[RFC PATCH 1/1] hwmon: emc2305: Set max PWM state during shutdown

[Guenter Roeck]

On 3/6/26 05:34, florin.leotescu at oss.nxp.com wrote:
> From: Florin Leotescu <florin.leotescu at nxp.com>
> 
> Some platforms rely on Linux to leave the EMC2305 fan controller in a
> safe fan state before the system restart handoff.
> 
> If a soft reboot is initiated, the controller may retain the last PWM
> duty cycle written by the kernel until another software stage
> reconfigures it. On systems where no later stage immediately takes over
> fan control, this may leave the fans running below a desired fail-safe
> level.
> 
> Signed-off-by: Florin Leotescu <florin.leotescu at nxp.com>
> ---
>   drivers/hwmon/emc2305.c | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/hwmon/emc2305.c b/drivers/hwmon/emc2305.c
> index 64b213e1451e..d631d972c40e 100644
> --- a/drivers/hwmon/emc2305.c
> +++ b/drivers/hwmon/emc2305.c
> @@ -714,6 +714,20 @@ static int emc2305_probe(struct i2c_client *client)
>   	return 0;
>   }
>   
> +static void emc2305_shutdown(struct i2c_client *client)
> +{
> +	int i;
> +	int ret;
> +	struct emc2305_data *data = i2c_get_clientdata(client);
> +
> +	for (i = 0; i < data->pwm_num; i++) {
> +		ret = i2c_smbus_write_byte_data(client, EMC2305_REG_FAN_DRIVE(i), EMC2305_FAN_MAX);
> +		if (ret < 0)
> +			dev_warn(&client->dev,
> +				 "Failed to set max PWM on for ch %d during shudown", i);

s/shudown/shutdown, and newline missing

> +	}
> +}
> +

We can not do this unconditionally. This would have to be configurable.
The driver could use the optional fan-shutdown-percent devicetree
property for that purpose.

Thanks,
Guenter