[Intel-gfx] [PATCH 3/4] drm/i915: Move underrun work from fbc to fifo_underrun.

[Chris Wilson]

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