nb/intel/sandybridge/raminit: Allow 933Mhz on Lenovo devices

Set max_mem_clock_mhz in devicetree to 933Mhz.
Allows to run the memory at up to DDR3-1866.

The same frequency was allowed within the first vendor bios,
but Lenovo than decided to limit it to DDR3-1333.

Tested on Lenovo T520 and DDR3-1600 DIMM (RMT3170eb86e9w16).

The RAM is now running at DDR3-1600 instead of DDR3-1333.
This gives about 4% performance increase in glmark2 using the
Intel GPU.

Change-Id: If15be497402d84a2778f0434b6381a64eda832d6
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/15158
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Martin Roth <martinroth@google.com>

src/mainboard/lenovo/t420/devicetree.cb

@@ -18,6 +18,9 @@ chip northbridge/intel/sandybridge
 	register "gpu_cpu_backlight" = "0x1155"
 	register "gpu_pch_backlight" = "0x06100610"
 
+	# Override fuse bits that hard-code the value to 666 Mhz
+	register "max_mem_clock_mhz" = "933"
+
 	device cpu_cluster 0 on
 		chip cpu/intel/socket_rPGA988B
 			device lapic 0 on end

src/mainboard/lenovo/t420s/devicetree.cb

@@ -17,6 +17,9 @@ chip northbridge/intel/sandybridge
 	register "gpu_cpu_backlight" = "0x1155"
 	register "gpu_pch_backlight" = "0x06100610"
 
+	# Override fuse bits that hard-code the value to 666 Mhz
+	register "max_mem_clock_mhz" = "933"
+
 	device cpu_cluster 0 on
 		chip cpu/intel/socket_rPGA988B
 			device lapic 0 on end

src/mainboard/lenovo/t430s/devicetree.cb

@@ -17,6 +17,9 @@ chip northbridge/intel/sandybridge
 	register "gpu_cpu_backlight" = "0x1155"
 	register "gpu_pch_backlight" = "0x11551155"
 
+	# Override fuse bits that hard-code the value to 666 Mhz
+	register "max_mem_clock_mhz" = "933"
+
 	device cpu_cluster 0 on
 		chip cpu/intel/socket_rPGA989
 			device lapic 0 on end

src/mainboard/lenovo/t520/devicetree.cb

@@ -18,6 +18,9 @@ chip northbridge/intel/sandybridge
 	register "gpu_cpu_backlight" = "0x1155"
 	register "gpu_pch_backlight" = "0x06100610"
 
+	# Override fuse bits that hard-code the value to 666 Mhz
+	register "max_mem_clock_mhz" = "933"
+
 	device cpu_cluster 0 on
 		chip cpu/intel/socket_rPGA988B
 			device lapic 0 on end

src/mainboard/lenovo/t530/devicetree.cb

@@ -18,6 +18,9 @@ chip northbridge/intel/sandybridge
 	register "gpu_cpu_backlight" = "0x1155"
 	register "gpu_pch_backlight" = "0x11551155"
 
+	# Override fuse bits that hard-code the value to 666 Mhz
+	register "max_mem_clock_mhz" = "933"
+
 	device cpu_cluster 0 on
 		chip cpu/intel/socket_rPGA989
 			device lapic 0 on end

src/mainboard/lenovo/x220/devicetree.cb

@@ -18,6 +18,9 @@ chip northbridge/intel/sandybridge
 	register "gpu_cpu_backlight" = "0x1155"
 	register "gpu_pch_backlight" = "0x06100610"
 
+	# Override fuse bits that hard-code the value to 666 Mhz
+	register "max_mem_clock_mhz" = "933"
+
 	device cpu_cluster 0 on
 		chip cpu/intel/socket_rPGA989
 			device lapic 0 on end

src/mainboard/lenovo/x230/devicetree.cb

@@ -18,6 +18,9 @@ chip northbridge/intel/sandybridge
 	register "gpu_cpu_backlight" = "0x1155"
 	register "gpu_pch_backlight" = "0x11551155"
 
+	# Override fuse bits that hard-code the value to 666 Mhz
+	register "max_mem_clock_mhz" = "933"
+
 	device cpu_cluster 0 on
 		chip cpu/intel/socket_rPGA989
 			device lapic 0 on end

src/northbridge/intel/sandybridge/raminit.c

@@ -4374,7 +4374,11 @@ static unsigned int get_mem_min_tck(void)
 		}
 		return DEFAULT_TCK;
 	} else {
-		if (cfg->max_mem_clock_mhz >= 800)
+		if (cfg->max_mem_clock_mhz >= 1066)
+			return TCK_1066MHZ;
+		else if (cfg->max_mem_clock_mhz >= 933)
+			return TCK_933MHZ;
+		else if (cfg->max_mem_clock_mhz >= 800)
 			return TCK_800MHZ;
 		else if (cfg->max_mem_clock_mhz >= 666)
 			return TCK_666MHZ;