[PATCH] regulator: ltc3676: don't read the write-only HRST and CLIRQ registers

[Abhishek Ojha]

HRST (0x1e) and CLIRQ (0x1f) are write-only command strobes. Writing HRST
triggers a hard reset of the chip and writing CLIRQ clears the interrupt;
reading them returns nothing useful, and the read itself fires the command.

The result is that a plain register dump resets the board:

  cat /sys/kernel/debug/regmap/2-003c/registers

walks every readable register, hits HRST, and the board reboots.

Split the callback back in two so HRST and CLIRQ stay writable but are no
longer readable. The readable range is left unchanged
(LTC3676_BUCK1 ... LTC3676_IRQSTAT).

Fixes: 37b918a034fe ("regulator: Add LTC3676 support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Abhishek Ojha <Abhishek.ojha@xxxxxxxxxxxxxxxxxxxx>
---
 drivers/regulator/ltc3676.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/regulator/ltc3676.c b/drivers/regulator/ltc3676.c
index 307c6f7a155d..d67cee4e0be0 100644
--- a/drivers/regulator/ltc3676.c
+++ b/drivers/regulator/ltc3676.c
@@ -232,7 +232,7 @@ static const struct regulator_desc ltc3676_regulators[LTC3676_NUM_REGULATORS] =
 	LTC3676_FIXED_REG(LDO4, ldo4, LDOB, 2),
 };
 
-static bool ltc3676_readable_writeable_reg(struct device *dev, unsigned int reg)
+static bool ltc3676_writeable_reg(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
 	case LTC3676_BUCK1 ... LTC3676_IRQSTAT:
@@ -243,6 +243,15 @@ static bool ltc3676_readable_writeable_reg(struct device *dev, unsigned int reg)
 	return false;
 }
 
+static bool ltc3676_readable_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case LTC3676_BUCK1 ... LTC3676_IRQSTAT:
+		return true;
+	}
+	return false;
+}
+
 static bool ltc3676_volatile_reg(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
@@ -255,8 +264,8 @@ static bool ltc3676_volatile_reg(struct device *dev, unsigned int reg)
 static const struct regmap_config ltc3676_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
-	.writeable_reg = ltc3676_readable_writeable_reg,
-	.readable_reg = ltc3676_readable_writeable_reg,
+	.writeable_reg = ltc3676_writeable_reg,
+	.readable_reg = ltc3676_readable_reg,
 	.volatile_reg = ltc3676_volatile_reg,
 	.max_register = LTC3676_CLIRQ,
 	.use_single_read = true,
-- 
2.43.0