[PATCH 1/2] regulator: mt6363: Use 8-bit regmap values

[GIBEOM LEE (이기범)]

The registers of the MT6363 are 8 bits wide, but the regmap has 16-bit
values. On SPMI that makes every access two bytes long: a read also returns
the next register in the upper byte, and a write also writes the next
register, with 0 or with what a read-modify-write found there.

The next register is rarely related to the one the driver means, so this
goes wrong in several places:

 - mt6363_vreg_disable_setclr() writes the mask to the CLR register and 0
   to the one after it. For VS2 and VBUCK1-7 that is the enable register of
   VS1, VS3 and VSRAM_{DIGRF,MDFE,MODEM}, so disabling any of them disables
   those five as well. For those five it is the low power register of VS2
   and VBUCK1-7.
 - mt6363_regulator_set_load() zeroes the register after OP_CFG and the one
   after the third OP_EN register.
 - A read-modify-write of the low power register of a buck writes back to
   its SET register what it read from it. If SET reads like the register
   itself, that sets again the bit that was just cleared.
 - TOP_TRAP is read together with MISC_TOP_INT_CON0, so the VEMC voltage
   callbacks fail with -EINVAL once a MISC interrupt is enabled.
 - regmap_bulk_write() takes a number of registers. The sizeof() of the u16
   keys of TMA and BUCK_TOP asks for two 16-bit registers, so it reads past
   the key on the stack and writes that to the two registers after the key.

MediaTek's regulator driver uses the regmap of their MFD driver, which has
8-bit values (mt6363-regulator.c and mtk-spmi-pmic.c in the OnePlus MT6897
kernel, OnePlusOSS android_kernel_modules_and_devicetree_oneplus_mt6897,
branch oneplus/mt6897_b_16.0.0_oneplus_pad). With 8-bit values one access
is one register, and the sizeof() of the keys is the right number of
registers.

Fixes: 3c36965df808 ("regulator: Add support for MediaTek MT6363 SPMI PMIC Regulators")
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: GIBEOM LEE (이기범) <rtx4060@xxxxxxxxx>
---
 drivers/regulator/mt6363-regulator.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/regulator/mt6363-regulator.c b/drivers/regulator/mt6363-regulator.c
index aa6a8eb..cc2e841 100644
--- a/drivers/regulator/mt6363-regulator.c
+++ b/drivers/regulator/mt6363-regulator.c
@@ -811,7 +811,7 @@ static struct regmap *mt6363_spmi_register_regmap(struct device *dev)
 {
 	struct regmap_config mt6363_regmap_config = {
 		.reg_bits = 16,
-		.val_bits = 16,
+		.val_bits = 8,
 		.max_register = 0x1f90,
 		.fast_io = true,
 	};