drm/i915/lmem: Enable lmem for platforms with Flat CCS

A portion of device memory is reserved for Flat CCS so usable
device memory will be reduced by size of Flat CCS. Size of
Flat CCS is specified in “XEHPSDV_FLAT_CCS_BASE_ADDR”.
So to get effective device memory we need to subtract
total device memory by Flat CCS memory size.

v2:
  Addressed the small bar related issue [Matt]
  Removed a reduntant check [Matt]
v3:
  removed a variable
  s/DRM_ERROR/drm_err [Lucas]

Cc: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220218184752.7524-15-ramalingam.c@intel.com

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

@@ -908,6 +908,25 @@ u32 intel_gt_read_register_fw(struct intel_gt *gt, i915_reg_t reg)
 	return intel_uncore_read_fw(gt->uncore, reg);
 }
 
+u32 intel_gt_read_register(struct intel_gt *gt, i915_reg_t reg)
+{
+	int type;
+	u8 sliceid, subsliceid;
+
+	for (type = 0; type < NUM_STEERING_TYPES; type++) {
+		if (intel_gt_reg_needs_read_steering(gt, reg, type)) {
+			intel_gt_get_valid_steering(gt, type, &sliceid,
+						    &subsliceid);
+			return intel_uncore_read_with_mcr_steering(gt->uncore,
+								   reg,
+								   sliceid,
+								   subsliceid);
+		}
+	}
+
+	return intel_uncore_read(gt->uncore, reg);
+}
+
 void intel_gt_info_print(const struct intel_gt_info *info,
 			 struct drm_printer *p)
 {

drivers/gpu/drm/i915/gt/intel_gt.h

@@ -85,6 +85,7 @@ static inline bool intel_gt_needs_read_steering(struct intel_gt *gt,
 }
 
 u32 intel_gt_read_register_fw(struct intel_gt *gt, i915_reg_t reg);
+u32 intel_gt_read_register(struct intel_gt *gt, i915_reg_t reg);
 
 void intel_gt_info_print(const struct intel_gt_info *info,
 			 struct drm_printer *p);

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

@@ -97,8 +97,29 @@ static struct intel_memory_region *setup_lmem(struct intel_gt *gt)
 	if (!IS_DGFX(i915))
 		return ERR_PTR(-ENODEV);
 
-	/* Stolen starts from GSMBASE on DG1 */
-	lmem_size = intel_uncore_read64(uncore, GEN12_GSMBASE);
+	if (HAS_FLAT_CCS(i915)) {
+		u64 tile_stolen, flat_ccs_base;
+
+		lmem_size = pci_resource_len(pdev, 2);
+		flat_ccs_base = intel_gt_read_register(gt, XEHPSDV_FLAT_CCS_BASE_ADDR);
+		flat_ccs_base = (flat_ccs_base >> XEHPSDV_CCS_BASE_SHIFT) * SZ_64K;
+
+		if (GEM_WARN_ON(lmem_size < flat_ccs_base))
+			return ERR_PTR(-ENODEV);
+
+		tile_stolen = lmem_size - flat_ccs_base;
+
+		/* If the FLAT_CCS_BASE_ADDR register is not populated, flag an error */
+		if (tile_stolen == lmem_size)
+			drm_err(&i915->drm,
+				"CCS_BASE_ADDR register did not have expected value\n");
+
+		lmem_size -= tile_stolen;
+	} else {
+		/* Stolen starts from GSMBASE without CCS */
+		lmem_size = intel_uncore_read64(&i915->uncore, GEN12_GSMBASE);
+	}
+
 
 	io_start = pci_resource_start(pdev, 2);
 	if (GEM_WARN_ON(lmem_size > pci_resource_len(pdev, 2)))

drivers/gpu/drm/i915/i915_reg.h

@@ -12645,6 +12645,9 @@ enum skl_power_gate {
 #define   SGGI_DIS			REG_BIT(15)
 #define   SGR_DIS			REG_BIT(13)
 
+#define XEHPSDV_FLAT_CCS_BASE_ADDR	_MMIO(0x4910)
+#define   XEHPSDV_CCS_BASE_SHIFT	8
+
 /* gamt regs */
 #define GEN8_L3_LRA_1_GPGPU _MMIO(0x4dd4)
 #define   GEN8_L3_LRA_1_GPGPU_DEFAULT_VALUE_BDW  0x67F1427F /* max/min for LRA1/2 */