Re: [PATCH v4 1/6] i2c: Allow driver to manage the device's power state during probe

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Bartosz,

On Wed, Jan 29, 2020 at 02:54:20PM +0100, Bartosz Golaszewski wrote:
> wt., 21 sty 2020 o 14:41 Sakari Ailus <sakari.ailus@linux.intel.com> napisał(a):
> >
> > Enable drivers to tell ACPI that there's no need to power on a device for
> > probe. Drivers should still perform this by themselves if there's a need
> > to. In some cases powering on the device during probe is undesirable, and
> > this change enables a driver to choose what fits best for it.
> >
> > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > ---
> >  drivers/i2c/i2c-core-base.c | 15 ++++++++++++---
> >  include/linux/i2c.h         |  3 +++
> >  2 files changed, 15 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> > index 9f8dcd3f83850..7bf1699c9044d 100644
> > --- a/drivers/i2c/i2c-core-base.c
> > +++ b/drivers/i2c/i2c-core-base.c
> > @@ -303,6 +303,14 @@ static int i2c_smbus_host_notify_to_irq(const struct i2c_client *client)
> >         return irq > 0 ? irq : -ENXIO;
> >  }
> >
> > +static bool probe_low_power(struct device *dev)
> > +{
> > +       struct i2c_driver *driver = to_i2c_driver(dev->driver);
> > +
> > +       return driver->probe_low_power &&
> > +               device_property_present(dev, "probe-low-power");
> > +}
> > +
> >  static int i2c_device_probe(struct device *dev)
> >  {
> >         struct i2c_client       *client = i2c_verify_client(dev);
> > @@ -375,7 +383,8 @@ static int i2c_device_probe(struct device *dev)
> >         if (status < 0)
> >                 goto err_clear_wakeup_irq;
> >
> > -       status = dev_pm_domain_attach(&client->dev, true);
> > +       status = dev_pm_domain_attach(&client->dev,
> > +                                     !probe_low_power(&client->dev));
> >         if (status)
> >                 goto err_clear_wakeup_irq;
> >
> > @@ -397,7 +406,7 @@ static int i2c_device_probe(struct device *dev)
> >         return 0;
> >
> >  err_detach_pm_domain:
> > -       dev_pm_domain_detach(&client->dev, true);
> > +       dev_pm_domain_detach(&client->dev, !probe_low_power(&client->dev));
> >  err_clear_wakeup_irq:
> >         dev_pm_clear_wake_irq(&client->dev);
> >         device_init_wakeup(&client->dev, false);
> > @@ -419,7 +428,7 @@ static int i2c_device_remove(struct device *dev)
> >                 status = driver->remove(client);
> >         }
> >
> > -       dev_pm_domain_detach(&client->dev, true);
> > +       dev_pm_domain_detach(&client->dev, !probe_low_power(&client->dev));
> >
> >         dev_pm_clear_wake_irq(&client->dev);
> >         device_init_wakeup(&client->dev, false);
> > diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> > index 582ef05ec07ed..6d0d6af393c56 100644
> > --- a/include/linux/i2c.h
> > +++ b/include/linux/i2c.h
> > @@ -229,6 +229,8 @@ enum i2c_alert_protocol {
> >   * @address_list: The I2C addresses to probe (for detect)
> >   * @clients: List of detected clients we created (for i2c-core use only)
> >   * @disable_i2c_core_irq_mapping: Tell the i2c-core to not do irq-mapping
> > + * @probe_low_power: Let the driver manage the device's power state
> > + *                  during probe and remove.
> >   *
> >   * The driver.owner field should be set to the module owner of this driver.
> >   * The driver.name field should be set to the name of this driver.
> > @@ -289,6 +291,7 @@ struct i2c_driver {
> >         struct list_head clients;
> >
> >         bool disable_i2c_core_irq_mapping;
> > +       bool probe_low_power;
> 
> I don't see any users of disable_i2c_core_irq_mapping in current
> mainline. Maybe instead of adding another 1-byte boolean for every
> such property, let's just use the fact that this struct will have at
> least an alignment of 32-bits anyway and merge the two into an int
> field called 'flags' so that we can extend it in the future if needed?
> 
> The name 'probe_low_power' is misleading to me too. It makes me think
> it's the default state for some reason. It should be something like
> 'allow_low_power_probe'.

Ah, got around reading this one after sending the previous mail.

Sounds reasonable. I'll address both in v5.

-- 
Kind regards,

Sakari Ailus