[PATCH v5 5/6] at24: Support probing while off

Sakari Ailus
2020-08-10T14:25:29Z

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 | 40 ++++++++++++++++++++++++--------------
1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 2591c21b2b5d8..e597a8861e817 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -561,6 +561,7 @@ 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;
@@ -698,25 +699,30 @@ 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);
@@ -734,11 +740,14 @@ static int at24_probe(struct i2c_client *client)
static int at24_remove(struct i2c_client *client)
{
struct at24_data *at24 = i2c_get_clientdata(client);
+ bool low_power;

pm_runtime_disable(&client->dev);
if (!pm_runtime_status_suspended(&client->dev))
regulator_disable(at24->vcc_reg);
- 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;
}
@@ -775,6 +784,7 @@ 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