drm/i915/lmem: don't treat small BAR as an error

Just pass along the probed io_size. The backend should be able to
utilize the entire range here, even if some of it is non-mappable.

It does leave open with what to do with stolen local-memory.
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220315181425.576828-1-matthew.auld@intel.com

drivers/gpu/drm/i915/gt/intel_region_lmem.c

@@ -93,6 +93,7 @@ static struct intel_memory_region *setup_lmem(struct intel_gt *gt)
 	struct intel_memory_region *mem;
 	resource_size_t min_page_size;
 	resource_size_t io_start;
+	resource_size_t io_size;
 	resource_size_t lmem_size;
 	int err;
 
@@ -124,7 +125,8 @@ static struct intel_memory_region *setup_lmem(struct intel_gt *gt)
 
 
 	io_start = pci_resource_start(pdev, 2);
-	if (GEM_WARN_ON(lmem_size > pci_resource_len(pdev, 2)))
+	io_size = min(pci_resource_len(pdev, 2), lmem_size);
+	if (!io_size)
 		return ERR_PTR(-ENODEV);
 
 	min_page_size = HAS_64K_PAGES(i915) ? I915_GTT_PAGE_SIZE_64K :
@@ -134,7 +136,7 @@ static struct intel_memory_region *setup_lmem(struct intel_gt *gt)
 					 lmem_size,
 					 min_page_size,
 					 io_start,
-					 lmem_size,
+					 io_size,
 					 INTEL_MEMORY_LOCAL,
 					 0,
 					 &intel_region_lmem_ops);