Nouveau - Nov 2015 - [PATCH] drm/nouveau: Fix pre-nv50 pageflip events (v2)

From: Daniel Vetter <daniel.vetter at ffwll.ch>

Apparently pre-nv50 pageflip events happen before the actual vblank
period. Therefore that functionality got semi-disabled in

commit af4870e406126b7ac0ae7c7ce5751f25ebe60f28
Author: Mario Kleiner <mario.kleiner.de at gmail.com>
Date:   Tue May 13 00:42:08 2014 +0200

    drm/nouveau/kms/nv04-nv40: fix pageflip events via special case.

Unfortunately that hack got uprooted in

commit cc1ef118fc099295ae6aabbacc8af94d8d8885eb
Author: Thierry Reding <treding at nvidia.com>
Date:   Wed Aug 12 17:00:31 2015 +0200

    drm/irq: Make pipe unsigned and name consistent

Trigering a warning when trying to sample the vblank timestamp for a
non-existing pipe. There's a few ways to fix this:

- Open-code the old behaviour, which just enshrines this slight
  breakage of the userspace ABI.

- Revert Mario's commit and again inflict broken timestamps, again not
  pretty.

- Fix this for real by delaying the pageflip TS until the next vblank
  interrupt, thereby making it accurate.

This patch implements the third option. Since having a page flip
interrupt that happens when the pageflip gets armed and not when it
completes in the next vblank seems to be fairly common (older i915 hw
works very similarly) create a new helper to arm vblank events for
such drivers.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=106431
Cc: Thierry Reding <treding at nvidia.com>
Cc: Mario Kleiner <mario.kleiner.de at gmail.com>
Cc: Ben Skeggs <bskeggs at redhat.com>
Cc: Ilia Mirkin <imirkin at alum.mit.edu>

v2 (mario): Integrate my own review comments into Daniels patch.
   - Fix function prototypes in drmP.h
   - Add missing vblank_put() for pageflip completion without
     pageflip event.
   - Initialize sequence number for queued pageflip event to avoid
     trouble in drm_handle_vblank_events().
   - Remove dead code and spelling fix.

Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
Reviewed-by: Mario Kleiner <mario.kleiner.de at gmail.com>
---
 drivers/gpu/drm/drm_irq.c                 | 54 ++++++++++++++++++++++++++++++-
 drivers/gpu/drm/nouveau/nouveau_display.c | 19 ++++++-----
 include/drm/drmP.h                        |  4 +++
 3 files changed, 68 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index eba6337..819b8c1 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -972,7 +972,8 @@ static void send_vblank_event(struct drm_device *dev,
 		struct drm_pending_vblank_event *e,
 		unsigned long seq, struct timeval *now)
 {
-	WARN_ON_SMP(!spin_is_locked(&dev->event_lock));
+	assert_spin_locked(&dev->event_lock);
+
 	e->event.sequence = seq;
 	e->event.tv_sec = now->tv_sec;
 	e->event.tv_usec = now->tv_usec;
@@ -985,6 +986,57 @@ static void send_vblank_event(struct drm_device *dev,
 }
 
 /**
+ * drm_arm_vblank_event - arm vblank event after pageflip
+ * @dev: DRM device
+ * @pipe: CRTC index
+ * @e: the event to prepare to send
+ *
+ * A lot of drivers need to generate vblank events for the very next vblank
+ * interrupt. For example when the page flip interrupt happens when the page
+ * flip gets armed, but not when it actually executes within the next vblank
+ * period. This helper function implements exactly the required vblank arming
+ * behaviour.
+ *
+ * Caller must hold event lock. Caller must also hold a vblank reference for
the
+ * event @e, which will be dropped when the next vblank arrives.
+ *
+ * This is the legacy version of drm_crtc_arm_vblank_event().
+ */
+void drm_arm_vblank_event(struct drm_device *dev, unsigned int pipe,
+			  struct drm_pending_vblank_event *e)
+{
+	assert_spin_locked(&dev->event_lock);
+
+	e->pipe = pipe;
+	e->event.sequence = drm_vblank_count(dev, pipe);
+	list_add_tail(&e->base.link, &dev->vblank_event_list);
+}
+EXPORT_SYMBOL(drm_arm_vblank_event);
+
+/**
+ * drm_arm_vblank_event - arm vblank event after pageflip
+ * @crtc: the source CRTC of the vblank event
+ * @e: the event to send
+ *
+ * A lot of drivers need to generate vblank events for the very next vblank
+ * interrupt. For example when the page flip interrupt happens when the page
+ * flip gets armed, but not when it actually executes within the next vblank
+ * period. This helper function implements exactly the required vblank arming
+ * behaviour.
+ *
+ * Caller must hold event lock. Caller must also hold a vblank reference for
the
+ * event @e, which will be dropped when the next vblank arrives.
+ *
+ * This is the native KMS version of drm_send_vblank_event().
+ */
+void drm_crtc_arm_vblank_event(struct drm_crtc *crtc,
+			       struct drm_pending_vblank_event *e)
+{
+	drm_arm_vblank_event(crtc->dev, drm_crtc_index(crtc), e);
+}
+EXPORT_SYMBOL(drm_crtc_arm_vblank_event);
+
+/**
  * drm_send_vblank_event - helper to send vblank event after pageflip
  * @dev: DRM device
  * @pipe: CRTC index
diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c
b/drivers/gpu/drm/nouveau/nouveau_display.c
index db6bc67..64c8d93 100644
--- a/drivers/gpu/drm/nouveau/nouveau_display.c
+++ b/drivers/gpu/drm/nouveau/nouveau_display.c
@@ -829,7 +829,6 @@ nouveau_finish_page_flip(struct nouveau_channel *chan,
 	struct drm_device *dev = drm->dev;
 	struct nouveau_page_flip_state *s;
 	unsigned long flags;
-	int crtcid = -1;
 
 	spin_lock_irqsave(&dev->event_lock, flags);
 
@@ -841,15 +840,19 @@ nouveau_finish_page_flip(struct nouveau_channel *chan,
 
 	s = list_first_entry(&fctx->flip, struct nouveau_page_flip_state,
head);
 	if (s->event) {
-		/* Vblank timestamps/counts are only correct on >= NV-50 */
-		if (drm->device.info.family >= NV_DEVICE_INFO_V0_TESLA)
-			crtcid = s->crtc;
+		if (drm->device.info.family < NV_DEVICE_INFO_V0_TESLA) {
+			drm_arm_vblank_event(dev, s->crtc, s->event);
+		} else {
+			drm_send_vblank_event(dev, s->crtc, s->event);
 
-		drm_send_vblank_event(dev, crtcid, s->event);
+			/* Give up ownership of vblank for page-flipped crtc */
+			drm_vblank_put(dev, s->crtc);
+		}
+	}
+	else {
+		/* Give up ownership of vblank for page-flipped crtc */
+		drm_vblank_put(dev, s->crtc);
 	}
-
-	/* Give up ownership of vblank for page-flipped crtc */
-	drm_vblank_put(dev, s->crtc);
 
 	list_del(&s->head);
 	if (ps)
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 4d3b842..02a1512 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -948,6 +948,10 @@ extern void drm_send_vblank_event(struct drm_device *dev,
unsigned int pipe,
 				  struct drm_pending_vblank_event *e);
 extern void drm_crtc_send_vblank_event(struct drm_crtc *crtc,
 				       struct drm_pending_vblank_event *e);
+extern void drm_arm_vblank_event(struct drm_device *dev, unsigned int pipe,
+				 struct drm_pending_vblank_event *e);
+extern void drm_crtc_arm_vblank_event(struct drm_crtc *crtc,
+				      struct drm_pending_vblank_event *e);
 extern bool drm_handle_vblank(struct drm_device *dev, unsigned int pipe);
 extern bool drm_crtc_handle_vblank(struct drm_crtc *crtc);
 extern int drm_vblank_get(struct drm_device *dev, unsigned int pipe);
-- 
1.9.1

On Mon, Nov 9, 2015 at 7:57 AM, Mario Kleiner
<mario.kleiner.de at gmail.com> wrote:
> From: Daniel Vetter <daniel.vetter at ffwll.ch>
>
> Apparently pre-nv50 pageflip events happen before the actual vblank
> period. Therefore that functionality got semi-disabled in
>
> commit af4870e406126b7ac0ae7c7ce5751f25ebe60f28
> Author: Mario Kleiner <mario.kleiner.de at gmail.com>
> Date:   Tue May 13 00:42:08 2014 +0200
>
>     drm/nouveau/kms/nv04-nv40: fix pageflip events via special case.
>
> Unfortunately that hack got uprooted in
>
> commit cc1ef118fc099295ae6aabbacc8af94d8d8885eb
> Author: Thierry Reding <treding at nvidia.com>
> Date:   Wed Aug 12 17:00:31 2015 +0200
>
>     drm/irq: Make pipe unsigned and name consistent
>
> Trigering a warning when trying to sample the vblank timestamp for a
> non-existing pipe. There's a few ways to fix this:
>
> - Open-code the old behaviour, which just enshrines this slight
>   breakage of the userspace ABI.
>
> - Revert Mario's commit and again inflict broken timestamps, again not
>   pretty.
>
> - Fix this for real by delaying the pageflip TS until the next vblank
>   interrupt, thereby making it accurate.
>
> This patch implements the third option. Since having a page flip
> interrupt that happens when the pageflip gets armed and not when it
> completes in the next vblank seems to be fairly common (older i915 hw
> works very similarly) create a new helper to arm vblank events for
> such drivers.
>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=106431
> Cc: Thierry Reding <treding at nvidia.com>
> Cc: Mario Kleiner <mario.kleiner.de at gmail.com>
> Cc: Ben Skeggs <bskeggs at redhat.com>
> Cc: Ilia Mirkin <imirkin at alum.mit.edu>
>
> v2 (mario): Integrate my own review comments into Daniels patch.
>    - Fix function prototypes in drmP.h
>    - Add missing vblank_put() for pageflip completion without
>      pageflip event.
>    - Initialize sequence number for queued pageflip event to avoid
>      trouble in drm_handle_vblank_events().
>    - Remove dead code and spelling fix.
>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> Reviewed-by: Mario Kleiner <mario.kleiner.de at gmail.com>
Without commenting on the actual patch, a few points of procedure:

(a) If you're sending the patch, you're supposed to add your
Signed-off-by. So you'd keep Daniel's and add yours.
(b) Since this is triggering warns for real people in real situations,
tack on a

Cc: stable at vger.kernel.org # v4.3

Cheers,

  -ilia

On 11/09/2015 02:02 PM, Ilia Mirkin wrote:
> On Mon, Nov 9, 2015 at 7:57 AM, Mario Kleiner
> <mario.kleiner.de at gmail.com> wrote:
>> From: Daniel Vetter <daniel.vetter at ffwll.ch>
>>
>> Apparently pre-nv50 pageflip events happen before the actual vblank
>> period. Therefore that functionality got semi-disabled in
>>
>> commit af4870e406126b7ac0ae7c7ce5751f25ebe60f28
>> Author: Mario Kleiner <mario.kleiner.de at gmail.com>
>> Date:   Tue May 13 00:42:08 2014 +0200
>>
>>      drm/nouveau/kms/nv04-nv40: fix pageflip events via special case.
>>
>> Unfortunately that hack got uprooted in
>>
>> commit cc1ef118fc099295ae6aabbacc8af94d8d8885eb
>> Author: Thierry Reding <treding at nvidia.com>
>> Date:   Wed Aug 12 17:00:31 2015 +0200
>>
>>      drm/irq: Make pipe unsigned and name consistent
>>
>> Trigering a warning when trying to sample the vblank timestamp for a
>> non-existing pipe. There's a few ways to fix this:
>>
>> - Open-code the old behaviour, which just enshrines this slight
>>    breakage of the userspace ABI.
>>
>> - Revert Mario's commit and again inflict broken timestamps, again
not
>>    pretty.
>>
>> - Fix this for real by delaying the pageflip TS until the next vblank
>>    interrupt, thereby making it accurate.
>>
>> This patch implements the third option. Since having a page flip
>> interrupt that happens when the pageflip gets armed and not when it
>> completes in the next vblank seems to be fairly common (older i915 hw
>> works very similarly) create a new helper to arm vblank events for
>> such drivers.
>>
>> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=106431
>> Cc: Thierry Reding <treding at nvidia.com>
>> Cc: Mario Kleiner <mario.kleiner.de at gmail.com>
>> Cc: Ben Skeggs <bskeggs at redhat.com>
>> Cc: Ilia Mirkin <imirkin at alum.mit.edu>
>>
>> v2 (mario): Integrate my own review comments into Daniels patch.
>>     - Fix function prototypes in drmP.h
>>     - Add missing vblank_put() for pageflip completion without
>>       pageflip event.
>>     - Initialize sequence number for queued pageflip event to avoid
>>       trouble in drm_handle_vblank_events().
>>     - Remove dead code and spelling fix.
>>
>> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
>> Reviewed-by: Mario Kleiner <mario.kleiner.de at gmail.com>
>
> Without commenting on the actual patch, a few points of procedure:
>
> (a) If you're sending the patch, you're supposed to add your
> Signed-off-by. So you'd keep Daniel's and add yours.
I thought my tiny fixes didn't warrant adding a signed off by myself, 
but if that was wrong, consider it added:

v2: Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com>
> (b) Since this is triggering warns for real people in real situations,
> tack on a
>
> Cc: stable at vger.kernel.org # v4.3
>
Ah, sorry, this is already a problem in a released kernel? I thought 
this was something new and so far only for drm-next.

ciao,
-mario
> Cheers,
>
>    -ilia
>