Quoting Rodrigo Vivi (2018-02-26 20:53:08)
> -void intel_fbc_handle_fifo_underrun_irq(struct drm_i915_private *dev_priv)
> -{
> - struct intel_fbc *fbc = &dev_priv->fbc;
> -
> - if (!fbc_supported(dev_priv))
> - return;
> -
> - /* There's no guarantee that underrun_detected won't be set to true
> - * right after this check and before the work is scheduled, but that's
> - * not a problem since we'll check it again under the work function
> - * while FBC is locked. This check here is just to prevent us from
> - * unnecessarily scheduling the work, and it relies on the fact that we
> - * never switch underrun_detect back to false after it's true. */
> - if (READ_ONCE(fbc->underrun_detected))
> - return;
> -
> - schedule_work(&fbc->underrun_work);
> -}
> +static void intel_handle_fifo_underrun_irq(struct drm_i915_private *dev_priv)
> +{
> + if (!HAS_FBC(dev_priv))
> + return;
> +
> + spin_lock(&dev_priv->underrun.lock);
> +
> + if (dev_priv->underrun.detected)
> + goto out;
> + dev_priv->underrun.detected = true;
> +
> + schedule_work(&dev_priv->underrun.work);
> +out:
> + spin_unlock(&dev_priv->underrun.lock);
This locking (or bool) isn't required by the following patch either. But
I presume the boolean is printed at some point, although that's probably
less useful than whatever FBC/SAGV would say about being disabled.
-Chris
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