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

On client platforms with reduced LMEM BAR, we should be able to continue
with driver load with reduced io_size. Instead of using the BAR size to
determine the how large stolen should be, we should instead use the
ADDR_RANGE register to figure this out(at least on platforms like DG2).
For simplicity we don't attempt to support partially mappable stolen.

v2: rearrange the io_mapping_init_wc slightly, since the stolen setup
might result in reduced io_size.
Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Co-developed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220315181425.576828-2-matthew.auld@intel.com

drivers/gpu/drm/i915/gem/i915_gem_stolen.c

@@ -12,6 +12,8 @@
 
 #include "gem/i915_gem_lmem.h"
 #include "gem/i915_gem_region.h"
+#include "gt/intel_gt.h"
+#include "gt/intel_region_lmem.h"
 #include "i915_drv.h"
 #include "i915_gem_stolen.h"
 #include "i915_reg.h"
@@ -492,7 +494,7 @@ static int i915_gem_init_stolen(struct intel_memory_region *mem)
 
 	/* Exclude the reserved region from driver use */
 	mem->region.end = reserved_base - 1;
-	mem->io_size = resource_size(&mem->region);
+	mem->io_size = min(mem->io_size, resource_size(&mem->region));
 
 	/* It is possible for the reserved area to end before the end of stolen
 	 * memory, so just consider the start. */
@@ -750,11 +752,6 @@ static int init_stolen_lmem(struct intel_memory_region *mem)
 	if (GEM_WARN_ON(resource_size(&mem->region) == 0))
 		return -ENODEV;
 
-	if (!io_mapping_init_wc(&mem->iomap,
-				mem->io_start,
-				mem->io_size))
-		return -EIO;
-
 	/*
 	 * TODO: For stolen lmem we mostly just care about populating the dsm
 	 * related bits and setting up the drm_mm allocator for the range.
@@ -762,18 +759,26 @@ static int init_stolen_lmem(struct intel_memory_region *mem)
 	 */
 	err = i915_gem_init_stolen(mem);
 	if (err)
-		goto err_fini;
+		return err;
+
+	if (mem->io_size && !io_mapping_init_wc(&mem->iomap,
+						mem->io_start,
+						mem->io_size)) {
+		err = -EIO;
+		goto err_cleanup;
+	}
 
 	return 0;
 
-err_fini:
-	io_mapping_fini(&mem->iomap);
+err_cleanup:
+	i915_gem_cleanup_stolen(mem->i915);
 	return err;
 }
 
 static int release_stolen_lmem(struct intel_memory_region *mem)
 {
-	io_mapping_fini(&mem->iomap);
+	if (mem->io_size)
+		io_mapping_fini(&mem->iomap);
 	i915_gem_cleanup_stolen(mem->i915);
 	return 0;
 }
@@ -790,25 +795,43 @@ i915_gem_stolen_lmem_setup(struct drm_i915_private *i915, u16 type,
 {
 	struct intel_uncore *uncore = &i915->uncore;
 	struct pci_dev *pdev = to_pci_dev(i915->drm.dev);
+	resource_size_t dsm_size, dsm_base, lmem_size;
 	struct intel_memory_region *mem;
+	resource_size_t io_start, io_size;
 	resource_size_t min_page_size;
-	resource_size_t io_start;
-	resource_size_t lmem_size;
-	u64 lmem_base;
 
-	lmem_base = intel_uncore_read64(uncore, GEN12_DSMBASE);
-	if (GEM_WARN_ON(lmem_base >= pci_resource_len(pdev, 2)))
+	if (WARN_ON_ONCE(instance))
 		return ERR_PTR(-ENODEV);
 
-	lmem_size = pci_resource_len(pdev, 2) - lmem_base;
-	io_start = pci_resource_start(pdev, 2) + lmem_base;
+	/* Use DSM base address instead for stolen memory */
+	dsm_base = intel_uncore_read64(uncore, GEN12_DSMBASE);
+	if (IS_DG1(uncore->i915)) {
+		lmem_size = pci_resource_len(pdev, 2);
+		if (WARN_ON(lmem_size < dsm_base))
+			return ERR_PTR(-ENODEV);
+	} else {
+		resource_size_t lmem_range;
+
+		lmem_range = intel_gt_read_register(&i915->gt0, XEHPSDV_TILE0_ADDR_RANGE) & 0xFFFF;
+		lmem_size = lmem_range >> XEHPSDV_TILE_LMEM_RANGE_SHIFT;
+		lmem_size *= SZ_1G;
+	}
+
+	dsm_size = lmem_size - dsm_base;
+	if (pci_resource_len(pdev, 2) < lmem_size) {
+		io_start = 0;
+		io_size = 0;
+	} else {
+		io_start = pci_resource_start(pdev, 2) + dsm_base;
+		io_size = dsm_size;
+	}
 
 	min_page_size = HAS_64K_PAGES(i915) ? I915_GTT_PAGE_SIZE_64K :
 						I915_GTT_PAGE_SIZE_4K;
 
-	mem = intel_memory_region_create(i915, lmem_base, lmem_size,
+	mem = intel_memory_region_create(i915, dsm_base, dsm_size,
 					 min_page_size,
-					 io_start, lmem_size,
+					 io_start, io_size,
 					 type, instance,
 					 &i915_region_stolen_lmem_ops);
 	if (IS_ERR(mem))
@@ -822,6 +845,7 @@ i915_gem_stolen_lmem_setup(struct drm_i915_private *i915, u16 type,
 
 	drm_dbg(&i915->drm, "Stolen Local memory IO start: %pa\n",
 		&mem->io_start);
+	drm_dbg(&i915->drm, "Stolen Local DSM base: %pa\n", &dsm_base);
 
 	intel_memory_region_set_name(mem, "stolen-local");
 

drivers/gpu/drm/i915/i915_reg.h

@@ -8464,6 +8464,9 @@ enum skl_power_gate {
 #define   SGGI_DIS			REG_BIT(15)
 #define   SGR_DIS			REG_BIT(13)
 
+#define XEHPSDV_TILE0_ADDR_RANGE	_MMIO(0x4900)
+#define   XEHPSDV_TILE_LMEM_RANGE_SHIFT  8
+
 #define XEHPSDV_FLAT_CCS_BASE_ADDR	_MMIO(0x4910)
 #define   XEHPSDV_CCS_BASE_SHIFT	8