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

[Sakari Ailus]

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.ai...@linux.intel.com>
---
 drivers/misc/eeprom/at24.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 63aa541c96088..b9dbe5b6a97be 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -579,6 +579,7 @@ 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 powered_off;
        struct regmap *regmap;
        size_t at24_size;
        bool writable;
@@ -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);
+       powered_off = acpi_dev_powered_off_for_probe(&client->dev);
+       if (!powered_off)
+               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) {
-               err = -ENODEV;
-               goto err_clients;
+       if (!powered_off) {
+               err = at24_read(at24, 0, &test_byte, 1);
+               pm_runtime_idle(dev);
+               if (err) {
+                       err = -ENODEV;
+                       goto err_clients;
+               }
        }
 
        nvmem_config.name = dev_name(dev);
@@ -752,12 +758,15 @@ static int at24_probe(struct i2c_client *client)
 static int at24_remove(struct i2c_client *client)
 {
        struct at24_data *at24;
+       bool powered_off;
 
        at24 = i2c_get_clientdata(client);
 
        at24_remove_dummy_clients(at24);
        pm_runtime_disable(&client->dev);
-       pm_runtime_set_suspended(&client->dev);
+       powered_off = acpi_dev_powered_off_for_probe(&client->dev);
+       if (!powered_off)
+               pm_runtime_set_suspended(&client->dev);
 
        return 0;
 }
@@ -765,6 +774,7 @@ static int at24_remove(struct i2c_client *client)
 static struct i2c_driver at24_driver = {
        .driver = {
                .name = "at24",
+               .probe_powered_off = true,
                .of_match_table = at24_of_match,
                .acpi_match_table = ACPI_PTR(at24_acpi_ids),
        },
-- 
2.11.0