[PATCH v3] regulator: axp20x: Fix axp22x ldo_io registration error on cold boot

[Hans de Goede <hdegoede@redhat.com>]

The maximum supported voltage for ldo_io# is 3.3V, but on cold
boot the selector comes up at 0x1f, which maps to 3.8V.

This causes _regulator_get_voltage() to fail with -EINVAL which
causes regulator registration to fail when constrains are used:

[    1.467788] vcc-touchscreen: failed to get the current voltage(-22)
[    1.474209] axp20x-regulator axp20x-regulator: Failed to register ldo_io1
[    1.483363] axp20x-regulator: probe of axp20x-regulator failed with error -22

This commits makes the axp20x regulator driver accept the 0x1f register
value, fixing this.

The datasheet does not guarantee reliable operation above 3.3V, so on
boards where this regulator is used the regulator-max-microvolt setting
must be 3.3V or less.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v2:
-No changes (resend)
Changes in v3:
-Instead of overwriting the 0x1f register value even when the regulator
 is not used / not described in dt, accept 0x1f as a valid value and
 when the regulator is used rely on the constraints to ensure that
 a value in the supported output range gets used.
---
 drivers/regulator/axp20x-regulator.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/regulator/axp20x-regulator.c b/drivers/regulator/axp20x-regulator.c
index d0f8d10..2422ddd 100644
--- a/drivers/regulator/axp20x-regulator.c
+++ b/drivers/regulator/axp20x-regulator.c
@@ -219,10 +219,14 @@ static const struct regulator_desc axp22x_regulators[] = {
 		 AXP22X_ELDO2_V_OUT, 0x1f, AXP22X_PWR_OUT_CTRL2, BIT(1)),
 	AXP_DESC(AXP22X, ELDO3, "eldo3", "eldoin", 700, 3300, 100,
 		 AXP22X_ELDO3_V_OUT, 0x1f, AXP22X_PWR_OUT_CTRL2, BIT(2)),
-	AXP_DESC_IO(AXP22X, LDO_IO0, "ldo_io0", "ips", 700, 3300, 100,
+	/* Note the datasheet only guarantees reliable operation up to
+	 * 3.3V, this needs to be enforced via dts provided constraints */
+	AXP_DESC_IO(AXP22X, LDO_IO0, "ldo_io0", "ips", 700, 3800, 100,
 		    AXP22X_LDO_IO0_V_OUT, 0x1f, AXP20X_GPIO0_CTRL, 0x07,
 		    AXP22X_IO_ENABLED, AXP22X_IO_DISABLED),
-	AXP_DESC_IO(AXP22X, LDO_IO1, "ldo_io1", "ips", 700, 3300, 100,
+	/* Note the datasheet only guarantees reliable operation up to
+	 * 3.3V, this needs to be enforced via dts provided constraints */
+	AXP_DESC_IO(AXP22X, LDO_IO1, "ldo_io1", "ips", 700, 3800, 100,
 		    AXP22X_LDO_IO1_V_OUT, 0x1f, AXP20X_GPIO1_CTRL, 0x07,
 		    AXP22X_IO_ENABLED, AXP22X_IO_DISABLED),
 	AXP_DESC_FIXED(AXP22X, RTC_LDO, "rtc_ldo", "ips", 3000),
-- 
2.7.4