allwinner: Return the PMIC to I2C mode after use

This gives the rich OS the flexibility to choose between I2C and RSB
communication. Since a runtime address can only be assigned once after
entering RSB mode, it also lets the rich OS choose any runtime address.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Change-Id: Id49c124c5e925985fc31c0ba38c7fb6c941aafa8

include/drivers/allwinner/axp.h

@@ -9,6 +9,10 @@
 
 #include <stdint.h>
 
+#define AXP20X_MODE_REG 0x3e
+#define AXP20X_MODE_I2C 0x00
+#define AXP20X_MODE_RSB 0x7c
+
 #define NA 0xff
 
 enum {

plat/allwinner/sun50i_a64/sunxi_power.c

@@ -97,11 +97,8 @@ static int rsb_init(void)
 	if (ret)
 		return ret;
 
-	/*
-	 * Initiate an I2C transaction to write 0x7c into register 0x3e,
-	 * switching the PMIC to RSB mode.
-	 */
-	ret = rsb_set_device_mode(0x7c3e00);
+	/* Initiate an I2C transaction to switch the PMIC to RSB mode. */
+	ret = rsb_set_device_mode(AXP20X_MODE_RSB << 16 | AXP20X_MODE_REG << 8);
 	if (ret)
 		return ret;
 
@@ -151,6 +148,11 @@ int sunxi_pmic_setup(uint16_t socid, const void *fdt)
 		pmic = AXP803_RSB;
 		axp_setup_regulators(fdt);
 
+		/* Switch the PMIC back to I2C mode. */
+		ret = axp_write(AXP20X_MODE_REG, AXP20X_MODE_I2C);
+		if (ret)
+			return ret;
+
 		break;
 	default:
 		return -ENODEV;