[PATCH] drm/i915: Dump the contents of the GTT

[Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>]

Chasing wild speculation that we may be writing the wrong addresses
into the GTT for stolen objects, I would like to inspect those values.

Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Sedat Dilek <sedat.dilek@xxxxxxxxx>
---

Sedak, can you please apply this patch and then attach the contents of
/sys/kernel/debug/dri/0/i915_gem_gtt with the broken display?

---
 drivers/gpu/drm/i915/i915_debugfs.c | 47 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 10d864c..4edf65a 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -390,6 +390,51 @@ static int i915_gem_object_info(struct seq_file *m, void* data)
 	return 0;
 }
 
+static int i915_gem_gtt_contents(struct seq_file *m, struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	gen6_gtt_pte_t __iomem *gtt_entries;
+	gen6_gtt_pte_t scratch_pte;
+	gen6_gtt_pte_t zero[8] = {};
+	int i, j, last_zero = 0;
+	int ret;
+
+	if (INTEL_INFO(dev)->gen < 6)
+		return 0;
+
+	ret = mutex_lock_interruptible(&dev->struct_mutex);
+	if (ret)
+		return ret;
+
+	gtt_entries = (gen6_gtt_pte_t __iomem *)dev_priv->gtt.gsm;
+	scratch_pte = dev_priv->gtt.base.pte_encode(dev_priv->gtt.base.scratch.addr, I915_CACHE_LLC);
+	for (i = 0; i < gtt_total_entries(dev_priv->gtt); i += 8) {
+		gen6_gtt_pte_t pte[8];
+		int this_zero;
+
+		for (j = 0; j < 8; j++) {
+			pte[j] = ioread32(&gtt_entries[i+j]);
+			if (pte[j] == scratch_pte)
+				pte[j] = 0;
+		}
+
+		this_zero = memcmp(pte, zero, sizeof(pte)) == 0;
+		if (last_zero && this_zero) {
+			if (last_zero++ == 1)
+				seq_puts(m, "...\n");
+			continue;
+		}
+
+		seq_printf(m, "[%08x] %08x %08x %08x %08x %08x %08x %08x %08x\n",
+			   i, pte[0], pte[1], pte[2], pte[3], pte[4], pte[5], pte[6], pte[7]);
+		last_zero = this_zero;
+	}
+
+	mutex_unlock(&dev->struct_mutex);
+
+	return 0;
+}
+
 static int i915_gem_gtt_info(struct seq_file *m, void *data)
 {
 	struct drm_info_node *node = (struct drm_info_node *) m->private;
@@ -422,7 +467,7 @@ static int i915_gem_gtt_info(struct seq_file *m, void *data)
 	seq_printf(m, "Total %d objects, %zu bytes, %zu GTT size\n",
 		   count, total_obj_size, total_gtt_size);
 
-	return 0;
+	return i915_gem_gtt_contents(m, dev);
 }
 
 static int i915_gem_pageflip_info(struct seq_file *m, void *data)
-- 
1.8.4.rc2

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