On Mon, Mar 18, 2019 at 07:51:55AM -0700, Guenter Roeck wrote:
> On 3/18/19 7:29 AM, Samu Nuutamo wrote:
> > When tsi-as-adc is configured it is possible for in7[0123]_input read to
>
> in{70,71,72,73}_input ?
>
Yes, and by that I meant the files inside /sys/class/hwmon/hwmon0. The
race can be triggered by reading both tsi and adc values (in70-73,
in4-6) concurrently, while verifying that the values are as expected.
Using a simple test script that read the values continuously I got
incorrect readings once every few minutes.
> > return an incorrect value if a concurrent read to in[456]_input is
> > performed. This is likely caused by a concurrent manipulation of the mux
> > channel without proper locking as hwmon and mfd use different locks for
> > synchronization.
> >
> > Switch hwmon to use the same lock as mfd when accessing the TSI channel.
> >
> > Fixes: 4f16cab19a3d5 ("hwmon: da9052: Add support for TSI channel")
> > Signed-off-by: Samu Nuutamo <[email protected]>
> > ---
> > drivers/hwmon/da9052-hwmon.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/hwmon/da9052-hwmon.c b/drivers/hwmon/da9052-hwmon.c
> > index 8ec5bf4ce392..af136a638065 100644
> > --- a/drivers/hwmon/da9052-hwmon.c
> > +++ b/drivers/hwmon/da9052-hwmon.c
> > @@ -249,9 +249,9 @@ static ssize_t da9052_tsi_show(struct device *dev,
> > int channel = to_sensor_dev_attr(devattr)->index;
> > int ret;
> > - mutex_lock(&hwmon->hwmon_lock);
> > + mutex_lock(&hwmon->da9052->auxadc_lock);
>
> This is, at best, a kludge.
>
> The hwmon driver doesn't own struct da9052 and should not really access any
> of its
> structure members. The problem suggests that __da9052_read_tsi() should have
> been implemented in the mfd core, similar to da9052_adc_manual_read().
>
Not sure if I have resources to do a proper fix at this point.
- Samu
