RE: [PATCH v3 3/3] eeprom: at24: enable runtime pm support

[Mohandass, Divagar]

Hi Sakari,

Thanks for your time.
My comments below.

---
^Divagar

>-----Original Message-----
>From: Sakari Ailus [mailto:sakari.ailus@xxxxxx]
>Sent: Wednesday, August 30, 2017 1:24 PM
>To: Mohandass, Divagar <divagar.mohandass@xxxxxxxxx>
>Cc: robh+dt@xxxxxxxxxx; mark.rutland@xxxxxxx; wsa@xxxxxxxxxxxxx;
>devicetree@xxxxxxxxxxxxxxx; linux-i2c@xxxxxxxxxxxxxxx; linux-
>kernel@xxxxxxxxxxxxxxx; Mani, Rajmohan <rajmohan.mani@xxxxxxxxx>
>Subject: Re: [PATCH v3 3/3] eeprom: at24: enable runtime pm support
>
>Hi Divagar,
>
>Thanks for the update. A few more comments below.
>
>On Wed, Aug 30, 2017 at 09:41:06AM +0530, Divagar Mohandass wrote:
>> Currently the device is kept in D0, there is an opportunity to save
>> power by enabling runtime pm.
>>
>> Device can be daisy chained from PMIC and we can't rely on I2C core
>> for auto resume/suspend. Driver will decide when to resume/suspend.
>>
>> Signed-off-by: Divagar Mohandass <divagar.mohandass@xxxxxxxxx>
>> ---
>>  drivers/misc/eeprom/at24.c | 39
>> +++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 39 insertions(+)
>>
>> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
>> index 2199c42..a670814 100644
>> --- a/drivers/misc/eeprom/at24.c
>> +++ b/drivers/misc/eeprom/at24.c
>> @@ -24,6 +24,7 @@
>>  #include <linux/i2c.h>
>>  #include <linux/nvmem-provider.h>
>>  #include <linux/platform_data/at24.h>
>> +#include <linux/pm_runtime.h>
>>
>>  /*
>>   * I2C EEPROMs from most vendors are inexpensive and mostly
>interchangeable.
>> @@ -501,11 +502,22 @@ static ssize_t at24_eeprom_write_i2c(struct
>> at24_data *at24, const char *buf,  static int at24_read(void *priv,
>> unsigned int off, void *val, size_t count)  {
>>  	struct at24_data *at24 = priv;
>> +	struct i2c_client *client;
>>  	char *buf = val;
>> +	int ret;
>>
>>  	if (unlikely(!count))
>>  		return count;
>>
>> +	client = at24_translate_offset(at24, &off);
>> +
>> +	ret = pm_runtime_get_sync(&client->dev);
>> +	if (ret < 0) {
>> +		pm_runtime_put_noidle(&client->dev);
>> +		pm_runtime_put(&client->dev);
>
>Two puts are too much here. How about dropping this one?

Ack
Will fix in next version.

>
>> +		return ret;
>> +	}
>> +
>>  	/*
>>  	 * Read data from chip, protecting against concurrent updates
>>  	 * from this host, but not from other I2C masters.
>
>If an error happens between the two chunks, you'll need pm_runtime_put(),
>too.
>

Ack

>> @@ -527,17 +539,30 @@ static int at24_read(void *priv, unsigned int
>> off, void *val, size_t count)
>>
>>  	mutex_unlock(&at24->lock);
>>
>> +	pm_runtime_put(&client->dev);
>> +
>>  	return 0;
>>  }
>>
>>  static int at24_write(void *priv, unsigned int off, void *val, size_t
>> count)  {
>>  	struct at24_data *at24 = priv;
>> +	struct i2c_client *client;
>>  	char *buf = val;
>> +	int ret;
>>
>>  	if (unlikely(!count))
>>  		return -EINVAL;
>>
>> +	client = at24_translate_offset(at24, &off);
>> +
>> +	ret = pm_runtime_get_sync(&client->dev);
>> +	if (ret < 0) {
>> +		pm_runtime_put_noidle(&client->dev);
>> +		pm_runtime_put(&client->dev);
>
>Same here.
>

Ack

>> +		return ret;
>> +	}
>> +
>>  	/*
>>  	 * Write data to chip, protecting against concurrent updates
>>  	 * from this host, but not from other I2C masters.
>
>Ditto.

Ack

>
>> @@ -559,6 +584,8 @@ static int at24_write(void *priv, unsigned int
>> off, void *val, size_t count)
>>
>>  	mutex_unlock(&at24->lock);
>>
>> +	pm_runtime_put(&client->dev);
>> +
>>  	return 0;
>>  }
>>
>> @@ -743,6 +770,15 @@ static int at24_probe(struct i2c_client *client,
>> const struct i2c_device_id *id)
>>
>>  	i2c_set_clientdata(client, at24);
>>
>> +	/* enable runtime pm */
>> +	pm_runtime_get_noresume(&client->dev);
>> +	err = pm_runtime_set_active(&client->dev);
>> +	if (err < 0)
>> +		goto err_clients;
>> +
>> +	pm_runtime_enable(&client->dev);
>> +	pm_runtime_put(&client->dev);
>> +
>
>You're just about to perform a read here. I believe you should move the last
>put after that.

At the end of at24_read we are performing a pm_runtime_put, still we need this change ?

>
>>  	/*
>>  	 * Perform a one-byte test read to verify that the
>>  	 * chip is functional.
>> @@ -810,6 +846,9 @@ static int at24_remove(struct i2c_client *client)
>>  	for (i = 1; i < at24->num_addresses; i++)
>>  		i2c_unregister_device(at24->client[i]);
>>
>> +	pm_runtime_disable(&client->dev);
>> +	pm_runtime_set_suspended(&client->dev);
>> +
>>  	return 0;
>>  }
>>
>
>--
>Regards,
>
>Sakari Ailus
>e-mail: sakari.ailus@xxxxxx