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SubjectRe: [PATCH v4 5/6] at24: Support probing while off
wt., 21 sty 2020 o 14:41 Sakari Ailus <sakari.ailus@linux.intel.com> napisał(a):
>
> 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@linux.intel.com>
> ---
> drivers/misc/eeprom/at24.c | 31 +++++++++++++++++++++----------
> 1 file changed, 21 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index 0681d5fdd538a..5fc1162b67618 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -564,6 +564,7 @@ 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;
> @@ -701,19 +702,24 @@ static int at24_probe(struct i2c_client *client)
>
> i2c_set_clientdata(client, at24);
>
> - /* enable runtime pm */
> - pm_runtime_set_active(dev);
> + low_power = acpi_dev_state_low_power(&client->dev);
> + if (!low_power)
> + 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);
> - pm_runtime_idle(dev);
> - if (err) {
> - pm_runtime_disable(dev);
> - return -ENODEV;
> + if (!low_power) {
> + err = at24_read(at24, 0, &test_byte, 1);
> + pm_runtime_idle(dev);
> + if (err) {
> + pm_runtime_disable(dev);
> + return -ENODEV;
> + }
> }
>
> if (writable)
> @@ -728,8 +734,12 @@ static int at24_probe(struct i2c_client *client)
>
> static int at24_remove(struct i2c_client *client)
> {
> + bool low_power;
> +
> pm_runtime_disable(&client->dev);
> - pm_runtime_set_suspended(&client->dev);
> + low_power = acpi_dev_state_low_power(&client->dev);

This is inconsistent. You define the low_power field in the context
structure (BTW the name low_power is a bit vague here - without
looking at its assignment it would make me think it's about something
battery-related, how about 'off_at_probe'?) and instead of reusing
this field here, you call acpi_dev_state_low_power() again. Either
don't store the context for the life-time of the device if not
necessary or don't call acpi_dev_state_low_power() at remove, although
the commit message doesn't describe whether the latter is done on
purpose.

Bartosz

> + if (!low_power)
> + pm_runtime_set_suspended(&client->dev);
>
> return 0;
> }
> @@ -743,6 +753,7 @@ static struct i2c_driver at24_driver = {
> .probe_new = at24_probe,
> .remove = at24_remove,
> .id_table = at24_ids,
> + .probe_low_power = true,
> };
>
> static int __init at24_init(void)
> --
> 2.20.1
>

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