[Intel-gfx] [PATCH] drm/i915: Fix errors when there is no free DSM

[José Roberto de Souza]

Part of DSM(data stolen memory) is reserved for HW functions and GUC
and in some platform this reserved block takes the whole DSM leaving
no memory to allocated by i915_gem_object_create_stolen() and friends.

In such cases i915_gem_init_stolen() was not calling drm_mm_init()
and returning 0, causing errors later when testing memory
(intel_memory_region_memtest()) and in intel_memory_regions_hw_probe()
saying setup of memory region failed:

checking generic (91000000 300000) vs hw (23fe7e000000 2000000)
checking generic (91000000 300000) vs hw (237800000000 800000000)
i915 0000:8c:00.0: [drm:i915_gem_init_stolen [i915]] GEN6_STOLEN_RESERVED = 0x00000003ff800185
i915 0000:8c:00.0: [drm:i915_gem_init_stolen [i915]] Memory reserved for graphics device: 8192K, usable: 0K
i915 0000:8c:00.0: Failed to read back from memory region:[mem 0x3ff800000-0x3ff7fffff] at [0x0000237bff800000 + 0x0000000000000000] for i915_gem_stolen_lmem_setup [i915]; wrote 0, read (ff, ff, ff)
i915 0000:8c:00.0: [drm] *ERROR* Failed to setup region 6 (type=3:0), error -22
[drm:intel_gt_setup_lmem [i915]] LMEM: debug trace data region: [0x0-0x2000000]
i915 0000:8c:00.0: [drm:intel_gt_setup_lmem [i915]] Local memory: [mem 0x00000000-0x3faffffff]

Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_stolen.c | 9 ++++++---
 drivers/gpu/drm/i915/intel_memory_region.c | 3 +++
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
index 26975d8577760..6e90357b2d1fd 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
@@ -495,13 +495,16 @@ static int i915_gem_init_stolen(struct intel_memory_region *mem)
 	 * memory, so just consider the start. */
 	reserved_total = stolen_top - reserved_base;
 
+	i915->stolen_usable_size =
+		resource_size(&i915->dsm) - reserved_total;
+
 	drm_dbg(&i915->drm,
 		"Memory reserved for graphics device: %lluK, usable: %lluK\n",
 		(u64)resource_size(&i915->dsm) >> 10,
-		((u64)resource_size(&i915->dsm) - reserved_total) >> 10);
+		(u64)i915->stolen_usable_size >> 10);
 
-	i915->stolen_usable_size =
-		resource_size(&i915->dsm) - reserved_total;
+	if (i915->stolen_usable_size == 0)
+		return -ENOMEM;
 
 	/* Basic memrange allocator for stolen space. */
 	drm_mm_init(&i915->mm.stolen, 0, i915->stolen_usable_size);
diff --git a/drivers/gpu/drm/i915/intel_memory_region.c b/drivers/gpu/drm/i915/intel_memory_region.c
index c70d7e286a512..317d67fa3a36e 100644
--- a/drivers/gpu/drm/i915/intel_memory_region.c
+++ b/drivers/gpu/drm/i915/intel_memory_region.c
@@ -324,6 +324,9 @@ int intel_memory_regions_hw_probe(struct drm_i915_private *i915)
 
 		if (IS_ERR(mem)) {
 			err = PTR_ERR(mem);
+			if (err == -ENOMEM)
+				continue;
+
 			drm_err(&i915->drm,
 				"Failed to setup region(%d) type=%d\n",
 				err, type);
-- 
2.34.1