mediatek/mt8183: postpone dcxo low power mode setting

Consider the association between modem[1] and DCXO, this patch is a fix for
eb5e47d("mediatek/mt8183: update dcxo output buffer setting") [2]
We should not disable XO_CEL and block the bblpm request when modem is still ON.
For power-saving, we still could disable unused XO_CEL and
mask request to disable unused power mode when modem is no longer be used.

[1] https://review.coreboot.org/c/coreboot/+/32666
[2] https://review.coreboot.org/c/coreboot/+/32323

BRANCH=none
TEST=Boots correctly on Krane.

Change-Id: I047ebed615e874977ca211aafd52b5551c71b764
Signed-off-by: Weiyi Lu <weiyi.lu@mediatek.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34777
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>

src/soc/mediatek/mt8183/include/soc/rtc.h

@@ -147,6 +147,7 @@ enum {
 /* PMIC DCXO Register Definition */
 enum {
 	PMIC_RG_DCXO_CW00 = 0x0788,
+	PMIC_RG_DCXO_CW00_CLR = 0x078C,
 	PMIC_RG_DCXO_CW02 = 0x0790,
 	PMIC_RG_DCXO_CW07 = 0x079A,
 	PMIC_RG_DCXO_CW09 = 0x079E,
@@ -218,5 +219,6 @@ void rtc_bbpu_power_on(void);
 void rtc_osc_init(void);
 int rtc_init(u8 recover);
 void rtc_boot(void);
+void mt6358_dcxo_disable_unused(void);
 
 #endif /* SOC_MEDIATEK_MT8183_RTC_H */

src/soc/mediatek/mt8183/rtc.c

@@ -411,10 +411,9 @@ static void dcxo_init(void)
 	rtc_write(PMIC_RG_DCXO_CW16, 0x9855);
 
 	/* 26M enable control */
-	/* Enable clock buffer XO_SOC */
-	rtc_write(PMIC_RG_DCXO_CW00, 0x4005);
+	/* Enable clock buffer XO_SOC, XO_CEL */
+	rtc_write(PMIC_RG_DCXO_CW00, 0x4805);
 	rtc_write(PMIC_RG_DCXO_CW11, 0x8000);
-	rtc_write(PMIC_RG_DCXO_CW23, 0x0053);
 
 	/* Load thermal coefficient */
 	rtc_write(PMIC_RG_TOP_TMA_KEY, 0x9CA7);
@@ -432,6 +431,14 @@ static void dcxo_init(void)
 	mdelay(5);
 }
 
+void mt6358_dcxo_disable_unused(void)
+{
+	/* Disable clock buffer XO_CEL */
+	rtc_write(PMIC_RG_DCXO_CW00_CLR, 0x0800);
+	/* Mask bblpm */
+	rtc_write(PMIC_RG_DCXO_CW23, 0x0053);
+}
+
 /* the rtc boot flow entry */
 void rtc_boot(void)
 {

src/soc/mediatek/mt8183/soc.c

@@ -17,6 +17,7 @@
 #include <soc/emi.h>
 #include <soc/md_ctrl.h>
 #include <soc/mmu_operations.h>
+#include <soc/rtc.h>
 #include <soc/sspm.h>
 #include <symbols.h>
 
@@ -29,6 +30,7 @@ static void soc_init(struct device *dev)
 {
 	mtk_mmu_disable_l2c_sram();
 	mtk_md_early_init();
+	mt6358_dcxo_disable_unused();
 	sspm_init();
 }