When we set or clear a pmic_bus bit, we do a read-modify-write

operation. We waste some time however, by writing back the exact same
value that was already set in the chip. Let us thus only configure the
chip if the data is different.

arch/arm/mach-sunxi/pmic_bus.c

@@ -101,6 +101,9 @@ int pmic_bus_setbits(u8 reg, u8 bits)
 	if (ret)
 		return ret;
 
+	if (val & bits)
+		return 0;
+
 	val |= bits;
 	return pmic_bus_write(reg, val);
 }
@@ -114,6 +117,9 @@ int pmic_bus_clrbits(u8 reg, u8 bits)
 	if (ret)
 		return ret;
 
+	if (!(val & bits))
+		return 0;
+
 	val &= ~bits;
 	return pmic_bus_write(reg, val);
 }