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

[Hans de Goede]

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 <hdego...@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.rc1