On Sat, 28 Feb 2015 18:02:33 +0300
Alexey Khoroshilov <khoroshilov@xxxxxxxxx> wrote:
> gma_power_begin() starts with locking power_ctrl_lock spinlock and then,
> if gma_resume_pci(dev->pdev) succeed, it calls
> psb_irq_preinstall(dev);
> psb_irq_postinstall(dev);
>
> psb_irq_postinstall() does some pipestat enabling/disabling dance:
> if (dev->vblank[0].enabled)
> psb_enable_pipestat(dev_priv, 0, PIPE_VBLANK_INTERRUPT_ENABLE);
> else
> psb_disable_pipestat(dev_priv, 0, PIPE_VBLANK_INTERRUPT_ENABLE);
>
> where
> void psb_enable_pipestat(struct drm_psb_private *dev_priv, int pipe, u32
> mask)
> {
> if ((dev_priv->pipestat[pipe] & mask) != mask) {
> u32 reg = psb_pipestat(pipe);
> dev_priv->pipestat[pipe] |= mask;
> /* Enable the interrupt, clear any pending status */
> if (gma_power_begin(dev_priv->dev, false)) {
> u32 writeVal = PSB_RVDC32(reg);
> writeVal |= (mask | (mask >> 16));
> PSB_WVDC32(writeVal, reg);
> (void) PSB_RVDC32(reg);
> gma_power_end(dev_priv->dev);
> }
> }
> }
>
> So, if a flag in dev_priv->pipestat[pipe] is not in agreement with
> dev->vblank[0].enabled,
> we will have a call to gma_power_begin() again and got an unavoidable
> deadlock.
I don't think it can ever happen in the current driver but the fix also
looks trivial. I think its sufficient to do this
commit 76d209fc77516f638c6db0342fddd0930d8e5957
Author: Alan <gnomes@xxxxxxxxxxxxxxxxxxx>
Date: Mon Mar 2 13:32:46 2015 +0000
gma500: drop the power lock before doing the irq pre/postinstall
The irq install is not locked or managed by the power lock. It will take the
lock again internally to do the vblank update so we would deadlock if a
change was ever needed.
diff --git a/drivers/gpu/drm/gma500/power.c b/drivers/gpu/drm/gma500/power.c
index b6b135f..8d101f4 100644
--- a/drivers/gpu/drm/gma500/power.c
+++ b/drivers/gpu/drm/gma500/power.c
@@ -266,11 +266,11 @@ bool gma_power_begin(struct drm_device *dev, bool force_on)
/* Ok power up needed */
ret = gma_resume_pci(dev->pdev);
if (ret == 0) {
- psb_irq_preinstall(dev);
- psb_irq_postinstall(dev);
pm_runtime_get(&dev->pdev->dev);
dev_priv->display_count++;
spin_unlock_irqrestore(&power_ctrl_lock, flags);
+ psb_irq_preinstall(dev);
+ psb_irq_postinstall(dev);
return true;
}
out_false:
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