From: Adam Wujek dev_public@wujek.eu
[ Upstream commit d1baf7a3a3177d46a7149858beddb88a9eca7a54 ]
Make sure that the support of PEC is determined before the read of other registers. Otherwise the validation of PEC can trigger an error on the read of STATUS_BYTE or STATUS_WORD registers.
The problematic scenario is the following. A device with enabled PEC support is up and running and a kernel driver is loaded. Then the driver is unloaded (or device unbound), the HW device is reconfigured externally (e.g. by i2cset) to advertise itself as not supporting PEC. Without the move of the code, at the second load of the driver (or bind) the STATUS_BYTE or STATUS_WORD register is always read with PEC enabled, which is likely to cause a read error resulting with fail of a driver load (or bind).
Signed-off-by: Adam Wujek dev_public@wujek.eu Link: https://lore.kernel.org/r/20220519233334.438621-1-dev_public@wujek.eu Fixes: 75d2b2b06bd84 ("hwmon: (pmbus) disable PEC if not enabled") Fixes: 4e5418f787ec5 ("hwmon: (pmbus_core) Check adapter PEC support") [groeck: Added Fixes: tags, dropped continuation line] Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/hwmon/pmbus/pmbus_core.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-)
diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c index 5f8f824d997f..63b616ce3a6e 100644 --- a/drivers/hwmon/pmbus/pmbus_core.c +++ b/drivers/hwmon/pmbus/pmbus_core.c @@ -2308,6 +2308,21 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data, struct device *dev = &client->dev; int page, ret;
+ /* + * Figure out if PEC is enabled before accessing any other register. + * Make sure PEC is disabled, will be enabled later if needed. + */ + client->flags &= ~I2C_CLIENT_PEC; + + /* Enable PEC if the controller and bus supports it */ + if (!(data->flags & PMBUS_NO_CAPABILITY)) { + ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY); + if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK)) { + if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_PEC)) + client->flags |= I2C_CLIENT_PEC; + } + } + /* * Some PMBus chips don't support PMBUS_STATUS_WORD, so try * to use PMBUS_STATUS_BYTE instead if that is the case. @@ -2326,19 +2341,6 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data, data->has_status_word = true; }
- /* Make sure PEC is disabled, will be enabled later if needed */ - client->flags &= ~I2C_CLIENT_PEC; - - /* Enable PEC if the controller and bus supports it */ - if (!(data->flags & PMBUS_NO_CAPABILITY)) { - ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY); - if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK)) { - if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_PEC)) { - client->flags |= I2C_CLIENT_PEC; - } - } - } - /* * Check if the chip is write protected. If it is, we can not clear * faults, and we should not try it. Also, in that case, writes into