linux-kernel - Re: [PATCH v8 6/6] at24: Support probing while off

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Date:   Wed, 9 Sep 2020 11:35:45 +0200
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     linux-i2c <linux-i2c@...r.kernel.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rajmohan Mani <rajmohan.mani@...el.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Bingbu Cao <bingbu.cao@...el.com>,
        Chiranjeevi Rapolu <chiranjeevi.rapolu@...el.com>,
        Hyungwoo Yang <hyungwoo.yang@...el.com>,
        linux-media <linux-media@...r.kernel.org>
Subject: Re: [PATCH v8 6/6] at24: Support probing while off

On Thu, Sep 3, 2020 at 10:15 AM Sakari Ailus
<sakari.ailus@...ux.intel.com> wrote:
>
> In certain use cases (where the chip is part of a camera module, and the
> camera module is wired together with a camera privacy LED), powering on
> the device during probe is undesirable. Add support for the at24 to
> execute probe while being powered off. For this to happen, a hint in form
> of a device property is required from the firmware.
>
> Signed-off-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> ---
>  drivers/misc/eeprom/at24.c | 43 +++++++++++++++++++++++---------------
>  1 file changed, 26 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index 8f5de5f10bbea..2d24e33788d7d 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -595,6 +595,7 @@ static int at24_probe(struct i2c_client *client)
>         bool i2c_fn_i2c, i2c_fn_block;
>         unsigned int i, num_addresses;
>         struct at24_data *at24;
> +       bool low_power;
>         struct regmap *regmap;
>         bool writable;
>         u8 test_byte;
> @@ -733,25 +734,30 @@ static int at24_probe(struct i2c_client *client)
>
>         i2c_set_clientdata(client, at24);
>
> -       err = regulator_enable(at24->vcc_reg);
> -       if (err) {
> -               dev_err(dev, "Failed to enable vcc regulator\n");
> -               return err;
> -       }
> +       low_power = acpi_dev_state_low_power(&client->dev);
> +       if (!low_power) {
> +               err = regulator_enable(at24->vcc_reg);
> +               if (err) {
> +                       dev_err(dev, "Failed to enable vcc regulator\n");
> +                       return err;
> +               }
>
> -       /* enable runtime pm */
> -       pm_runtime_set_active(dev);
> +               pm_runtime_set_active(dev);
> +       }
>         pm_runtime_enable(dev);
>
>         /*
> -        * Perform a one-byte test read to verify that the
> -        * chip is functional.
> +        * Perform a one-byte test read to verify that the chip is functional,
> +        * unless powering on the device is to be avoided during probe (i.e.
> +        * it's powered off right now).
>          */
> -       err = at24_read(at24, 0, &test_byte, 1);
> -       if (err) {
> -               pm_runtime_disable(dev);
> -               regulator_disable(at24->vcc_reg);
> -               return -ENODEV;
> +       if (!low_power) {
> +               err = at24_read(at24, 0, &test_byte, 1);
> +               if (err) {
> +                       pm_runtime_disable(dev);
> +                       regulator_disable(at24->vcc_reg);
> +                       return -ENODEV;
> +               }
>         }
>
>         pm_runtime_idle(dev);
> @@ -771,9 +777,11 @@ static int at24_remove(struct i2c_client *client)
>         struct at24_data *at24 = i2c_get_clientdata(client);
>
>         pm_runtime_disable(&client->dev);
> -       if (!pm_runtime_status_suspended(&client->dev))
> -               regulator_disable(at24->vcc_reg);
> -       pm_runtime_set_suspended(&client->dev);
> +       if (!acpi_dev_state_low_power(&client->dev)) {
> +               if (!pm_runtime_status_suspended(&client->dev))
> +                       regulator_disable(at24->vcc_reg);
> +               pm_runtime_set_suspended(&client->dev);
> +       }
>
>         return 0;
>  }
> @@ -810,6 +818,7 @@ static struct i2c_driver at24_driver = {
>         .probe_new = at24_probe,
>         .remove = at24_remove,
>         .id_table = at24_ids,
> +       .flags = I2C_DRV_FL_ALLOW_LOW_POWER_PROBE,
>  };
>
>  static int __init at24_init(void)
> --
> 2.20.1
>

This currently conflicts with the fix I queued for at24 for v5.9.
Which tree is going to take this series?

Bartosz