board: phytec: phycore_am68x: Turn off pmic watchdog

Starting with pmic firmware version 5 the watchdog is enabled with a
timeout window of 13 minutes by default.

The TI EVMs use a dip switch to control a gpio on the pmic which gets
configured as DISABLE_WDOG by the firmware.
On the phycore_am68x there is no such dip switch so pull resistors would be
necessary. Using mcu_i2c0 to turn off the pmic watchdog works with all
hardware and pmic firmware combinations.

Signed-off-by: Dominik Haller <d.haller@phytec.de>

board/phytec/phycore_am68x/phycore-am68x.c

@@ -21,6 +21,7 @@
 #include <dm/uclass-internal.h>
 #include <dm/root.h>
 #include <asm/arch/k3-ddr.h>
+#include <i2c.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -69,6 +70,46 @@ void spl_perform_board_fixups(struct spl_image_info *spl_image)
 }
 #endif
 
+#define TPS6594_I2C_WD_ADDR	0x12
+#define WD_THR_CFG_REG		0x09
+#define WD_EN			BIT(6)
+
+int tps6594_disable_watchdog(void)
+{
+	struct udevice *i2c_bus, *i2c_dev;
+	int ret;
+	u8 val;
+
+	ret = uclass_get_device_by_name(UCLASS_I2C, "i2c@40b00000", &i2c_bus);
+	if (ret)
+		return ret;
+
+	ret = dm_i2c_probe(i2c_bus, TPS6594_I2C_WD_ADDR, 0, &i2c_dev);
+	if (ret)
+		return ret;
+
+	ret = dm_i2c_reg_read(i2c_dev, WD_THR_CFG_REG);
+	if (ret < 0)
+		return ret;
+
+	val = (u8)ret;
+	val &= ~WD_EN;
+	ret = dm_i2c_reg_write(i2c_dev, WD_THR_CFG_REG, val);
+
+	return ret;
+}
+
+int board_init(void)
+{
+	int ret;
+
+	ret = tps6594_disable_watchdog();
+	if (ret)
+		printf("disabling TPS6594 watchdog failed: %d\n", ret);
+
+	return 0;
+}
+
 void spl_board_init(void)
 {
 	struct udevice *dev;

configs/phycore_am68x_a72_defconfig

@@ -38,7 +38,6 @@ CONFIG_OF_SYSTEM_SETUP=y
 CONFIG_BOOTCOMMAND="bootflow scan -lb; run ${boot}boot"
 CONFIG_DEFAULT_FDT_FILE="oftree"
 CONFIG_LOGLEVEL=7
-# CONFIG_BOARD_INIT is not set
 CONFIG_SPL_MAX_SIZE=0xc0000
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_SYS_MALLOC_SIMPLE=y