drm/i915: use the ICL stolen memory

Now that our stolen memory is already reserved by the x86 subsystem
(since commit "x86/gpu: reserve ICL's graphics stolen memory"), make
use of it.

Cc: Joonas Lahtinen <[e-mail]>
Cc: Daniele Ceraolo Spurio <[e-mail]>
Cc: [e-mail]
Signed-off-by: Paulo Zanoni <[e-mail]>
Reviewed-by: Rodrigo Vivi <[e-mail]>
Signed-off-by: Rodrigo Vivi <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/i915_gem_stolen.c

···
 	*size = stolen_top - *base;
 }
 
+static void icl_get_stolen_reserved(struct drm_i915_private *dev_priv,
+				    resource_size_t *base,
+				    resource_size_t *size)
+{
+	u64 reg_val = I915_READ64(GEN6_STOLEN_RESERVED);
+
+	DRM_DEBUG_DRIVER("GEN6_STOLEN_RESERVED = 0x%016llx\n", reg_val);
+
+	*base = reg_val & GEN11_STOLEN_RESERVED_ADDR_MASK;
+
+	switch (reg_val & GEN8_STOLEN_RESERVED_SIZE_MASK) {
+	case GEN8_STOLEN_RESERVED_1M:
+		*size = 1024 * 1024;
+		break;
+	case GEN8_STOLEN_RESERVED_2M:
+		*size = 2 * 1024 * 1024;
+		break;
+	case GEN8_STOLEN_RESERVED_4M:
+		*size = 4 * 1024 * 1024;
+		break;
+	case GEN8_STOLEN_RESERVED_8M:
+		*size = 8 * 1024 * 1024;
+		break;
+	default:
+		*size = 8 * 1024 * 1024;
+		MISSING_CASE(reg_val & GEN8_STOLEN_RESERVED_SIZE_MASK);
+	}
+}
+
 int i915_gem_init_stolen(struct drm_i915_private *dev_priv)
 {
 	resource_size_t reserved_base, stolen_top;
···
 			gen7_get_stolen_reserved(dev_priv,
 						 &reserved_base, &reserved_size);
 		break;
-	default:
+	case 8:
+	case 9:
+	case 10:
 		if (IS_LP(dev_priv))
 			chv_get_stolen_reserved(dev_priv,
 						&reserved_base, &reserved_size);
 		else
 			bdw_get_stolen_reserved(dev_priv,
 						&reserved_base, &reserved_size);
+		break;
+	case 11:
+	default:
+		icl_get_stolen_reserved(dev_priv, &reserved_base,
+					&reserved_size);
 		break;
 	}
 

drivers/gpu/drm/i915/i915_reg.h

···
 #define GEN8_STOLEN_RESERVED_4M		(2 << 7)
 #define GEN8_STOLEN_RESERVED_8M		(3 << 7)
 #define GEN6_STOLEN_RESERVED_ENABLE	(1 << 0)
+#define GEN11_STOLEN_RESERVED_ADDR_MASK	(0xFFFFFFFFFFFULL << 20)
 
 /* VGA stuff */