[PATCH v2 07/13] power: bq24257: Extend scope of mutex protection

Andreas Dannenberg
2015-09-09T00:12:31Z

This commit extends the use of the existing mutex to pave the way for
using direct device access inside sysfs getter/setter routines in a
way that the access during interrupts and timer routines does not
interfere with device access by the CPU or between multiple cores.

This also addresses a potential race condition that could be caused
by bq24257_irq_handler_thread() and bq24257_iilimit_autoset() accessing
the device simultaneously.

Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
---
drivers/power/bq24257_charger.c | 60 ++++++++++++++++++++++++-----------------
1 file changed, 35 insertions(+), 25 deletions(-)

diff --git a/drivers/power/bq24257_charger.c b/drivers/power/bq24257_charger.c
index c160fde..f0d4307 100644
--- a/drivers/power/bq24257_charger.c
+++ b/drivers/power/bq24257_charger.c
@@ -102,7 +102,7 @@ struct bq24257_device {
struct bq24257_init_data init_data;
struct bq24257_state state;

- struct mutex lock; /* protect state data */
+ struct mutex lock; /* protect device access and state data */

bool in_ilimit_autoset_disable;
bool pg_gpio_disable;
@@ -271,10 +271,10 @@ static int bq24257_power_supply_get_property(struct power_supply *psy,
{
struct bq24257_device *bq = power_supply_get_drvdata(psy);
struct bq24257_state state;
+ int ret = 0;

mutex_lock(&bq->lock);
state = bq->state;
- mutex_unlock(&bq->lock);

switch (psp) {
case POWER_SUPPLY_PROP_STATUS:
@@ -350,10 +350,12 @@ static int bq24257_power_supply_get_property(struct power_supply *psy,
break;

default:
- return -EINVAL;
+ ret = -EINVAL;
}

- return 0;
+ mutex_unlock(&bq->lock);
+
+ return ret;
}

static int bq24257_get_chip_state(struct bq24257_device *bq,
@@ -400,15 +402,9 @@ static int bq24257_get_chip_state(struct bq24257_device *bq,
static bool bq24257_state_changed(struct bq24257_device *bq,
struct bq24257_state *new_state)
{
- int ret;
-
- mutex_lock(&bq->lock);
- ret = (bq->state.status != new_state->status ||
- bq->state.fault != new_state->fault ||
- bq->state.power_good != new_state->power_good);
- mutex_unlock(&bq->lock);
-
- return ret;
+ return bq->state.status != new_state->status ||
+ bq->state.fault != new_state->fault ||
+ bq->state.power_good != new_state->power_good;
}

enum bq24257_loop_status {
@@ -531,7 +527,9 @@ static void bq24257_iilimit_setup_work(struct work_struct *work)
struct bq24257_device *bq = container_of(work, struct bq24257_device,
iilimit_setup_work.work);

+ mutex_lock(&bq->lock);
bq24257_iilimit_autoset(bq);
+ mutex_unlock(&bq->lock);
}

static void bq24257_handle_state_change(struct bq24257_device *bq,
@@ -542,9 +540,7 @@ static void bq24257_handle_state_change(struct bq24257_device *bq,
bool reset_iilimit = false;
bool config_iilimit = false;

- mutex_lock(&bq->lock);
old_state = bq->state;
- mutex_unlock(&bq->lock);

/*
* Handle BQ2425x state changes observing whether the D+/D- based input
@@ -599,25 +595,30 @@ static irqreturn_t bq24257_irq_handler_thread(int irq, void *private)
struct bq24257_device *bq = private;
struct bq24257_state state;

+ mutex_lock(&bq->lock);
+
ret = bq24257_get_chip_state(bq, &state);
if (ret < 0)
- return IRQ_HANDLED;
+ goto out;

if (!bq24257_state_changed(bq, &state))
- return IRQ_HANDLED;
+ goto out;

dev_dbg(bq->dev, "irq(state changed): status/fault/pg = %d/%d/%d\n",
state.status, state.fault, state.power_good);

bq24257_handle_state_change(bq, &state);
-
- mutex_lock(&bq->lock);
bq->state = state;
+
mutex_unlock(&bq->lock);

power_supply_changed(bq->charger);

return IRQ_HANDLED;
+
+out:
+ mutex_unlock(&bq->lock);
+ return IRQ_HANDLED;
}

static int bq24257_hw_init(struct bq24257_device *bq)
@@ -657,9 +658,7 @@ static int bq24257_hw_init(struct bq24257_device *bq)
if (ret < 0)
return ret;

- mutex_lock(&bq->lock);
bq->state = state;
- mutex_unlock(&bq->lock);

if (bq->in_ilimit_autoset_disable) {
dev_dbg(bq->dev, "manually setting iilimit = %d\n",
@@ -1018,11 +1017,15 @@ static int bq24257_suspend(struct device *dev)
if (!bq->in_ilimit_autoset_disable)
cancel_delayed_work_sync(&bq->iilimit_setup_work);

+ mutex_lock(&bq->lock);
+
/* reset all registers to default (and activate standalone mode) */
ret = bq24257_field_write(bq, F_RESET, 1);
if (ret < 0)
dev_err(bq->dev, "Cannot reset chip to standalone mode.\n");

+ mutex_unlock(&bq->lock);
+
return ret;
}

@@ -1031,24 +1034,31 @@ static int bq24257_resume(struct device *dev)
int ret;
struct bq24257_device *bq = dev_get_drvdata(dev);

+ mutex_lock(&bq->lock);
+
ret = regcache_drop_region(bq->rmap, BQ24257_REG_1, BQ24257_REG_7);
if (ret < 0)
- return ret;
+ goto err;

ret = bq24257_field_write(bq, F_RESET, 0);
if (ret < 0)
- return ret;
+ goto err;

ret = bq24257_hw_init(bq);
if (ret < 0) {
dev_err(bq->dev, "Cannot init chip after resume.\n");
- return ret;
+ goto err;
}

+ mutex_unlock(&bq->lock);
+
/* signal userspace, maybe state changed while suspended */
power_supply_changed(bq->charger);
-
return 0;
+
+err:
+ mutex_unlock(&bq->lock);
+ return ret;
}
#endif

--
1.9.1