drm/i915: move gen6 rps handling to workqueue
The render P-state handling code requires reading from a GT register.
This means that FORCEWAKE must be written to, a resource which is shared
and should be protected by struct_mutex. Hence we can not manipulate
that register from within the interrupt handling and so must delegate
the task to a workqueue.
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Keith Packard <keithp@keithp.com>
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index edd208e..5be2aa0 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -367,22 +367,30 @@
jiffies + msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
}
-static void gen6_pm_irq_handler(struct drm_device *dev)
+static void gen6_pm_rps_work(struct work_struct *work)
{
- drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
+ drm_i915_private_t *dev_priv = container_of(work, drm_i915_private_t,
+ rps_work);
u8 new_delay = dev_priv->cur_delay;
- u32 pm_iir;
+ u32 pm_iir, pm_imr;
- pm_iir = I915_READ(GEN6_PMIIR);
+ spin_lock_irq(&dev_priv->rps_lock);
+ pm_iir = dev_priv->pm_iir;
+ dev_priv->pm_iir = 0;
+ pm_imr = I915_READ(GEN6_PMIMR);
+ spin_unlock_irq(&dev_priv->rps_lock);
+
if (!pm_iir)
return;
+ mutex_lock(&dev_priv->dev->struct_mutex);
if (pm_iir & GEN6_PM_RP_UP_THRESHOLD) {
if (dev_priv->cur_delay != dev_priv->max_delay)
new_delay = dev_priv->cur_delay + 1;
if (new_delay > dev_priv->max_delay)
new_delay = dev_priv->max_delay;
} else if (pm_iir & (GEN6_PM_RP_DOWN_THRESHOLD | GEN6_PM_RP_DOWN_TIMEOUT)) {
+ gen6_gt_force_wake_get(dev_priv);
if (dev_priv->cur_delay != dev_priv->min_delay)
new_delay = dev_priv->cur_delay - 1;
if (new_delay < dev_priv->min_delay) {
@@ -396,12 +404,19 @@
I915_WRITE(GEN6_RP_INTERRUPT_LIMITS,
I915_READ(GEN6_RP_INTERRUPT_LIMITS) & ~0x3f0000);
}
+ gen6_gt_force_wake_put(dev_priv);
}
- gen6_set_rps(dev, new_delay);
+ gen6_set_rps(dev_priv->dev, new_delay);
dev_priv->cur_delay = new_delay;
- I915_WRITE(GEN6_PMIIR, pm_iir);
+ /*
+ * rps_lock not held here because clearing is non-destructive. There is
+ * an *extremely* unlikely race with gen6_rps_enable() that is prevented
+ * by holding struct_mutex for the duration of the write.
+ */
+ I915_WRITE(GEN6_PMIMR, pm_imr & ~pm_iir);
+ mutex_unlock(&dev_priv->dev->struct_mutex);
}
static void pch_irq_handler(struct drm_device *dev)
@@ -525,13 +540,30 @@
i915_handle_rps_change(dev);
}
- if (IS_GEN6(dev))
- gen6_pm_irq_handler(dev);
+ if (IS_GEN6(dev) && pm_iir & GEN6_PM_DEFERRED_EVENTS) {
+ /*
+ * IIR bits should never already be set because IMR should
+ * prevent an interrupt from being shown in IIR. The warning
+ * displays a case where we've unsafely cleared
+ * dev_priv->pm_iir. Although missing an interrupt of the same
+ * type is not a problem, it displays a problem in the logic.
+ *
+ * The mask bit in IMR is cleared by rps_work.
+ */
+ 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;
+ spin_unlock_irqrestore(&dev_priv->rps_lock, flags);
+ queue_work(dev_priv->wq, &dev_priv->rps_work);
+ }
/* should clear PCH hotplug event before clear CPU irq */
I915_WRITE(SDEIIR, pch_iir);
I915_WRITE(GTIIR, gt_iir);
I915_WRITE(DEIIR, de_iir);
+ I915_WRITE(GEN6_PMIIR, pm_iir);
done:
I915_WRITE(DEIER, de_ier);
@@ -1658,6 +1690,7 @@
INIT_WORK(&dev_priv->hotplug_work, i915_hotplug_work_func);
INIT_WORK(&dev_priv->error_work, i915_error_work_func);
+ INIT_WORK(&dev_priv->rps_work, gen6_pm_rps_work);
if (HAS_PCH_SPLIT(dev)) {
ironlake_irq_preinstall(dev);