[XS] Change in coreboot[main]: soc/mediatek/mt8196: Fix RTC recovery by disabling external XTAL

[Yidi Lin (Code Review)]

Yidi Lin has submitted this change. ( https://review.coreboot.org/c/coreboot/+/86353?usp=email )

Change subject: soc/mediatek/mt8196: Fix RTC recovery by disabling external XTAL
......................................................................

soc/mediatek/mt8196: Fix RTC recovery by disabling external XTAL

Configure PMIC register 0x50c bit0 which decides whether to use external
xtal. This bit of mt6685 should be set to 1, to disable external xtal.

BRANCH=rauru
BUG=b:395485005
TEST=emerge-rauru coreboot chromeos-bootimage, remove battery and
charger, then insert battery and charge, RTC boots normally.

Signed-off-by: Shunxi Zhang 
Change-Id: Iea44f13af030f24c02993dd43a35a9d8b4f72179
Reviewed-on: https://review.coreboot.org/c/coreboot/+/86353
Reviewed-by: Shunxi Zhang 
Tested-by: build bot (Jenkins) 
Reviewed-by: Yu-Ping Wu 
Reviewed-by: Yidi Lin 
---
M src/soc/mediatek/mt8196/mt6685_rtc.c
1 file changed, 4 insertions(+), 0 deletions(-)

Approvals:
  Yu-Ping Wu: Looks good to me, approved
  Yidi Lin: Looks good to me, approved
  build bot (Jenkins): Verified
  Shunxi Zhang: Looks good to me, but someone else must approve

diff --git a/src/soc/mediatek/mt8196/mt6685_rtc.c b/src/soc/mediatek/mt8196/mt6685_rtc.c
index 4564a31..4e63f10 100644
--- a/src/soc/mediatek/mt8196/mt6685_rtc.c
+++ b/src/soc/mediatek/mt8196/mt6685_rtc.c
@@ -345,6 +345,10 @@
 {
    printk(BIOS_INFO, "%s: enter\n", __func__);

+	config_interface(SCK_TOP_XTAL_SEL_ADDR, 1, SCK_TOP_XTAL_SEL_MASK,
+			 SCK_TOP_XTAL_SEL_SHIFT);
+	udelay(100);
+
    if (!retry(RECOVERY_RETRY_COUNT,
    	   rtc_frequency_meter_check() &&
    	   rtc_init_after_recovery())) {