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>

2 files changed, 58 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;
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 7a709cd8d543..6042c5e6d278 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -49,6 +49,28 @@ static unsigned int cache_level_to_agp_type(struct drm_device *dev,
         }
 }
 
+static bool do_idling(struct drm_i915_private *dev_priv)
+{
+        bool ret = dev_priv->mm.interruptible;
+
+        if (unlikely(dev_priv->mm.gtt->do_idle_maps)) {
+                dev_priv->mm.interruptible = false;
+                if (i915_gpu_idle(dev_priv->dev)) {
+                        DRM_ERROR("Couldn't idle GPU\n");
+                        /* Wait a bit, in hopes it avoids the hang */
+                        udelay(10);
+                }
+        }
+
+        return ret;
+}
+
+static void undo_idling(struct drm_i915_private *dev_priv, bool interruptible)
+{
+        if (unlikely(dev_priv->mm.gtt->do_idle_maps))
+                dev_priv->mm.interruptible = interruptible;
+}
+
 void i915_gem_restore_gtt_mappings(struct drm_device *dev)
 {
         struct drm_i915_private *dev_priv = dev->dev_private;
@@ -117,6 +139,12 @@ void i915_gem_gtt_rebind_object(struct drm_i915_gem_object *obj,
 
 void i915_gem_gtt_unbind_object(struct drm_i915_gem_object *obj)
 {
+        struct drm_device *dev = obj->base.dev;
+        struct drm_i915_private *dev_priv = dev->dev_private;
+        bool interruptible;
+
+        interruptible = do_idling(dev_priv);
+
         intel_gtt_clear_range(obj->gtt_space->start >> PAGE_SHIFT,
                               obj->base.size >> PAGE_SHIFT);
 
@@ -124,4 +152,6 @@ void i915_gem_gtt_unbind_object(struct drm_i915_gem_object *obj)
                 intel_gtt_unmap_memory(obj->sg_list, obj->num_sg);
                 obj->sg_list = NULL;
         }
+
+        undo_idling(dev_priv, interruptible);
 }