2 files changed, 47 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
index 62ef55ba061c..7465ab0fd396 100644
--- a/drivers/gpu/drm/i915/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
@@ -74,6 +74,50 @@ static unsigned long i915_stolen_to_physical(struct drm_device *dev)
         if (base == 0)
                 return 0;
 
+        /* make sure we don't clobber the GTT if it's within stolen memory */
+        if (INTEL_INFO(dev)->gen <= 4 && !IS_G33(dev) && !IS_G4X(dev)) {
+                struct {
+                        u32 start, end;
+                } stolen[2] = {
+                        { .start = base, .end = base + dev_priv->gtt.stolen_size, },
+                        { .start = base, .end = base + dev_priv->gtt.stolen_size, },
+                };
+                u64 gtt_start, gtt_end;
+
+                gtt_start = I915_READ(PGTBL_CTL);
+                if (IS_GEN4(dev))
+                        gtt_start = (gtt_start & PGTBL_ADDRESS_LO_MASK) |
+                                (gtt_start & PGTBL_ADDRESS_HI_MASK) << 28;
+                else
+                        gtt_start &= PGTBL_ADDRESS_LO_MASK;
+                gtt_end = gtt_start + gtt_total_entries(dev_priv->gtt) * 4;
+
+                if (gtt_start >= stolen[0].start && gtt_start < stolen[0].end)
+                        stolen[0].end = gtt_start;
+                if (gtt_end > stolen[1].start && gtt_end <= stolen[1].end)
+                        stolen[1].start = gtt_end;
+
+                /* pick the larger of the two chunks */
+                if (stolen[0].end - stolen[0].start >
+                    stolen[1].end - stolen[1].start) {
+                        base = stolen[0].start;
+                        dev_priv->gtt.stolen_size = stolen[0].end - stolen[0].start;
+                } else {
+                        base = stolen[1].start;
+                        dev_priv->gtt.stolen_size = stolen[1].end - stolen[1].start;
+                }
+
+                if (stolen[0].start != stolen[1].start ||
+                    stolen[0].end != stolen[1].end) {
+                        DRM_DEBUG_KMS("GTT within stolen memory at 0x%llx-0x%llx\n",
+                                      (unsigned long long) gtt_start,
+                                      (unsigned long long) gtt_end - 1);
+                        DRM_DEBUG_KMS("Stolen memory adjusted to 0x%x-0x%x\n",
+                                      base, base + (u32) dev_priv->gtt.stolen_size - 1);
+                }
+        }
+
+
         /* Verify that nothing else uses this physical address. Stolen
          * memory should be reserved by the BIOS and hidden from the
          * kernel. So if the region is already marked as busy, something
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index e691b30b2817..a5bab61bfc00 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -942,6 +942,9 @@ enum punit_power_well {
 /*
  * Instruction and interrupt control regs
  */
+#define PGTBL_CTL       0x02020
+#define   PGTBL_ADDRESS_LO_MASK 0xfffff000 /* bits [31:12] */
+#define   PGTBL_ADDRESS_HI_MASK 0x000000f0 /* bits [35:32] (gen4) */
 #define PGTBL_ER        0x02024
 #define RENDER_RING_BASE        0x02000
 #define BSD_RING_BASE           0x04000