nb/intel/sandybridge/raminit: Add Kconfig option for fuses

Add a new Kconfig option to ignore memory fuses that limit the
maximum DRAM frequency to be used. The option is disabled by
default and should only enabled by experienced users as it
might decrease system stability or prevent a successful RAM
training.

Remove conflicting devicetree settings.

Change-Id: I35dd78a02bcaafce8ba522d253c795d7835bacae
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/20907
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Nicola Corna <nicola@corna.info>

src/mainboard/lenovo/l520/devicetree.cb

@@ -15,9 +15,6 @@ chip northbridge/intel/sandybridge
 	register "gpu_panel_power_up_delay" = "0"
 	register "gpu_pch_backlight" = "0x00000000"
 
-	# Override fuse bits that hard-code the value to 666 Mhz
-	register "max_mem_clock_mhz" = "933"
-
 	device cpu_cluster 0x0 on
 		chip cpu/intel/socket_rPGA989
 			device lapic 0x0 on

src/mainboard/lenovo/t420/devicetree.cb

@@ -18,9 +18,6 @@ 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

@@ -17,9 +17,6 @@ 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/t430/devicetree.cb

@@ -34,9 +34,6 @@ chip northbridge/intel/sandybridge
 		end
 	end
 
-	# Override fuse bits that hard-code the value to 666 Mhz
-	register "max_mem_clock_mhz" = "933"
-
 	device domain 0x0 on
 		chip southbridge/intel/bd82x6x # Intel Series 6 Cougar Point PCH
 			register "c2_latency" = "0x0065"

src/mainboard/lenovo/t430s/devicetree.cb

@@ -17,9 +17,6 @@ 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

@@ -18,9 +18,6 @@ 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

@@ -18,9 +18,6 @@ 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/x1_carbon_gen1/devicetree.cb

@@ -15,9 +15,6 @@ chip northbridge/intel/sandybridge
 	register "gpu_panel_power_up_delay" = "300"
 	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

@@ -18,9 +18,6 @@ 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

@@ -18,9 +18,6 @@ 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/Kconfig

@@ -44,6 +44,18 @@ config USE_NATIVE_RAMINIT
 	  Select if you want to use coreboot implementation of raminit rather than
 	  System Agent/MRC.bin. You should answer Y.
 
+config NATIVE_RAMINIT_IGNORE_MAX_MEM_FUSES
+	bool "Ignore vendor programmed fuses that limit max. DRAM frequency"
+	default n
+	depends on USE_NATIVE_RAMINIT
+	help
+	  Ignore the mainboard's vendor programmed fuses that might limit the
+	  maximum DRAM frequency. By selecting this option the fuses will be
+	  ignored and the only limits on DRAM frequency are set by RAM's SPD and
+	  hard fuses in southbridge's clockgen.
+	  Disabled by default as it might causes system instability.
+	  Handle with care!
+
 config CBFS_SIZE
 	hex
 	default 0x100000

src/northbridge/intel/sandybridge/raminit_common.c

@@ -402,6 +402,9 @@ unsigned int get_mem_min_tck(void)
 
 	/* If this is zero, it just means devicetree.cb didn't set it */
 	if (!cfg || cfg->max_mem_clock_mhz == 0) {
+		if (IS_ENABLED(CONFIG_NATIVE_RAMINIT_IGNORE_MAX_MEM_FUSES))
+			return TCK_1333MHZ;
+
 		rev = pci_read_config8(PCI_DEV(0, 0, 0), PCI_DEVICE_ID);
 
 		if ((rev & BASE_REV_MASK) == BASE_REV_SNB) {