On Mon, 2009-02-16 at 10:55 -0800, Jesse Barnes wrote:
> On Sunday, February 15, 2009 4:02 pm Chris Wilson wrote:
> > On my i915, the flip never occurs and we wait forever on the the vblank.
> > So I presume the command we sent the chip is invalid, or we miss the
> > irq? (I double-checked with lockdep in case I had missed an obvious
> > dead-lock.) Comments on the patch itself inline.
>
> Thanks a lot for looking at this and testing.
>
> Hm, maybe you're not getting vblank interrupts at all? Do you see the count
> increasing? Is the IRQ registered?
Apparently, the vblank is never being enabled... Adding a BUG_ON() to
drm_vblank_put() soon identified the unbalanced culprit. So it appears
that drm_vblank_pre_modeset() can fail to enable vblank, obviously
because at that point we have never enabled vblank in pipeconf - but we
unconditionally decrement the vblank reference counter afterwards. Ok,
so now I see lots of vblank interrupts but the display is still snafu.
The following patch is a crude fix.
>From 1c4fa54654a604e0ea604553b983dca737a76e99 Mon Sep 17 00:00:00 2001
From: Chris Wilson <ch...@chris-wilson.co.uk>
Date: Thu, 19 Feb 2009 14:48:22 +0000
Subject: [PATCH] drm: Correct unbalanced drm_vblank_put() during mode
setting.
The first time we install a mode, the vblank will be disabled for a pipe
and so drm_vblank_get() in drm_vblank_pre_modeset() will fail. As we
unconditionally call drm_vblank_put() afterwards, the vblank reference
counter becomes unbalanced.
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
drivers/gpu/drm/drm_irq.c | 14 ++++++++++----
1 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 3795dbc..93e677a 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -435,6 +435,8 @@ EXPORT_SYMBOL(drm_vblank_get);
*/
void drm_vblank_put(struct drm_device *dev, int crtc)
{
+ BUG_ON (atomic_read (&dev->vblank_refcount[crtc]) == 0);
+
/* Last user schedules interrupt disable */
if (atomic_dec_and_test(&dev->vblank_refcount[crtc]))
mod_timer(&dev->vblank_disable_timer, jiffies + 5*DRM_HZ);
@@ -460,8 +462,9 @@ void drm_vblank_pre_modeset(struct drm_device *dev,
int crtc)
* so that interrupts remain enabled in the interim.
*/
if (!dev->vblank_inmodeset[crtc]) {
- dev->vblank_inmodeset[crtc] = 1;
- drm_vblank_get(dev, crtc);
+ dev->vblank_inmodeset[crtc] = 0x1;
+ if (drm_vblank_get(dev, crtc) == 0)
+ dev->vblank_inmodeset[crtc] |= 0x2;
}
}
EXPORT_SYMBOL(drm_vblank_pre_modeset);
@@ -473,9 +476,12 @@ void drm_vblank_post_modeset(struct drm_device
*dev, int crtc)
if (dev->vblank_inmodeset[crtc]) {
spin_lock_irqsave(&dev->vbl_lock, irqflags);
dev->vblank_disable_allowed = 1;
- dev->vblank_inmodeset[crtc] = 0;
spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
- drm_vblank_put(dev, crtc);
+
+ if (dev->vblank_inmodeset[crtc] & 0x2)
+ drm_vblank_put(dev, crtc);
+
+ dev->vblank_inmodeset[crtc] = 0;
}
}
EXPORT_SYMBOL(drm_vblank_post_modeset);
--
1.6.0.4
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