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-rw-r--r--src/soc/intel/apollolake/bootblock/bootblock.c9
-rw-r--r--src/soc/intel/apollolake/include/soc/cpu.h3
2 files changed, 10 insertions, 2 deletions
diff --git a/src/soc/intel/apollolake/bootblock/bootblock.c b/src/soc/intel/apollolake/bootblock/bootblock.c
index cd23f5984b..77d98d98be 100644
--- a/src/soc/intel/apollolake/bootblock/bootblock.c
+++ b/src/soc/intel/apollolake/bootblock/bootblock.c
@@ -41,8 +41,13 @@ static void enable_pm_timer(void)
{
/* ACPI PM timer emulation */
msr_t msr;
- /* Multiplier value that somehow 3.579545MHz freq */
- msr.hi = 0x2FBA2E25;
+ /*
+ * The derived frequency is calculated as follows:
+ * (CTC_FREQ * msr[63:32]) >> 32 = target frequency.
+ * Back solve the multiplier so the 3.579545MHz ACPI timer
+ * frequency is used.
+ */
+ msr.hi = (3579545ULL << 32) / CTC_FREQ;
/* Set PM1 timer IO port and enable*/
msr.lo = EMULATE_PM_TMR_EN | (ACPI_PMIO_BASE + R_ACPI_PM1_TMR);
wrmsr(MSR_EMULATE_PM_TMR, msr);
diff --git a/src/soc/intel/apollolake/include/soc/cpu.h b/src/soc/intel/apollolake/include/soc/cpu.h
index b731d4f539..78fc0b0df6 100644
--- a/src/soc/intel/apollolake/include/soc/cpu.h
+++ b/src/soc/intel/apollolake/include/soc/cpu.h
@@ -37,4 +37,7 @@ void apollolake_init_cpus(struct device *dev);
#define BASE_CLOCK_MHZ 100
+/* Common Timer Copy (CTC) frequency - 19.2MHz. */
+#define CTC_FREQ 19200000
+
#endif /* _SOC_APOLLOLAKE_CPU_H_ */