Hi Mika
Thanks for your review!
On Mon, 14 Nov 2022 at 11:33, Mika Westerberg
<mika.westerberg@xxxxxxxxxxxxxxx> wrote:
>
> Hi,
>
> On Sat, Nov 12, 2022 at 09:24:14PM +0100, Wolfram Sang wrote:
> > On Thu, Nov 10, 2022 at 05:20:39PM +0100, Ricardo Ribalda wrote:
> > > A driver that supports I2C_DRV_ACPI_WAIVE_D0_PROBE is not expected to
> > > power off a device that it has not powered on previously.
> > >
> > > For devices operating in "full_power" mode, the first call to
> > > `i2c_acpi_waive_d0_probe` will return 0, which means that the device
> > > will be turned on with `dev_pm_domain_attach`.
> > >
> > > If probe fails or the device is removed the second call to
> > > `i2c_acpi_waive_d0_probe` will return 1, which means that the device
> > > will not be turned off. This is, it will be left in a different power
> > > state. Lets fix it.
> > >
> > > Reviewed-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> > > Cc: stable@xxxxxxxxxxxxxxx
> > > Fixes: b18c1ad685d9 ("i2c: Allow an ACPI driver to manage the device's power state during probe")
> > > Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> >
> > Adding I2C ACPI maintainer to CC. Mika, could you please help
> > reviewing?
>
> Sure.
>
> > > diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> > > index b4edf10e8fd0..6f4974c76404 100644
> > > --- a/drivers/i2c/i2c-core-base.c
> > > +++ b/drivers/i2c/i2c-core-base.c
> > > @@ -467,6 +467,7 @@ static int i2c_device_probe(struct device *dev)
> > > {
> > > struct i2c_client *client = i2c_verify_client(dev);
> > > struct i2c_driver *driver;
> > > + bool do_power_on;
> > > int status;
> > >
> > > if (!client)
> > > @@ -545,8 +546,8 @@ static int i2c_device_probe(struct device *dev)
> > > if (status < 0)
> > > goto err_clear_wakeup_irq;
> > >
> > > - status = dev_pm_domain_attach(&client->dev,
> > > - !i2c_acpi_waive_d0_probe(dev));
> > > + do_power_on = !i2c_acpi_waive_d0_probe(dev);
> > > + status = dev_pm_domain_attach(&client->dev, do_power_on);
>
> I think this is fine as the driver says it is OK to see the device in
> whatever power state (I assume this is what the
> i2c_acpi_waive_d0_probe() is supposed to be doing but there is no
> kernel-doc, though).
>
> > > if (status)
> > > goto err_clear_wakeup_irq;
> > >
> > > @@ -580,12 +581,14 @@ static int i2c_device_probe(struct device *dev)
> > > if (status)
> > > goto err_release_driver_resources;
> > >
> > > + client->power_off_on_remove = do_power_on;
> > > +
> > > return 0;
> > >
> > > err_release_driver_resources:
> > > devres_release_group(&client->dev, client->devres_group_id);
> > > err_detach_pm_domain:
> > > - dev_pm_domain_detach(&client->dev, !i2c_acpi_waive_d0_probe(dev));
> > > + dev_pm_domain_detach(&client->dev, do_power_on);
> > > err_clear_wakeup_irq:
> > > dev_pm_clear_wake_irq(&client->dev);
> > > device_init_wakeup(&client->dev, false);
> > > @@ -610,7 +613,7 @@ static void i2c_device_remove(struct device *dev)
> > >
> > > devres_release_group(&client->dev, client->devres_group_id);
> > >
> > > - dev_pm_domain_detach(&client->dev, !i2c_acpi_waive_d0_probe(dev));
> > > + dev_pm_domain_detach(&client->dev, client->power_off_on_remove);
>
> However, on the remove path I think we should not call
> i2c_acpi_waive_d0_probe() at all as that has nothing to do with remove
> (it is for whether the driver accepts any power state on probe AFAICT)
> so this should stil be "true" here. Unless I'm missing something.
I guess the problem is that we would be undoing something (power-off),
that we did not do.
Sakari, can you think of a use-case where this can break something? If
not I can send a v6.
Regards!
>
> > >
> > > 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 f7c49bbdb8a1..eba83bc5459e 100644
> > > --- a/include/linux/i2c.h
> > > +++ b/include/linux/i2c.h
> > > @@ -326,6 +326,8 @@ struct i2c_driver {
> > > * calls it to pass on slave events to the slave driver.
> > > * @devres_group_id: id of the devres group that will be created for resources
> > > * acquired when probing this device.
> > > + * @power_off_on_remove: Record if we have turned on the device before probing
> > > + * so we can turn off the device at removal.
> > > *
> > > * An i2c_client identifies a single device (i.e. chip) connected to an
> > > * i2c bus. The behaviour exposed to Linux is defined by the driver
> > > @@ -355,6 +357,8 @@ struct i2c_client {
> > > i2c_slave_cb_t slave_cb; /* callback for slave mode */
> > > #endif
> > > void *devres_group_id; /* ID of probe devres group */
> > > + bool power_off_on_remove; /* if device needs to be turned */
> > > + /* off by framework at removal */
> > > };
> > > #define to_i2c_client(d) container_of(d, struct i2c_client, dev)
> > >
> > >
> > > --
> > > b4 0.11.0-dev-d93f8
>
>
--
Ricardo Ribalda
