[Intel-gfx] [PATCH] drm/i915: avoid processing spurious/shared interrupts in low-power states

[Chris Wilson]

On Fri, Feb 20, 2015 at 09:09:02PM +0200, Imre Deak wrote:
> +static void intel_irq_set_state(struct drm_i915_private *dev_priv,
> +				bool enabled)
> +{
> +	dev_priv->pm.irqs_enabled = enabled;
> +	/*
> +	 * Before we unmask the interrupt or synchronize against it, make sure
> +	 * that a corresponding interrupt handler running on another CPU sees
> +	 * the updated irqs_enabled value.
> +	 */
> +	smp_mb();

I would like a comment here to say something like: before powering down
the hardware make sure that we have no further access via pending
interrupt handlers. At the moment, I read the block comment above and
thought you were trying to imply something about the serialisation from
synchronize_irq() - but the only reason I can see you want sync_irq here
is to be sure that once the irq is disabled it is not going to run again.

> +	if (!enabled)
> +		synchronize_irq(dev_priv->dev->irq);
> +}

-- 
Chris Wilson, Intel Open Source Technology Centre