From: Daniel Vetter Date: Thu, 8 Sep 2011 12:00:20 +0000 (+0200) Subject: drm/i915: close PM interrupt masking races in the irq handler X-Git-Tag: firefly_0821_release~3680^2~4279^2~2^2~39 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4fb066ab9ef3111c86d9fb8f13f1178885cf7f1c;p=firefly-linux-kernel-4.4.55.git drm/i915: close PM interrupt masking races in the irq handler Quoting Chris Wilson's more concise description: "Ah I think I see the problem. As you point out we only mask the current interrupt received, so that if we have a task pending (and so IMR != 0) we actually unmask the pending interrupt and so could receive it again before the tasklet is finally kicked off by the grumpy scheduler." We need the hw to issue PM interrupts A, B, A while the scheduler is hating us and refuses to run the rps work item. On receiving PM interrupt A we hit the WARN because dev_priv->pm_iir == PM_A | PM_B Also add a posting read as suggested by Chris to ensure proper ordering of the writes to PMIMR and PMIIR. Just in case somebody weakens write ordering. Signed-off-by: Daniel Vetter Reviewed-by: Ben Widawsky Reviewed-by: Chris Wilson Signed-off-by: Keith Packard --- diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index 944d712b752b..98eedddc7440 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -536,8 +536,9 @@ static irqreturn_t ivybridge_irq_handler(DRM_IRQ_ARGS) unsigned long flags; spin_lock_irqsave(&dev_priv->rps_lock, flags); WARN(dev_priv->pm_iir & pm_iir, "Missed a PM interrupt\n"); - I915_WRITE(GEN6_PMIMR, pm_iir); dev_priv->pm_iir |= pm_iir; + I915_WRITE(GEN6_PMIMR, dev_priv->pm_iir); + POSTING_READ(GEN6_PMIMR); spin_unlock_irqrestore(&dev_priv->rps_lock, flags); queue_work(dev_priv->wq, &dev_priv->rps_work); } @@ -649,8 +650,9 @@ static irqreturn_t ironlake_irq_handler(DRM_IRQ_ARGS) unsigned long flags; spin_lock_irqsave(&dev_priv->rps_lock, flags); WARN(dev_priv->pm_iir & pm_iir, "Missed a PM interrupt\n"); - I915_WRITE(GEN6_PMIMR, pm_iir); dev_priv->pm_iir |= pm_iir; + I915_WRITE(GEN6_PMIMR, dev_priv->pm_iir); + POSTING_READ(GEN6_PMIMR); spin_unlock_irqrestore(&dev_priv->rps_lock, flags); queue_work(dev_priv->wq, &dev_priv->rps_work); }