[Intel-gfx] [PATCH] drm/i915: Check stolen memory size before calling drm_mm_init

[José Roberto de Souza]

Add check for zero usable stolen memory before calling drm_mm_init
to support configurations where stolen memory exists but is fully
reserved.

Also skip memory test in such case.

Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
Cc: Lucas De Marchi <lucas.demarchi at intel.com>
Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
Signed-off-by: Steve Carbonari <steven.carbonari at intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_stolen.c | 9 ++++++---
 drivers/gpu/drm/i915/intel_memory_region.c | 8 ++++++--
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
index b9c3196b91cab..636cdf8a73b0a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
@@ -497,13 +497,16 @@ 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 0;
 
 	/* 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..1cbe194e01f6b 100644
--- a/drivers/gpu/drm/i915/intel_memory_region.c
+++ b/drivers/gpu/drm/i915/intel_memory_region.c
@@ -97,10 +97,14 @@ static int iomemtest(struct intel_memory_region *mem,
 		     bool test_all,
 		     const void *caller)
 {
-	resource_size_t last = resource_size(&mem->region) - PAGE_SIZE;
-	resource_size_t page;
+	resource_size_t last, page;
 	int err;
 
+	if (resource_size(&mem->region) == 0)
+		return 0;
+
+	last = resource_size(&mem->region) - PAGE_SIZE;
+
 	/*
 	 * Quick test to check read/write access to the iomap (backing store).
 	 *
-- 
2.35.1