ret=%i\n",
 		     pipe, ret))
@@ -1489,6 +1520,9 @@ void drm_crtc_vblank_on_config(struct drm_crtc *crtc,
 	if (drm_WARN_ON(dev, pipe >= dev->num_crtcs))
 		return;
 
+	if (drm_crtc_vblank_prepare(crtc))
+		return;
+
 	spin_lock_irq(&dev->vbl_lock);
 	drm_dbg_vbl(dev, "crtc %d, vblank enabled %d, inmodeset %d\n",
 		    pipe, vblank->enabled, vblank->inmodeset);
@@ -1796,6 +1830,13 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
 		return 0;
 	}
 
+	crtc = drm_crtc_from_index(dev, vblank->pipe);
+	if (crtc) {
+		ret = drm_crtc_vblank_prepare(crtc);
+		if (ret)
+			return ret;
+	}
+
 	ret = drm_vblank_get(dev, pipe);
 	if (ret) {
 		drm_dbg_core(dev,
@@ -2031,6 +2072,10 @@ int drm_crtc_get_sequence_ioctl(struct drm_device *dev, void *data,
 		READ_ONCE(vblank->enabled);
 
 	if (!vblank_enabled) {
+		ret = drm_crtc_vblank_prepare(crtc);
+		if (ret)
+			return ret;
+
 		ret = drm_crtc_vblank_get(crtc);
 		if (ret) {
 			drm_dbg_core(dev,
@@ -2098,6 +2143,10 @@ int drm_crtc_queue_sequence_ioctl(struct drm_device *dev, void *data,
 	if (e == NULL)
 		return -ENOMEM;
 
+	ret = drm_crtc_vblank_prepare(crtc);
+	if (ret)
+		return ret;
+
 	ret = drm_crtc_vblank_get(crtc);
 	if (ret) {
 		drm_dbg_core(dev,
diff --git a/drivers/gpu/drm/drm_vblank_helper.c b/drivers/gpu/drm/drm_vblank_helper.c
index a04a6ba1b0ca0..fc5915acfa7f3 100644
--- a/drivers/gpu/drm/drm_vblank_helper.c
+++ b/drivers/gpu/drm/drm_vblank_helper.c
@@ -8,6 +8,8 @@
 #include <drm/drm_vblank.h>
 #include <drm/drm_vblank_helper.h>
 
+#include "drm_internal.h"
+
 /**
  * DOC: overview
  *
@@ -61,7 +63,8 @@ void drm_crtc_vblank_atomic_flush(struct drm_crtc *crtc,
 	crtc_state->event = NULL;
 
 	if (event) {
-		if (drm_crtc_vblank_get(crtc) == 0)
+		if (drm_crtc_vblank_prepare(crtc) == 0 &&
+		    drm_crtc_vblank_get(crtc) == 0)
 			drm_crtc_arm_vblank_event(crtc, event);
 		else
 			drm_crtc_send_vblank_event(crtc, event);
diff --git a/drivers/gpu/drm/drm_vblank_work.c b/drivers/gpu/drm/drm_vblank_work.c
index 70f0199251ea0..252f60007781b 100644
--- a/drivers/gpu/drm/drm_vblank_work.c
+++ b/drivers/gpu/drm/drm_vblank_work.c
@@ -113,11 +113,19 @@ int drm_vblank_work_schedule(struct drm_vblank_work *work,
 {
 	struct drm_vblank_crtc *vblank = work->vblank;
 	struct drm_device *dev = vblank->dev;
+	struct drm_crtc *crtc;
 	u64 cur_vbl;
 	unsigned long irqflags;
 	bool passed, inmodeset, rescheduling = false, wake = false;
 	int ret = 0;
 
+	crtc = drm_crtc_from_index(dev, vblank->pipe);
+	if (crtc) {
+		ret = drm_crtc_vblank_prepare(crtc);
+		if (ret)
+			return ret;
+	}
+
 	spin_lock_irqsave(&dev->event_lock, irqflags);
 	if (work->cancelling)
 		goto out;
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 66278ffeebd68..e5cf232d604c9 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -871,6 +871,27 @@ struct drm_crtc_funcs {
 	 */
 	u32 (*get_vblank_counter)(struct drm_crtc *crtc);
 
+	/**
+	 * @prepare_enable_vblank:
+	 *
+	 * An optional callback to prepare driver for enabling of vblank
+	 * interrupts. It allows drivers to perform any blocking operations for
+	 * hardware setup that might be needed, and thus is called before any
+	 * vblank spinlocks are acquired. It is called unconditionally,
+	 * regardless of whether vblank interrupts are already enabled or not.
+	 *
+	 * Consequently, this callback is not synchronized with the rest of
+	 * vblank management. Drivers should not access spinlock protected
+	 * states here.
+	 *
+	 * This callback is optional. If not set, no preparation is performed.
+	 *
+	 * Returns:
+	 *
+	 * Zero on success, negative errno on failure.
+	 */
+	int (*prepare_enable_vblank)(struct drm_crtc *crtc);
+
 	/**
 	 * @enable_vblank:
 	 *
-- 
2.52.0


^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2026-01-30  9:06 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2026-01-29  4:43 [PATCH v4 1/2] drm: Introduce drm_crtc_vblank_prepare() Derek John Clark
2026-01-29 15:15 ` Leo Li
2026-01-29 16:40   ` Leo Li
2026-01-29 16:41     ` Derek John Clark
2026-01-29 16:44     ` Mario Limonciello
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2026-01-27 19:41 sunpeng.li

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