Re: [PATCH] hwmon: da9052: Synchronize access with mfd

[Guenter Roeck]

On 5/11/20 4:02 AM, Sebastian Reichel wrote:
> From: Samu Nuutamo <samu.nuutamo@xxxxxxxxx>
> 
> When tsi-as-adc is configured it is possible for in7[0123]_input read to
> return an incorrect value if a concurrent read to in[456]_input is
> performed. This is 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 <samu.nuutamo@xxxxxxxxx>
> [rebase to current master, reword commit message slightly]
> Signed-off-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>

Have you explored calling da9052_adc_manual_read() instead ?
At the very least we should have a comment explaining why that
isn't feasible.

Thanks,
Guenter

> ---
>  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 53b517dbe7e6..4af2fc309c28 100644
> --- a/drivers/hwmon/da9052-hwmon.c
> +++ b/drivers/hwmon/da9052-hwmon.c
> @@ -244,9 +244,9 @@ 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);
>  	ret = __da9052_read_tsi(dev, channel);
> -	mutex_unlock(&hwmon->hwmon_lock);
> +	mutex_unlock(&hwmon->da9052->auxadc_lock);
>  
>  	if (ret < 0)
>  		return ret;
>