cpu/intel/model_206ax: Lock MSR_PP_CURRENT_CONFIG

Now that those registers are only written once set the lock bit to
protect it from runtime changes.

TEST: Lenovo X220 still boots.

Change-Id: I4c56a3cb322a0e75eb3dd366808068093928e10c
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78608
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/cpu/intel/model_206ax/model_206ax.h

@@ -73,8 +73,10 @@
 #define  PKG_POWER_LIMIT_TIME_MASK	0x7f
 
 #define MSR_PP0_CURRENT_CONFIG		0x601
+#define  PP0_CURRENT_LIMIT_LOCK		(1U << 31)
 #define  PP0_CURRENT_LIMIT		(112 << 3) /* 112 A */
 #define MSR_PP1_CURRENT_CONFIG		0x602
+#define  PP1_CURRENT_LIMIT_LOCK		(1U << 31)
 #define  PP1_CURRENT_LIMIT_SNB		(35 << 3) /* 35 A */
 #define  PP1_CURRENT_LIMIT_IVB		(50 << 3) /* 50 A */
 #define MSR_PKG_POWER_SKU_UNIT		0x606

src/cpu/intel/model_206ax/model_206ax_init.c

@@ -206,6 +206,7 @@ static void configure_c_states(void)
 		msr = rdmsr(MSR_PP0_CURRENT_CONFIG);
 		msr.lo &= ~0x1fff;
 		msr.lo |= PP0_CURRENT_LIMIT;
+		msr.lo |= PP0_CURRENT_LIMIT_LOCK;
 		wrmsr(MSR_PP0_CURRENT_CONFIG, msr);
 
 		/* Secondary Plane Current Limit */
@@ -215,6 +216,7 @@ static void configure_c_states(void)
 			msr.lo |= PP1_CURRENT_LIMIT_IVB;
 		else
 			msr.lo |= PP1_CURRENT_LIMIT_SNB;
+		msr.lo |= PP1_CURRENT_LIMIT_LOCK;
 		wrmsr(MSR_PP1_CURRENT_CONFIG, msr);
 	}
 }