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Sender: Guenter Roeck <groeck7@gmail.com>
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Date:   Sat, 26 Feb 2022 15:47:41 -0800
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Subject: Re: [PATCH v1 1/1] drivers/hwmon/pmbus: Add mutex to regulator ops
Content-Language: en-US
To:     Zev Weiss <zweiss@equinix.com>,
        Marcello Sylvester Bauer <sylv@sylv.io>
Cc:     Jean Delvare <jdelvare@suse.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-hwmon@vger.kernel.org" <linux-hwmon@vger.kernel.org>,
        Patrick Rudolph <patrick.rudolph@9elements.com>
References: <b991506bcbf665f7af185945f70bf9d5cf04637c.1645804976.git.sylv@sylv.io>
 <20220226234220.GV5754@packtop>
From:   Guenter Roeck <linux@roeck-us.net>
In-Reply-To: <20220226234220.GV5754@packtop>
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On 2/26/22 15:42, Zev Weiss wrote:
> On Fri, Feb 25, 2022 at 08:06:09AM PST, Marcello Sylvester Bauer wrote:
>> From: Patrick Rudolph <patrick.rudolph@9elements.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@9elements.com>
>> Signed-off-by: Marcello Sylvester Bauer <sylv@sylv.io>
>> ---
>> 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)
>> -- 
>> 2.35.1
>>
>>
> 
> Looks like this doesn't cover pmbus_regulator_get_error_flags(), which
> was added recently -- perhaps rebase onto hwmon-next?
> 

This is a bug fix which needs to be applied to stable releases, or am I
missing something ?

Guenter