linux-kernel - Re: [PATCH v1 1/1] drivers/hwmon/pmbus: Add mutex to regulator ops

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Date:   Sun, 27 Feb 2022 08:47:04 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Marcello Sylvester Bauer <sylv@...v.io>
Cc:     Jean Delvare <jdelvare@...e.com>, linux-kernel@...r.kernel.org,
        linux-hwmon@...r.kernel.org,
        Patrick Rudolph <patrick.rudolph@...ements.com>
Subject: Re: [PATCH v1 1/1] drivers/hwmon/pmbus: Add mutex to regulator ops

On Fri, Feb 25, 2022 at 05:06:09PM +0100, Marcello Sylvester Bauer wrote:
> From: Patrick Rudolph <patrick.rudolph@...ements.com>
> 
> On PMBUS devices with multiple pages, the regulator ops need to be
> protected with the update mutex. This prevents accidentally changing
> the page in a separate thread while operating on the PMBUS_OPERATION
> register.
> 
> Tested on Infineon xdpe11280 while a separate thread polls for sensor
> data.
> 
> Signed-off-by: Patrick Rudolph <patrick.rudolph@...ements.com>
> Signed-off-by: Marcello Sylvester Bauer <sylv@...v.io>

Good catch. Applied.

Thanks,
Guenter

> ---
>  drivers/hwmon/pmbus/pmbus_core.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index 776ee2237be2..f79930162256 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -2386,10 +2386,14 @@ static int pmbus_regulator_is_enabled(struct regulator_dev *rdev)
>  {
>  	struct device *dev = rdev_get_dev(rdev);
>  	struct i2c_client *client = to_i2c_client(dev->parent);
> +	struct pmbus_data *data = i2c_get_clientdata(client);
>  	u8 page = rdev_get_id(rdev);
>  	int ret;
>  
> +	mutex_lock(&data->update_lock);
>  	ret = pmbus_read_byte_data(client, page, PMBUS_OPERATION);
> +	mutex_unlock(&data->update_lock);
> +
>  	if (ret < 0)
>  		return ret;
>  
> @@ -2400,11 +2404,17 @@ static int _pmbus_regulator_on_off(struct regulator_dev *rdev, bool enable)
>  {
>  	struct device *dev = rdev_get_dev(rdev);
>  	struct i2c_client *client = to_i2c_client(dev->parent);
> +	struct pmbus_data *data = i2c_get_clientdata(client);
>  	u8 page = rdev_get_id(rdev);
> +	int ret;
>  
> -	return pmbus_update_byte_data(client, page, PMBUS_OPERATION,
> -				      PB_OPERATION_CONTROL_ON,
> -				      enable ? PB_OPERATION_CONTROL_ON : 0);
> +	mutex_lock(&data->update_lock);
> +	ret = pmbus_update_byte_data(client, page, PMBUS_OPERATION,
> +				     PB_OPERATION_CONTROL_ON,
> +				     enable ? PB_OPERATION_CONTROL_ON : 0);
> +	mutex_unlock(&data->update_lock);
> +
> +	return ret;
>  }
>  
>  static int pmbus_regulator_enable(struct regulator_dev *rdev)