allwinner: power: fix DRIVEVBUS pin setup

The DRIVEVBUS pin setup was broken in two ways:
- To configure this pin as an output pin, one has to *clear* the bit in
  register 0x8f. It is 0 by default, but rebooting from Linux might have
  left this bit set.
- Doing this just configures the pin as an output pin, but doesn't
  actually drive power to it. This is done via bit 2 in register 0x30.

Fix the routine to both properly configure the pin and drive power to
it. Add an axp_clrsetbits() helper on the way.

Now this isn't really perfect, still:
We only need to setup the PMIC power rails that are needed for U-Boot.
DRIVEVBUS typically controls the VBUS voltage for the host function of
an USB-OTG port, something we typically don't want in U-Boot (fastboot,
using the USB *device* functionality, is much more common). The
BananaPi-M64 uses the regulator in this way, but the Remix Mini PC
actually controls the power of both its USB ports via this line.

Technically we should differentiate here: if DRIVEVBUS controls a
microUSB-B socket, the power should stay off, any host-type A sockets
should be supplied, though.
For now just always enable the power, that shouldn't really hurt the
USB-OTG functionality anyway.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

plat/allwinner/sun50i_a64/sunxi_power.c

@@ -118,7 +118,7 @@ static int axp_write(uint8_t reg, uint8_t val)
 	return rsb_write(AXP803_RT_ADDR, reg, val);
 }
 
-static int axp_setbits(uint8_t reg, uint8_t set_mask)
+static int axp_clrsetbits(uint8_t reg, uint8_t clr_mask, uint8_t set_mask)
 {
 	uint8_t regval;
 	int ret;
@@ -127,11 +127,14 @@ static int axp_setbits(uint8_t reg, uint8_t set_mask)
 	if (ret < 0)
 		return ret;
 
-	regval = ret | set_mask;
+	regval = (ret & ~clr_mask) | set_mask;
 
 	return rsb_write(AXP803_RT_ADDR, reg, regval);
 }
 
+#define axp_clrbits(reg, clr_mask) axp_clrsetbits(reg, clr_mask, 0)
+#define axp_setbits(reg, set_mask) axp_clrsetbits(reg, 0, set_mask)
+
 static bool should_enable_regulator(const void *fdt, int node)
 {
 	if (fdt_getprop(fdt, node, "phandle", NULL) != NULL)
@@ -226,8 +229,11 @@ static void setup_axp803_rails(const void *fdt)
 		return;
 	}
 
-	if (fdt_getprop(fdt, node, "x-powers,drive-vbus-en", NULL))
-		axp_setbits(0x8f, BIT(4));
+	if (fdt_getprop(fdt, node, "x-powers,drive-vbus-en", NULL)) {
+		axp_clrbits(0x8f, BIT(4));
+		axp_setbits(0x30, BIT(2));
+		INFO("PMIC: AXP803: Enabling DRIVEVBUS\n");
+	}
 
 	/* descend into the "regulators" subnode */
 	node = fdt_first_subnode(fdt, node);