[PATCH v3 2/3] ACPI / PMIC: xpower: Block P-Unit I2C access during read-modify-write

Hans de Goede
2018-10-11T14:29:51Z

intel_xpower_pmic_update_power() does a read-modify-write of the output
control register. The i2c-designware code blocks the P-Unit I2C access
during the read and write by taking the P-Unit's PMIC bus semaphore.
But between the read and the write that semaphore is released and the
P-Unit could make changes to the register which we then end up overwriting.

This commit makes intel_xpower_pmic_update_power() take the semaphore
itself so that it is held over the entire read-modify-write, avoiding this
race.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
drivers/acpi/pmic/intel_pmic_xpower.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/acpi/pmic/intel_pmic_xpower.c b/drivers/acpi/pmic/intel_pmic_xpower.c
index 316e55174aa9..9e6ddf2a2d4e 100644
--- a/drivers/acpi/pmic/intel_pmic_xpower.c
+++ b/drivers/acpi/pmic/intel_pmic_xpower.c
@@ -18,6 +18,7 @@
#include <linux/mfd/axp20x.h>
#include <linux/regmap.h>
#include <linux/platform_device.h>
+#include <asm/iosf_mbi.h>
#include "intel_pmic.h"

#define XPOWER_GPADC_LOW 0x5b
@@ -180,15 +181,21 @@ static int intel_xpower_pmic_get_power(struct regmap *regmap, int reg,
static int intel_xpower_pmic_update_power(struct regmap *regmap, int reg,
int bit, bool on)
{
- int data;
+ int data, ret;

/* GPIO1 LDO regulator needs special handling */
if (reg == XPOWER_GPI1_CTRL)
return regmap_update_bits(regmap, reg, GPI1_LDO_MASK,
on ? GPI1_LDO_ON : GPI1_LDO_OFF);

- if (regmap_read(regmap, reg, &data))
- return -EIO;
+ ret = iosf_mbi_block_punit_i2c_access();
+ if (ret)
+ return ret;
+
+ if (regmap_read(regmap, reg, &data)) {
+ ret = -EIO;
+ goto out;
+ }

if (on)
data |= BIT(bit);
@@ -196,9 +203,11 @@ static int intel_xpower_pmic_update_power(struct regmap *regmap, int reg,
data &= ~BIT(bit);

if (regmap_write(regmap, reg, data))
- return -EIO;
+ ret = -EIO;
+out:
+ iosf_mbi_unblock_punit_i2c_access();

- return 0;
+ return ret;
}

/**
--
2.19.0