soc/intel/xeon_sp: Add read CPU PPIN MSR function

These changes are in accordance with the documentation:
[*] page 208-209
    Intel(R) 64 and IA-32 Architectures, Software Developer’s Manual,
    Volume 4: Model-Specific Registers. May 2019.
    Order Number: 335592-070US

Tested on OCP Tioga Pass and Delta Lake.

Change-Id: I8c2eac055a065c06859a3cb7b48ed59f15ae2fc4
Signed-off-by: Johnny Lin <johnny_lin@wiwynn.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42901
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-by: Jonathan Zhang <jonzhang@fb.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/xeon_sp/cpx/cpu.c

@@ -188,3 +188,34 @@ void cpx_init_cpus(struct device *dev)
 	/* update numa domain for all cpu devices */
 	xeonsp_init_cpu_config();
 }
+
+msr_t read_msr_ppin(void)
+{
+	msr_t ppin = {0};
+	msr_t msr;
+
+	/* If MSR_PLATFORM_INFO PPIN_CAP is 0, PPIN capability is not supported */
+	msr = rdmsr(MSR_PLATFORM_INFO);
+	if ((msr.lo & MSR_PPIN_CAP) == 0) {
+		printk(BIOS_ERR, "MSR_PPIN_CAP is 0, PPIN is not supported\n");
+		return ppin;
+	}
+
+	/* Access to MSR_PPIN is permitted only if MSR_PPIN_CTL LOCK is 0 and ENABLE is 1 */
+	msr = rdmsr(MSR_PPIN_CTL);
+	if (msr.lo & MSR_PPIN_CTL_LOCK) {
+		printk(BIOS_ERR, "MSR_PPIN_CTL_LOCK is 1, PPIN access is not allowed\n");
+		return ppin;
+	}
+
+	if ((msr.lo & MSR_PPIN_CTL_ENABLE) == 0) {
+		/* Set MSR_PPIN_CTL ENABLE to 1 */
+		msr.lo |= MSR_PPIN_CTL_ENABLE;
+		wrmsr(MSR_PPIN_CTL, msr);
+	}
+	ppin = rdmsr(MSR_PPIN);
+	/* Set enable to 0 after reading MSR_PPIN */
+	msr.lo &= ~MSR_PPIN_CTL_ENABLE;
+	wrmsr(MSR_PPIN_CTL, msr);
+	return ppin;
+}

src/soc/intel/xeon_sp/cpx/include/soc/cpu.h

@@ -4,6 +4,7 @@
 #define _SOC_CPU_H
 
 #include <device/device.h>
+#include <cpu/x86/msr.h>
 
 #define CPUID_COOPERLAKE_SP_A0			0x05065a
 
@@ -11,5 +12,6 @@
 #define CPU_BCLK 100
 
 void cpx_init_cpus(struct device *dev);
+msr_t read_msr_ppin(void);
 
 #endif

src/soc/intel/xeon_sp/skx/cpu.c

@@ -244,3 +244,34 @@ void xeon_sp_init_cpus(struct device *dev)
 
 	FUNC_EXIT();
 }
+
+msr_t read_msr_ppin(void)
+{
+	msr_t ppin = {0};
+	msr_t msr;
+
+	/* If MSR_PLATFORM_INFO PPIN_CAP is 0, PPIN capability is not supported */
+	msr = rdmsr(MSR_PLATFORM_INFO);
+	if ((msr.lo & MSR_PPIN_CAP) == 0) {
+		printk(BIOS_ERR, "MSR_PPIN_CAP is 0, PPIN is not supported\n");
+		return ppin;
+	}
+
+	/* Access to MSR_PPIN is permitted only if MSR_PPIN_CTL LOCK is 0 and ENABLE is 1 */
+	msr = rdmsr(MSR_PPIN_CTL);
+	if (msr.lo & MSR_PPIN_CTL_LOCK) {
+		printk(BIOS_ERR, "MSR_PPIN_CTL_LOCK is 1, PPIN access is not allowed\n");
+		return ppin;
+	}
+
+	if ((msr.lo & MSR_PPIN_CTL_ENABLE) == 0) {
+		/* Set MSR_PPIN_CTL ENABLE to 1 */
+		msr.lo |= MSR_PPIN_CTL_ENABLE;
+		wrmsr(MSR_PPIN_CTL, msr);
+	}
+	ppin = rdmsr(MSR_PPIN);
+	/* Set enable to 0 after reading MSR_PPIN */
+	msr.lo &= ~MSR_PPIN_CTL_ENABLE;
+	wrmsr(MSR_PPIN_CTL, msr);
+	return ppin;
+}

src/soc/intel/xeon_sp/skx/include/soc/cpu.h

@@ -4,6 +4,7 @@
 #define _SOC_CPU_H_
 
 #include <device/device.h>
+#include <cpu/x86/msr.h>
 
 /* SKXSP CPUID */
 #define CPUID_SKYLAKE_SP_A0_A1 0x506f0
@@ -15,5 +16,6 @@
 
 int get_cpu_count(void);
 void xeon_sp_init_cpus(struct device *dev);
+msr_t read_msr_ppin(void);
 
 #endif