drm/i915: ILK + VT-d workaround

Idle the GPU before doing any unmaps. We know if VT-d is in use through
an exported variable from iommu code.

This should avoid a known HW issue.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c
index 85151019dde1..80a7ed0a7df5 100644
--- a/drivers/char/agp/intel-gtt.c
+++ b/drivers/char/agp/intel-gtt.c
@@ -923,6 +923,9 @@ static int intel_fake_agp_insert_entries(struct agp_memory *mem,
 {
         int ret = -EINVAL;
 
+        if (intel_private.base.do_idle_maps)
+                return -ENODEV;
+
         if (intel_private.clear_fake_agp) {
                 int start = intel_private.base.stolen_size / PAGE_SIZE;
                 int end = intel_private.base.gtt_mappable_entries;
@@ -985,6 +988,9 @@ static int intel_fake_agp_remove_entries(struct agp_memory *mem,
         if (mem->page_count == 0)
                 return 0;
 
+        if (intel_private.base.do_idle_maps)
+                return -ENODEV;
+
         intel_gtt_clear_range(pg_start, mem->page_count);
 
         if (intel_private.base.needs_dmar) {
@@ -1177,6 +1183,25 @@ static void gen6_cleanup(void)
 {
 }
 
+/* Certain Gen5 chipsets require require idling the GPU before
+ * unmapping anything from the GTT when VT-d is enabled.
+ */
+extern int intel_iommu_gfx_mapped;
+static inline int needs_idle_maps(void)
+{
+        const unsigned short gpu_devid = intel_private.pcidev->device;
+
+        /* Query intel_iommu to see if we need the workaround. Presumably that
+         * was loaded first.
+         */
+        if ((gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_M_HB ||
+             gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_M_IG) &&
+             intel_iommu_gfx_mapped)
+                return 1;
+
+        return 0;
+}
+
 static int i9xx_setup(void)
 {
         u32 reg_addr;
@@ -1211,6 +1236,9 @@ static int i9xx_setup(void)
                 intel_private.gtt_bus_addr = reg_addr + gtt_offset;
         }
 
+        if (needs_idle_maps());
+                intel_private.base.do_idle_maps = 1;
+
         intel_i9xx_setup_flush();
 
         return 0;