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

Started by"Mani, Rajmohan" <rajmohan.mani@intel.com>
First post2017-09-20 06:00 +0200
Last post2017-09-26 07:40 +0200
Articles 7 — 4 participants

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  RE: [PATCH v6 3/3] eeprom: at24: enable runtime pm support "Mani, Rajmohan" <rajmohan.mani@intel.com> - 2017-09-20 06:00 +0200
    Re: [PATCH v6 3/3] eeprom: at24: enable runtime pm support Tomasz Figa <tfiga@chromium.org> - 2017-09-20 06:00 +0200
      Re: [PATCH v6 3/3] eeprom: at24: enable runtime pm support "sakari.ailus@iki.fi" <sakari.ailus@iki.fi> - 2017-09-20 10:50 +0200
        Re: [PATCH v6 3/3] eeprom: at24: enable runtime pm support Tomasz Figa <tfiga@chromium.org> - 2017-09-20 11:00 +0200
          Re: [PATCH v6 3/3] eeprom: at24: enable runtime pm support "sakari.ailus@iki.fi" <sakari.ailus@iki.fi> - 2017-09-20 11:40 +0200
            RE: [PATCH v6 3/3] eeprom: at24: enable runtime pm support "Mohandass, Divagar" <divagar.mohandass@intel.com> - 2017-09-26 07:30 +0200
              Re: [PATCH v6 3/3] eeprom: at24: enable runtime pm support Tomasz Figa <tfiga@chromium.org> - 2017-09-26 07:40 +0200

#1735428 — RE: [PATCH v6 3/3] eeprom: at24: enable runtime pm support

From"Mani, Rajmohan" <rajmohan.mani@intel.com>
Date2017-09-20 06:00 +0200
SubjectRE: [PATCH v6 3/3] eeprom: at24: enable runtime pm support
Message-ID<urEl3-5X7-1@gated-at.bofh.it>
Adding Tomasz...

> -----Original Message-----
> From: Mohandass, Divagar
> Sent: Monday, September 04, 2017 3:29 AM
> To: robh+dt@kernel.org; mark.rutland@arm.com; wsa@the-dreams.de;
> sakari.ailus@iki.fi
> Cc: devicetree@vger.kernel.org; linux-i2c@vger.kernel.org; linux-
> kernel@vger.kernel.org; Mani, Rajmohan <rajmohan.mani@intel.com>;
> Mohandass, Divagar <divagar.mohandass@intel.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@intel.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

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#1735430

FromTomasz Figa <tfiga@chromium.org>
Date2017-09-20 06:00 +0200
Message-ID<urEl3-5X7-7@gated-at.bofh.it>
In reply to#1735428
Thanks Raj.

Let me post my comments inline.

On Wed, Sep 20, 2017 at 12:52 PM, Mani, Rajmohan
<rajmohan.mani@intel.com> wrote:
> Adding Tomasz...
>
>> -----Original Message-----
>> From: Mohandass, Divagar
>> Sent: Monday, September 04, 2017 3:29 AM
>> To: robh+dt@kernel.org; mark.rutland@arm.com; wsa@the-dreams.de;
>> sakari.ailus@iki.fi
>> Cc: devicetree@vger.kernel.org; linux-i2c@vger.kernel.org; linux-
>> kernel@vger.kernel.org; Mani, Rajmohan <rajmohan.mani@intel.com>;
>> Mohandass, Divagar <divagar.mohandass@intel.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@intel.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);

Do we need this get_noresume/set_active dance? I remember it was for
some reason needed for PCI devices, but I don't see why for I2C
anything else than just pm_runtime_enable() would be necessary.

Also, we enable runtime PM, but we don't provide any callbacks. If
there is no callback in any level of the hierarchy, NULL would be
returned in [3], making [2] return -ENOSYS and [1] fail. The behavior
depends on subsystem and whether the device is attached to a
pm_domain. In our particular case I'd guess the device would be in an
ACPI pm_domain and that would work, but the driver is generic and must
work in any cases.

[1] http://elixir.free-electrons.com/linux/v4.4.88/source/drivers/base/power/runtime.c#L738
[2] http://elixir.free-electrons.com/linux/v4.4.88/source/drivers/base/power/runtime.c#L364
[3] http://elixir.free-electrons.com/linux/v4.4.88/source/drivers/base/power/runtime.c#L19

Best regards,
Tomasz

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#1735647

From"sakari.ailus@iki.fi" <sakari.ailus@iki.fi>
Date2017-09-20 10:50 +0200
Message-ID<urIRI-Bk-29@gated-at.bofh.it>
In reply to#1735430
Hi Tomasz,

On Wed, Sep 20, 2017 at 12:56:09PM +0900, Tomasz Figa wrote:
> Thanks Raj.
> 
> Let me post my comments inline.
> 
> On Wed, Sep 20, 2017 at 12:52 PM, Mani, Rajmohan
> <rajmohan.mani@intel.com> wrote:
> > Adding Tomasz...
> >
> >> -----Original Message-----
> >> From: Mohandass, Divagar
> >> Sent: Monday, September 04, 2017 3:29 AM
> >> To: robh+dt@kernel.org; mark.rutland@arm.com; wsa@the-dreams.de;
> >> sakari.ailus@iki.fi
> >> Cc: devicetree@vger.kernel.org; linux-i2c@vger.kernel.org; linux-
> >> kernel@vger.kernel.org; Mani, Rajmohan <rajmohan.mani@intel.com>;
> >> Mohandass, Divagar <divagar.mohandass@intel.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@intel.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);
> 
> Do we need this get_noresume/set_active dance? I remember it was for
> some reason needed for PCI devices, but I don't see why for I2C
> anything else than just pm_runtime_enable() would be necessary.

You specifically do not need (all) this for PCI devices, but AFAIU for I²C
devices you do. The runtime PM status of a device is disabled by default
and the use count is zero, but on ACPI based systems the device is still
powered on.

> 
> Also, we enable runtime PM, but we don't provide any callbacks. If
> there is no callback in any level of the hierarchy, NULL would be
> returned in [3], making [2] return -ENOSYS and [1] fail. The behavior
> depends on subsystem and whether the device is attached to a
> pm_domain. In our particular case I'd guess the device would be in an
> ACPI pm_domain and that would work, but the driver is generic and must
> work in any cases.

Agreed.

Cc Mika, too.

-- 
Regards,

Sakari Ailus
e-mail: sakari.ailus@iki.fi

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#1735653

FromTomasz Figa <tfiga@chromium.org>
Date2017-09-20 11:00 +0200
Message-ID<urJ1o-Fm-7@gated-at.bofh.it>
In reply to#1735647
On Wed, Sep 20, 2017 at 5:45 PM, sakari.ailus@iki.fi
<sakari.ailus@iki.fi> wrote:
> Hi Tomasz,
>
> On Wed, Sep 20, 2017 at 12:56:09PM +0900, Tomasz Figa wrote:
>> Thanks Raj.
>>
>> Let me post my comments inline.
>>
>> On Wed, Sep 20, 2017 at 12:52 PM, Mani, Rajmohan
>> <rajmohan.mani@intel.com> wrote:
>> > Adding Tomasz...
>> >
>> >> -----Original Message-----
>> >> From: Mohandass, Divagar
>> >> Sent: Monday, September 04, 2017 3:29 AM
>> >> To: robh+dt@kernel.org; mark.rutland@arm.com; wsa@the-dreams.de;
>> >> sakari.ailus@iki.fi
>> >> Cc: devicetree@vger.kernel.org; linux-i2c@vger.kernel.org; linux-
>> >> kernel@vger.kernel.org; Mani, Rajmohan <rajmohan.mani@intel.com>;
>> >> Mohandass, Divagar <divagar.mohandass@intel.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@intel.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);
>>
>> Do we need this get_noresume/set_active dance? I remember it was for
>> some reason needed for PCI devices, but I don't see why for I2C
>> anything else than just pm_runtime_enable() would be necessary.
>
> You specifically do not need (all) this for PCI devices, but AFAIU for I涎
> devices you do. The runtime PM status of a device is disabled by default
> and the use count is zero, but on ACPI based systems the device is still
> powered on.

Okay, so _get_noresume() and _set_active() would do the thing for ACPI
indeed, but not sure about other platforms. Perhaps _enable(),
_get_sync() would be more general?

Bets regards,
Tomasz

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#1735667

From"sakari.ailus@iki.fi" <sakari.ailus@iki.fi>
Date2017-09-20 11:40 +0200
Message-ID<urJE5-19d-7@gated-at.bofh.it>
In reply to#1735653
Hi Tomasz,

On Wed, Sep 20, 2017 at 05:59:18PM +0900, Tomasz Figa wrote:
> On Wed, Sep 20, 2017 at 5:45 PM, sakari.ailus@iki.fi
> <sakari.ailus@iki.fi> wrote:
> > Hi Tomasz,
> >
> > On Wed, Sep 20, 2017 at 12:56:09PM +0900, Tomasz Figa wrote:
> >> Thanks Raj.
> >>
> >> Let me post my comments inline.
> >>
> >> On Wed, Sep 20, 2017 at 12:52 PM, Mani, Rajmohan
> >> <rajmohan.mani@intel.com> wrote:
> >> > Adding Tomasz...
> >> >
> >> >> -----Original Message-----
> >> >> From: Mohandass, Divagar
> >> >> Sent: Monday, September 04, 2017 3:29 AM
> >> >> To: robh+dt@kernel.org; mark.rutland@arm.com; wsa@the-dreams.de;
> >> >> sakari.ailus@iki.fi
> >> >> Cc: devicetree@vger.kernel.org; linux-i2c@vger.kernel.org; linux-
> >> >> kernel@vger.kernel.org; Mani, Rajmohan <rajmohan.mani@intel.com>;
> >> >> Mohandass, Divagar <divagar.mohandass@intel.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@intel.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);
> >>
> >> Do we need this get_noresume/set_active dance? I remember it was for
> >> some reason needed for PCI devices, but I don't see why for I2C
> >> anything else than just pm_runtime_enable() would be necessary.
> >
> > You specifically do not need (all) this for PCI devices, but AFAIU for I涎
> > devices you do. The runtime PM status of a device is disabled by default
> > and the use count is zero, but on ACPI based systems the device is still
> > powered on.
> 
> Okay, so _get_noresume() and _set_active() would do the thing for ACPI
> indeed, but not sure about other platforms. Perhaps _enable(),
> _get_sync() would be more general?

What I ended up doing in e.g. the smiapp driver was to explicitly power the
device on first and then enable runtime PM. (See
drivers/media/i2c/smiapp/smiapp-core.c .) This approach works even if
CONFIG_PM is disabled, both on DT and ACPI.

-- 
Regards,

Sakari Ailus
e-mail: sakari.ailus@iki.fi

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#1739519

From"Mohandass, Divagar" <divagar.mohandass@intel.com>
Date2017-09-26 07:30 +0200
Message-ID<utQBr-k1-3@gated-at.bofh.it>
In reply to#1735667
Hi Sakari & Tomas,

Are you ok with the current revision, let me know if any changes are needed.

---
^Divagar

>-----Original Message-----
>From: sakari.ailus@iki.fi [mailto:sakari.ailus@iki.fi]
>Sent: Wednesday, September 20, 2017 3:02 PM
>To: Tomasz Figa <tfiga@chromium.org>
>Cc: Mani, Rajmohan <rajmohan.mani@intel.com>; Mohandass, Divagar
><divagar.mohandass@intel.com>; robh+dt@kernel.org;
>mark.rutland@arm.com; wsa@the-dreams.de; devicetree@vger.kernel.org;
>linux-i2c@vger.kernel.org; linux-kernel@vger.kernel.org;
>mika.westerberg@linux.intel.com
>Subject: Re: [PATCH v6 3/3] eeprom: at24: enable runtime pm support
>
>Hi Tomasz,
>
>On Wed, Sep 20, 2017 at 05:59:18PM +0900, Tomasz Figa wrote:
>> On Wed, Sep 20, 2017 at 5:45 PM, sakari.ailus@iki.fi
>> <sakari.ailus@iki.fi> wrote:
>> > Hi Tomasz,
>> >
>> > On Wed, Sep 20, 2017 at 12:56:09PM +0900, Tomasz Figa wrote:
>> >> Thanks Raj.
>> >>
>> >> Let me post my comments inline.
>> >>
>> >> On Wed, Sep 20, 2017 at 12:52 PM, Mani, Rajmohan
>> >> <rajmohan.mani@intel.com> wrote:
>> >> > Adding Tomasz...
>> >> >
>> >> >> -----Original Message-----
>> >> >> From: Mohandass, Divagar
>> >> >> Sent: Monday, September 04, 2017 3:29 AM
>> >> >> To: robh+dt@kernel.org; mark.rutland@arm.com; wsa@the-
>dreams.de;
>> >> >> sakari.ailus@iki.fi
>> >> >> Cc: devicetree@vger.kernel.org; linux-i2c@vger.kernel.org;
>> >> >> linux- kernel@vger.kernel.org; Mani, Rajmohan
>> >> >> <rajmohan.mani@intel.com>; Mohandass, Divagar
>> >> >> <divagar.mohandass@intel.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@intel.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);
>> >>
>> >> Do we need this get_noresume/set_active dance? I remember it was
>> >> for some reason needed for PCI devices, but I don't see why for I2C
>> >> anything else than just pm_runtime_enable() would be necessary.
>> >
>> > You specifically do not need (all) this for PCI devices, but AFAIU
>> > for I涎
>> > devices you do. The runtime PM status of a device is disabled by
>> > default and the use count is zero, but on ACPI based systems the
>> > device is still powered on.
>>
>> Okay, so _get_noresume() and _set_active() would do the thing for ACPI
>> indeed, but not sure about other platforms. Perhaps _enable(),
>> _get_sync() would be more general?
>
>What I ended up doing in e.g. the smiapp driver was to explicitly power the
>device on first and then enable runtime PM. (See
>drivers/media/i2c/smiapp/smiapp-core.c .) This approach works even if
>CONFIG_PM is disabled, both on DT and ACPI.
>
>--
>Regards,
>
>Sakari Ailus
>e-mail: sakari.ailus@iki.fi

[toc] | [prev] | [next] | [standalone]

#1739520

FromTomasz Figa <tfiga@chromium.org>
Date2017-09-26 07:40 +0200
Message-ID<utQL7-nC-1@gated-at.bofh.it>
In reply to#1739519
[+Rafael, Ulf]

On Tue, Sep 26, 2017 at 2:29 PM, Mohandass, Divagar
<divagar.mohandass@intel.com> wrote:
> Hi Sakari & Tomas,
>
> Are you ok with the current revision, let me know if any changes are needed.

Nope, my concerns have not been addressed, but we need someone from
the PM world to clarify how we should do this to work on all
platforms.

Best regards,
Tomasz

P.S. Please avoid top-posting on mailing lists, it is considered bad manner.

>
> ---
> ^Divagar
>
>>-----Original Message-----
>>From: sakari.ailus@iki.fi [mailto:sakari.ailus@iki.fi]
>>Sent: Wednesday, September 20, 2017 3:02 PM
>>To: Tomasz Figa <tfiga@chromium.org>
>>Cc: Mani, Rajmohan <rajmohan.mani@intel.com>; Mohandass, Divagar
>><divagar.mohandass@intel.com>; robh+dt@kernel.org;
>>mark.rutland@arm.com; wsa@the-dreams.de; devicetree@vger.kernel.org;
>>linux-i2c@vger.kernel.org; linux-kernel@vger.kernel.org;
>>mika.westerberg@linux.intel.com
>>Subject: Re: [PATCH v6 3/3] eeprom: at24: enable runtime pm support
>>
>>Hi Tomasz,
>>
>>On Wed, Sep 20, 2017 at 05:59:18PM +0900, Tomasz Figa wrote:
>>> On Wed, Sep 20, 2017 at 5:45 PM, sakari.ailus@iki.fi
>>> <sakari.ailus@iki.fi> wrote:
>>> > Hi Tomasz,
>>> >
>>> > On Wed, Sep 20, 2017 at 12:56:09PM +0900, Tomasz Figa wrote:
>>> >> Thanks Raj.
>>> >>
>>> >> Let me post my comments inline.
>>> >>
>>> >> On Wed, Sep 20, 2017 at 12:52 PM, Mani, Rajmohan
>>> >> <rajmohan.mani@intel.com> wrote:
>>> >> > Adding Tomasz...
>>> >> >
>>> >> >> -----Original Message-----
>>> >> >> From: Mohandass, Divagar
>>> >> >> Sent: Monday, September 04, 2017 3:29 AM
>>> >> >> To: robh+dt@kernel.org; mark.rutland@arm.com; wsa@the-
>>dreams.de;
>>> >> >> sakari.ailus@iki.fi
>>> >> >> Cc: devicetree@vger.kernel.org; linux-i2c@vger.kernel.org;
>>> >> >> linux- kernel@vger.kernel.org; Mani, Rajmohan
>>> >> >> <rajmohan.mani@intel.com>; Mohandass, Divagar
>>> >> >> <divagar.mohandass@intel.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@intel.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);
>>> >>
>>> >> Do we need this get_noresume/set_active dance? I remember it was
>>> >> for some reason needed for PCI devices, but I don't see why for I2C
>>> >> anything else than just pm_runtime_enable() would be necessary.
>>> >
>>> > You specifically do not need (all) this for PCI devices, but AFAIU
>>> > for I涎
>>> > devices you do. The runtime PM status of a device is disabled by
>>> > default and the use count is zero, but on ACPI based systems the
>>> > device is still powered on.
>>>
>>> Okay, so _get_noresume() and _set_active() would do the thing for ACPI
>>> indeed, but not sure about other platforms. Perhaps _enable(),
>>> _get_sync() would be more general?
>>
>>What I ended up doing in e.g. the smiapp driver was to explicitly power the
>>device on first and then enable runtime PM. (See
>>drivers/media/i2c/smiapp/smiapp-core.c .) This approach works even if
>>CONFIG_PM is disabled, both on DT and ACPI.
>>
>>--
>>Regards,
>>
>>Sakari Ailus
>>e-mail: sakari.ailus@iki.fi

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