drm/i915: Fix DRAM size reporting for BXT

The BXT DUNIT register tells us the size of each DRAM device
in Gb. We want to report the size of the whole DIMM in GB, so
that it matches how we report it for non-LP platforms.

v2: Deobfuscate the math (Chris)
    s/GB/GBIT/ in the register bit definitions (Jani)
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190306203551.24592-6-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/i915_drv.c

@@ -1242,15 +1242,15 @@ skl_get_dram_info(struct drm_i915_private *dev_priv)
 static int bxt_get_dimm_size(u32 val)
 {
 	switch (val & BXT_DRAM_SIZE_MASK) {
-	case BXT_DRAM_SIZE_4GB:
+	case BXT_DRAM_SIZE_4GBIT:
 		return 4;
-	case BXT_DRAM_SIZE_6GB:
+	case BXT_DRAM_SIZE_6GBIT:
 		return 6;
-	case BXT_DRAM_SIZE_8GB:
+	case BXT_DRAM_SIZE_8GBIT:
 		return 8;
-	case BXT_DRAM_SIZE_12GB:
+	case BXT_DRAM_SIZE_12GBIT:
 		return 12;
-	case BXT_DRAM_SIZE_16GB:
+	case BXT_DRAM_SIZE_16GBIT:
 		return 16;
 	default:
 		MISSING_CASE(val);
@@ -1287,9 +1287,14 @@ static int bxt_get_dimm_ranks(u32 val)
 static void bxt_get_dimm_info(struct dram_dimm_info *dimm,
 			      u32 val)
 {
-	dimm->size = bxt_get_dimm_size(val);
 	dimm->width = bxt_get_dimm_width(val);
 	dimm->ranks = bxt_get_dimm_ranks(val);
+
+	/*
+	 * Size in register is Gb per DRAM device. Convert to total
+	 * GB to match the way we report this for non-LP platforms.
+	 */
+	dimm->size = bxt_get_dimm_size(val) * intel_dimm_num_devices(dimm) / 8;
 }
 
 static int

drivers/gpu/drm/i915/i915_reg.h

@@ -9856,11 +9856,11 @@ enum skl_power_gate {
 #define  BXT_DRAM_WIDTH_X64			(0x3 << 4)
 #define  BXT_DRAM_SIZE_MASK			(0x7 << 6)
 #define  BXT_DRAM_SIZE_SHIFT			6
-#define  BXT_DRAM_SIZE_4GB			(0x0 << 6)
-#define  BXT_DRAM_SIZE_6GB			(0x1 << 6)
-#define  BXT_DRAM_SIZE_8GB			(0x2 << 6)
-#define  BXT_DRAM_SIZE_12GB			(0x3 << 6)
-#define  BXT_DRAM_SIZE_16GB			(0x4 << 6)
+#define  BXT_DRAM_SIZE_4GBIT			(0x0 << 6)
+#define  BXT_DRAM_SIZE_6GBIT			(0x1 << 6)
+#define  BXT_DRAM_SIZE_8GBIT			(0x2 << 6)
+#define  BXT_DRAM_SIZE_12GBIT			(0x3 << 6)
+#define  BXT_DRAM_SIZE_16GBIT			(0x4 << 6)
 
 #define SKL_MEMORY_FREQ_MULTIPLIER_HZ		266666666
 #define SKL_MC_BIOS_DATA_0_0_0_MCHBAR_PCU	_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x5E04)