soc/mediatek/mt8188: Support ARM arch timer

Use ARM architectual timer by initializing frequency to 13 MHz. Since
system timer is the source of the architectual timer, we also call
`timer_prepare` in `init_timer`.

BUG=b:229800119
TEST=run `suite:faft_bios` to verify the firmware stability.
     check timestamps by cbmem.

Cq-Depend: chromium:4747539
Change-Id: I8b1348044e4c92984510604b7f61611e13284d86
Signed-off-by: Yidi Lin <yidilin@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76919
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/mediatek/mt8188/Kconfig

@@ -13,6 +13,7 @@ config SOC_MEDIATEK_MT8188
 	select MEDIATEK_DRAM_BLOB_FAST_INIT
 	select USE_CBMEM_DRAM_INFO
 	select DPM_FOUR_CHANNEL
+	select ARM64_USE_ARCH_TIMER
 
 if SOC_MEDIATEK_MT8188
 

src/soc/mediatek/mt8188/Makefile.inc

@@ -6,7 +6,7 @@ all-y += ../common/gpio.c ../common/gpio_op.c gpio.c
 all-y += ../common/i2c.c i2c.c
 all-y += ../common/pll.c pll.c
 all-$(CONFIG_SPI_FLASH) += ../common/spi.c spi.c
-all-y += ../common/timer.c ../common/timer_prepare.c
+all-y += timer.c ../common/timer_prepare.c
 all-y += ../common/uart.c
 
 bootblock-y += bootblock.c

src/soc/mediatek/mt8188/timer.c

@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <arch/lib_helpers.h>
+#include <commonlib/helpers.h>
+#include <delay.h>
+#include <soc/addressmap.h>
+#include <soc/timer.h>
+
+static struct mtk_gpt_regs *const mtk_gpt = (void *)GPT_BASE;
+
+void init_timer(void)
+{
+	timer_prepare();
+
+	raw_write_cntfrq_el0(13 * MHz);
+
+	/* TODO: remove GPT timer init after DRAM blob switching to arch timer */
+	/* Disable timer and clear the counter */
+	clrbits32(&mtk_gpt->gpt6_con, GPT6_CON_EN);
+	setbits32(&mtk_gpt->gpt6_con, GPT6_CON_CLR);
+
+	/* Set clock source to system clock and set clock divider to 1 */
+	SET32_BITFIELDS(&GPT6_CLOCK_REG(mtk_gpt),
+			GPT6_CLK_CLK6, GPT6_CLK_CLK6_SYS,
+			GPT6_CLK_CLKDIV6, GPT6_CLK_CLKDIV_DIV1);
+	/* Set operation mode to FREERUN mode and enable timer */
+	SET32_BITFIELDS(&mtk_gpt->gpt6_con,
+			GPT6_CON_MODE6, GPT6_MODE_FREERUN,
+			GPT6_CON_EN6, GPT6_CON_EN);
+}