[Intel-gfx] [PATCH 1/4] intel-iommu: Workaround IOTLB hang on Ironlake GPU

[Ben Widawsky]

From: David Woodhouse <dwmw2 at infradead.org>

To work around a hardware issue, we have to submit IOTLB flushes while
the graphics engine is idle. The graphics driver will (we hope) go to
great lengths to ensure that it gets that right on the affected
chipset(s)... so let's not screw it over by deferring the unmap and
doing it later. That wouldn't be very helpful.

Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/iommu/intel-iommu.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index c621c98..ff26603 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3950,7 +3950,11 @@ static void __devinit quirk_calpella_no_shadow_gtt(struct pci_dev *dev)
 	if (!(ggc & GGC_MEMORY_VT_ENABLED)) {
 		printk(KERN_INFO "DMAR: BIOS has allocated no shadow GTT; disabling IOMMU for graphics\n");
 		dmar_map_gfx = 0;
-	}
+	} else if (dmar_map_gfx) {
+		/* we have to ensure the gfx device is idle before we flush */
+		printk(KERN_INFO "DMAR: Disabling batched IOTLB flush on Ironlake\n");
+		intel_iommu_strict = 1;
+       }
 }
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x0040, quirk_calpella_no_shadow_gtt);
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x0044, quirk_calpella_no_shadow_gtt);
-- 
1.7.7