Re: [PATCH v6 3/3] eeprom: at24: enable runtime pm support
Hi Tomasz, On Wed, Sep 20, 2017 at 12:32:22PM +0300, sakari.ai...@iki.fi wrote: > > >> >> @@ -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. pm_runtime_get_noresume() + pm_runtime_put() can be replaced by a single pm_runtime_idle() call (where pm_runtime_put() was). pm_runtime_enable() is required to enable runtime PM for a device. pm_runtime_allow() may be omitted but then to make the runtime PM framework to make the power state transitions this needs to be configured from the user space --- which I don't think is intended. Cc linux-pm, too. -- Regards, Sakari Ailus e-mail: sakari.ai...@iki.fi
Re: [PATCH v6 3/3] eeprom: at24: enable runtime pm support
On Wed, Sep 20, 2017 at 11:45:20AM +0300, sakari.ai...@iki.fi wrote: > > >> @@ -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. I looked at the code and what actually happens here is the runtime_suspend and runtime_resume callbacks aren't set is that the first pm_runtime_put() call itself succeeds because checking the the runtime_suspend callback will be done in the work queue function. This leaves the device in RPM_ACTIVE state, which I don't think is a problem since the driver did not have explicit functions to control the device power state. Further pm_runtime_put() and pm_runtime_get() calls will succeed because the device is in RPM_ACTIVE state. So I see no reason to set the callbacks if they would not actually control regulators, clocks or GPIOs required by the device. Cc linux-pm. -- Kind regards, Sakari Ailus e-mail: sakari.ai...@iki.fi
Re: [PATCH v6 3/3] eeprom: at24: enable runtime pm support
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
> wrote:
> > Adding Tomasz...
> >
> >> -Original Message-
> >> From: Mohandass, Divagar
> >> Sent: Monday, September 04, 2017 3:29 AM
> >> To: robh...@kernel.org; mark.rutl...@arm.com; w...@the-dreams.de;
> >> sakari.ai...@iki.fi
> >> Cc: devicet...@vger.kernel.org; linux-...@vger.kernel.org; linux-
> >> ker...@vger.kernel.org; Mani, Rajmohan ;
> >> Mohandass, Divagar
> >> 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
> >> ---
> >> 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
> >> #include
> >> #include
> >> +#include
> >>
> >> /*
> >> * 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);
> >> +
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.ai...@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
> >> wrote:
> >> > Adding Tomasz...
> >> >
> >> >> -Original Message-
> >> >> From: Mohandass, Divagar
> >> >> Sent: Monday, September 04, 2017 3:29 AM
> >> >> To: robh...@kernel.org; mark.rutl...@arm.com; w...@the-dreams.de;
> >> >> sakari.ai...@iki.fi
> >> >> Cc: devicet...@vger.kernel.org; linux-...@vger.kernel.org; linux-
> >> >> ker...@vger.kernel.org; Mani, Rajmohan ;
> >> >> Mohandass, Divagar
> >> >> 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
> >> >> ---
> >> >> 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
> >> >> #include
> >> >> #include
> >> >> +#include
> >> >>
> >> >> /*
> >> >> * 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
