Some platforms (e.g. IBM Power System S822LC (8335-GCA POWER8)) do not
describe the EEPROM’s VCC supply in firmware-provided device trees.
Using `devm_regulator_get()` on such systems falls back to a dummy
regulator with a kernel warning:
at24 0-0051: supply vcc not found, using dummy regulator
at24 0-0051: 16384 byte 24c128 EEPROM, writable, 1 bytes/write
at24 0-0052: supply vcc not found, using dummy regulator
at24 0-0052: 256 byte 24c02 EEPROM, writable, 1 bytes/write
at24 0-0053: supply vcc not found, using dummy regulator
at24 0-0053: 256 byte 24c02 EEPROM, writable, 1 bytes/write
at24 0-0054: supply vcc not found, using dummy regulator
at24 0-0054: 256 byte 24c02 EEPROM, writable, 1 bytes/write
[…]
at24 12-0050: supply vcc not found, using dummy regulator
at24 12-0050: 16384 byte 24c128 EEPROM, writable, 1 bytes/write
at24 12-0051: supply vcc not found, using dummy regulator
at24 12-0051: 16384 byte 24c128 EEPROM, writable, 1 bytes/write
Switch to `devm_regulator_get_optional()` and treat -ENODEV as “no
supply described”. When `vcc_reg` is NULL, skip all
regulator_enable/disable calls; the hardware is assumed to be always
powered. Linux now logs:
at24 0-0051: 16384 byte 24c128 EEPROM, writable, 1 bytes/write
at24 0-0052: 256 byte 24c02 EEPROM, writable, 1 bytes/write
at24 0-0053: 256 byte 24c02 EEPROM, writable, 1 bytes/write
at24 0-0054: 256 byte 24c02 EEPROM, writable, 1 bytes/write
at24 0-0055: 256 byte 24c02 EEPROM, writable, 1 bytes/write
[…]
at24 12-0050: 16384 byte 24c128 EEPROM, writable, 1 bytes/write
at24 12-0051: 16384 byte 24c128 EEPROM, writable, 1 bytes/write
Assisted-by: Claude Sonnet 4.6
Cc: Madhavan Srinivasan <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: [email protected]
Signed-off-by: Paul Menzel <[email protected]>
---
drivers/misc/eeprom/at24.c | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)
diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 0200288d3a7a..7e1050f8759a 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -699,9 +699,12 @@ static int at24_probe(struct i2c_client *client)
at24->offset_adj = at24_get_offset_adj(flags, byte_len);
at24->client_regmaps[0] = regmap;
- at24->vcc_reg = devm_regulator_get(dev, "vcc");
- if (IS_ERR(at24->vcc_reg))
- return PTR_ERR(at24->vcc_reg);
+ at24->vcc_reg = devm_regulator_get_optional(dev, "vcc");
+ if (IS_ERR(at24->vcc_reg)) {
+ if (PTR_ERR(at24->vcc_reg) != -ENODEV)
+ return PTR_ERR(at24->vcc_reg);
+ at24->vcc_reg = NULL;
+ }
writable = !(flags & AT24_FLAG_READONLY);
if (writable) {
@@ -754,9 +757,12 @@ static int at24_probe(struct i2c_client *client)
full_power = acpi_dev_state_d0(&client->dev);
if (full_power) {
- err = regulator_enable(at24->vcc_reg);
- if (err)
- return dev_err_probe(dev, err, "Failed to enable vcc
regulator\n");
+ if (at24->vcc_reg) {
+ err = regulator_enable(at24->vcc_reg);
+ if (err) {
+ return dev_err_probe(dev, err, "Failed to
enable vcc regulator\n");
+ }
+ }
pm_runtime_set_active(dev);
}
@@ -771,7 +777,7 @@ static int at24_probe(struct i2c_client *client)
err = at24_read(at24, 0, &test_byte, 1);
if (err) {
pm_runtime_disable(dev);
- if (!pm_runtime_status_suspended(dev))
+ if (!pm_runtime_status_suspended(dev) && at24->vcc_reg)
regulator_disable(at24->vcc_reg);
return -ENODEV;
}
@@ -808,7 +814,7 @@ static void at24_remove(struct i2c_client *client)
pm_runtime_disable(&client->dev);
if (acpi_dev_state_d0(&client->dev)) {
- if (!pm_runtime_status_suspended(&client->dev))
+ if (!pm_runtime_status_suspended(&client->dev) && at24->vcc_reg)
regulator_disable(at24->vcc_reg);
pm_runtime_set_suspended(&client->dev);
}
@@ -819,6 +825,8 @@ static int __maybe_unused at24_suspend(struct device *dev)
struct i2c_client *client = to_i2c_client(dev);
struct at24_data *at24 = i2c_get_clientdata(client);
+ if (!at24->vcc_reg)
+ return 0;
return regulator_disable(at24->vcc_reg);
}
@@ -827,6 +835,8 @@ static int __maybe_unused at24_resume(struct device *dev)
struct i2c_client *client = to_i2c_client(dev);
struct at24_data *at24 = i2c_get_clientdata(client);
+ if (!at24->vcc_reg)
+ return 0;
return regulator_enable(at24->vcc_reg);
}
--
2.53.0
