From 4fb066ab9ef3111c86d9fb8f13f1178885cf7f1c Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Thu, 8 Sep 2011 14:00:20 +0200 Subject: [PATCH] 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 --- drivers/gpu/drm/i915/i915_irq.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index 944d712b752..98eedddc744 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); } -- 2.41.0