[Intel-gfx] [PATCH v3 2/3] drm/i915: Fix hang on Ironlake mobile GPU with VT-d

[Dave Airlie]

> Under certain circumstances, an IOTLB flush never completes and the hardware
> just locks up.  The fix is meant to idle the GPU both before and after
> any unmap occurs, which should prevent the possibity to hang.

One comment below, noticed by building it for RHEL6.

>
> +/* Certain Gen5 chipsets require require idling the GPU before
> + * unmapping anything from the GTT when VT-d is enabled.
> + */
> +static inline int needs_idle_maps(void)
> +{
> +       u16 gmch_ctrl;
> +       const unsigned short gpu_devid = intel_private.pcidev->device;
> +       bool needs_dmar = USE_PCI_DMA_API;

^^ you don't use needs_dmar anywhere.

Dave.