[PATCH] regulator: mt6358: use regmap helper to read fixed LDO calibration

[Daniel Golle <daniel@makrotopia.org>]

The "fixed" LDOs with output voltage calibration use
mt6358_get_buck_voltage_sel as their get_voltage_sel op, but the
MT6358_REG_FIXED and MT6366_REG_FIXED entries do not populate
da_vsel_reg/da_vsel_mask. The op therefore reads register 0x0 with a
zero mask and shifts the result by ffs(0) - 1 = -1, which is undefined
behaviour and gets flagged by UBSAN on every boot on MT6366 boards:

  UBSAN: shift-out-of-bounds in drivers/regulator/mt6358-regulator.c:384:38
  shift exponent -1 is negative
  Call trace:
   mt6358_get_buck_voltage_sel+0xc8/0x120
   regulator_get_voltage_rdev+0x70/0x170
   set_machine_constraints+0x504/0xc38
   regulator_register+0x324/0xc68

Besides the undefined shift, the returned selector is always 0, so the
actual calibration offset programmed in <reg>_ANA_CON0 is never
reported.

The descriptor already carries the correct vsel_reg/vsel_mask (the
ANA_CON0 calibration field), matching the regulator_set_voltage_sel_regmap
op already in use. Read the selector back through
regulator_get_voltage_sel_regmap instead.

Fixes: cf08fa74c716 ("regulator: mt6358: Add output voltage fine tuning to fixed regulators")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 drivers/regulator/mt6358-regulator.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/regulator/mt6358-regulator.c b/drivers/regulator/mt6358-regulator.c
index f2bb3c1523ca..d6a0ec406b07 100644
--- a/drivers/regulator/mt6358-regulator.c
+++ b/drivers/regulator/mt6358-regulator.c
@@ -492,7 +492,7 @@ static const struct regulator_ops mt6358_volt_fixed_ops = {
 	.list_voltage = regulator_list_voltage_linear,
 	.map_voltage = regulator_map_voltage_linear,
 	.set_voltage_sel = regulator_set_voltage_sel_regmap,
-	.get_voltage_sel = mt6358_get_buck_voltage_sel,
+	.get_voltage_sel = regulator_get_voltage_sel_regmap,
 	.set_voltage_time_sel = regulator_set_voltage_time_sel,
 	.enable = regulator_enable_regmap,
 	.disable = regulator_disable_regmap,
-- 
2.55.0