Date:   Mon, 14 Nov 2022 11:51:24 +0100
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Wolfram Sang <wsa@...nel.org>, Tomasz Figa <tfiga@...omium.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Hidenori Kobayashi <hidenorik@...gle.com>,
        stable@...r.kernel.org, linux-i2c@...r.kernel.org,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/1] i2c: Restore initial power state when we are done.

Hi Mika

Thanks for your review!

On Mon, 14 Nov 2022 at 11:33, Mika Westerberg
<mika.westerberg@...ux.intel.com> 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@...ux.intel.com>
> > > Cc: stable@...r.kernel.org
> > > Fixes: b18c1ad685d9 ("i2c: Allow an ACPI driver to manage the device's power state during probe")
> > > Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> >
> > 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

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