power: supply: sbs-battery: Prevent CAPACITY_MODE races

A subset of smart battery commands return charge or energy depending on
the CAPACITY_MODE bit setting of BatteryMode(). In order to
unambiguously read a charge or energy value, it is necessary to ensure
that CAPACITY_MODE is set as desired, and not changed for the duration
of the attribute read.

Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>

diff --git a/drivers/power/supply/sbs-battery.c b/drivers/power/supply/sbs-battery.c
index cf43e38a9443923610f9a1e8370fa9d4f48a2d56..cdc1d71909a5e54899552a3fdb436b1aee8e40f6 100644 (file)
--- a/drivers/power/supply/sbs-battery.c
+++ b/drivers/power/supply/sbs-battery.c
@@ -171,6 +171,7 @@ struct sbs_info {
        u32                             i2c_retry_count;
        u32                             poll_retry_count;
        struct delayed_work             work;
+       struct mutex                    mode_lock;
 };
 
 static char model_name[I2C_SMBUS_BLOCK_MAX + 1];
@@ -622,7 +623,13 @@ static int sbs_get_property(struct power_supply *psy,
                if (ret < 0)
                        break;
 
+               /* sbs_get_battery_capacity() will change the battery mode
+                * temporarily to read the requested attribute. Ensure we stay
+                * in the desired mode for the duration of the attribute read.
+                */
+               mutex_lock(&chip->mode_lock);
                ret = sbs_get_battery_capacity(client, ret, psp, val);
+               mutex_unlock(&chip->mode_lock);
                break;
 
        case POWER_SUPPLY_PROP_SERIAL_NUMBER:
@@ -807,6 +814,7 @@ static int sbs_probe(struct i2c_client *client,
        psy_cfg.of_node = client->dev.of_node;
        psy_cfg.drv_data = chip;
        chip->last_state = POWER_SUPPLY_STATUS_UNKNOWN;
+       mutex_init(&chip->mode_lock);
 
        /* use pdata if available, fall back to DT properties,
         * or hardcoded defaults if not