From bea930d7e483e777b3b7ed88632b030a31d1dc4b Mon Sep 17 00:00:00 2001 From: Aaron Durbin Date: Wed, 18 May 2016 11:08:39 -0500 Subject: soc/intel/apollolake: clear up ACPI timer emulation magic constant The timer emulation works by deriving a frequency based off the Common Timer Copy with a frequency of 19.2MHz. The desired frequency = (19.2MHz * multiplier) >> 32; With that knowledge update the code to let the compiler perform the necessary math based on target frequency. Change-Id: I716c7980f0456a7c6072bbaaddd6b7fcd8cd5b37 Signed-off-by: Aaron Durbin Reviewed-on: https://review.coreboot.org/14889 Tested-by: build bot (Jenkins) Reviewed-by: Furquan Shaikh Reviewed-by: Andrey Petrov Reviewed-by: Paul Menzel --- src/soc/intel/apollolake/bootblock/bootblock.c | 9 +++++++-- src/soc/intel/apollolake/include/soc/cpu.h | 3 +++ 2 files changed, 10 insertions(+), 2 deletions(-) (limited to 'src/soc/intel/apollolake') 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_ */ -- cgit v1.2.3