[v4,5/6] at24: Support probing while off
diff mbox series

Message ID 20200121134157.20396-6-sakari.ailus@linux.intel.com
State Changes Requested
Headers show
Series
  • Support running driver's probe for a device powered off
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Commit Message

Sakari Ailus Jan. 21, 2020, 1:41 p.m. UTC
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(-)

Comments

Bartosz Golaszewski Jan. 29, 2020, 1:36 p.m. UTC | #1
wt., 21 sty 2020 o 14:41 Sakari Ailus <sakari.ailus@linux.intel.com> napisaƂ(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
>

Patch
diff mbox series

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);
+	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)