soc/intel/tigerlake: Add definition for PMC EPOC

The PMC EPOC register indicates which external crystal oscillator is
connected to the PCH.  This frequency is important for determining the
IP clock of internal PCH devices.

Add definitions that allow this register to be read and extract the
crystal frequency, and a helper function to extract and return this
as the defined enum.

BUG=b:146482091

Signed-off-by: Duncan Laurie <dlaurie@google.com>
Change-Id: I959fe507f3dbf93b6176b333a9e725ed09f56328
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40887
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/soc/intel/tigerlake/pmc.c b/src/soc/intel/tigerlake/pmc.c
index 2d30424cd0..62e37114f3 100644
--- a/src/soc/intel/tigerlake/pmc.c
+++ b/src/soc/intel/tigerlake/pmc.c
@@ -17,6 +17,13 @@
 #include <soc/pm.h>
 #include <soc/soc_chip.h>
 
+enum pch_pmc_xtal pmc_get_xtal_freq(void)
+{
+	uint8_t *const pmcbase = pmc_mmio_regs();
+
+	return PCH_EPOC_XTAL_FREQ(read32(pmcbase + PCH_PMC_EPOC));
+}
+
 static void config_deep_sX(uint32_t offset, uint32_t mask, int sx, int enable)
 {
 	uint32_t reg;