drm_vblank_offdelay can have three different types of values:
< 0 is to be always treated the same as dev->vblank_disable_immediate
= 0 is to be treated as "never disable vblanks"
> 0 is to be treated as disable immediate if kms driver wants it
that way via dev->vblank_disable_immediate. Otherwise it is
a disable timeout in msecs.
This got broken in Linux 3.18+ for the implementation of
drm_vblank_on. If the user specified a value of zero which should
always reenable vblank irqs in this function, a kms driver could
override the users choice by setting vblank_disable_immediate
to true. This patch fixes the regression and keeps the user in
control.
v2: Only reenable vblank if there are clients left or the user
requested to "never disable vblanks" via offdelay 0. Enabling
vblanks even in the "delayed disable" case (offdelay > 0) was
specifically added by Ville in commit cd19e52aee922
("drm: Kick start vblank interrupts at drm_vblank_on()"),
but after discussion it turns out that this was done by accident.
Citing Ville: "I think it just ended up as a mess due to changing
some of the semantics of offdelay<0 vs. offdelay==0 vs.
disable_immediate during the review of the series. So yeah, given
how drm_vblank_put() works now, I'd just make this check for
offdelay==0."
Signed-off-by: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 3.18+
Cc: michel@xxxxxxxxxxx
Cc: vbabka@xxxxxxx
Cc: ville.syrjala@xxxxxxxxxxxxxxx
Cc: daniel.vetter@xxxxxxxx
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: alexander.deucher@xxxxxxx
Cc: christian.koenig@xxxxxxx
---
drivers/gpu/drm/drm_irq.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 055b0fa..8090989 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -1494,8 +1494,7 @@ void drm_vblank_on(struct drm_device *dev, unsigned int pipe)
* re-enable interrupts if there are users left, or the
* user wishes vblank interrupts to be enabled all the time.
*/
- if (atomic_read(&vblank->refcount) != 0 ||
- (!dev->vblank_disable_immediate && drm_vblank_offdelay == 0))
+ if (atomic_read(&vblank->refcount) != 0 || drm_vblank_offdelay == 0)
WARN_ON(drm_vblank_enable(dev, pipe));
spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
}
--
1.9.1
--
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