linux-kernel - RE: [PATCH v6 3/3] eeprom: at24: enable runtime pm support

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Date:   Wed, 20 Sep 2017 03:52:53 +0000
From:   "Mani, Rajmohan" <rajmohan.mani@...el.com>
To:     "Mohandass, Divagar" <divagar.mohandass@...el.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "wsa@...-dreams.de" <wsa@...-dreams.de>,
        "sakari.ailus@....fi" <sakari.ailus@....fi>
CC:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tfiga@...omium.org" <tfiga@...omium.org>
Subject: RE: [PATCH v6 3/3] eeprom: at24: enable runtime pm support

Adding Tomasz...

> -----Original Message-----
> From: Mohandass, Divagar
> Sent: Monday, September 04, 2017 3:29 AM
> To: robh+dt@...nel.org; mark.rutland@....com; wsa@...-dreams.de;
> sakari.ailus@....fi
> Cc: devicetree@...r.kernel.org; linux-i2c@...r.kernel.org; linux-
> kernel@...r.kernel.org; Mani, Rajmohan <rajmohan.mani@...el.com>;
> Mohandass, Divagar <divagar.mohandass@...el.com>
> Subject: [PATCH v6 3/3] eeprom: at24: enable runtime pm support
> 
> 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@...el.com>
> ---
>  drivers/misc/eeprom/at24.c | 38
> ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c index
> 2199c42..d718a7a 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 +502,21 @@ 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);
> +		return ret;
> +	}
> +
>  	/*
>  	 * Read data from chip, protecting against concurrent updates
>  	 * from this host, but not from other I2C masters.
> @@ -518,6 +529,7 @@ static int at24_read(void *priv, unsigned int off, void
> *val, size_t count)
>  		status = at24->read_func(at24, buf, off, count);
>  		if (status < 0) {
>  			mutex_unlock(&at24->lock);
> +			pm_runtime_put(&client->dev);
>  			return status;
>  		}
>  		buf += status;
> @@ -527,17 +539,29 @@ 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);
> +		return ret;
> +	}
> +
>  	/*
>  	 * Write data to chip, protecting against concurrent updates
>  	 * from this host, but not from other I2C masters.
> @@ -550,6 +574,7 @@ static int at24_write(void *priv, unsigned int off, void
> *val, size_t count)
>  		status = at24->write_func(at24, buf, off, count);
>  		if (status < 0) {
>  			mutex_unlock(&at24->lock);
> +			pm_runtime_put(&client->dev);
>  			return status;
>  		}
>  		buf += status;
> @@ -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;
>  }
> 
> @@ -743,11 +770,17 @@ 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);
> +	pm_runtime_set_active(&client->dev);
> +	pm_runtime_enable(&client->dev);
> +
>  	/*
>  	 * Perform a one-byte test read to verify that the
>  	 * chip is functional.
>  	 */
>  	err = at24_read(at24, 0, &test_byte, 1);
> +	pm_runtime_put(&client->dev);
>  	if (err) {
>  		err = -ENODEV;
>  		goto err_clients;
> @@ -795,6 +828,8 @@ static int at24_probe(struct i2c_client *client, const
> struct i2c_device_id *id)
>  		if (at24->client[i])
>  			i2c_unregister_device(at24->client[i]);
> 
> +	pm_runtime_disable(&client->dev);
> +
>  	return err;
>  }
> 
> @@ -810,6 +845,9 @@ 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;
>  }
> 
> --
> 1.9.1