twl4030: fix potential power supply handling issues

twl4030_pmrecv_vsel_cfg currently first sets up device group (effectively
enabling the supply), and only then sets vsel (selects voltage). This could
lead to wrong voltage for a short time, or even long time if second i2c
write fails.

Fix this by writing vsel first and device group after that. Also
introduce error checking to not enable the supply if we failed to set
the voltage, and start logging errors as power supply problems are
usually important.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>

drivers/power/twl4030.c

@@ -65,13 +65,23 @@ void twl4030_power_reset_init(void)
 void twl4030_pmrecv_vsel_cfg(u8 vsel_reg, u8 vsel_val,
 				u8 dev_grp, u8 dev_grp_sel)
 {
-	/* Select the Device Group */
-	twl4030_i2c_write_u8(TWL4030_CHIP_PM_RECEIVER, dev_grp_sel,
-				dev_grp);
+	int ret;
 
 	/* Select the Voltage */
-	twl4030_i2c_write_u8(TWL4030_CHIP_PM_RECEIVER, vsel_val,
+	ret = twl4030_i2c_write_u8(TWL4030_CHIP_PM_RECEIVER, vsel_val,
 				vsel_reg);
+	if (ret != 0) {
+		printf("Could could not write vsel to reg %02x (%d)\n",
+			vsel_reg, ret);
+		return;
+	}
+
+	/* Select the Device Group (enable the supply if dev_grp_sel != 0) */
+	ret = twl4030_i2c_write_u8(TWL4030_CHIP_PM_RECEIVER, dev_grp_sel,
+				dev_grp);
+	if (ret != 0)
+		printf("Could could not write grp_sel to reg %02x (%d)\n",
+			dev_grp, ret);
 }
 
 void twl4030_power_init(void)