Re: [PATCH v8 2/3] thermal/drivers/imx: Fix rounding and clamp for i.MX7D alarm

[Frank Li]

On Tue, Jul 14, 2026 at 06:28:42PM +0800, Haoning CHENG via B4 Relay wrote:
> From: Haoning CHENG <Haoning.CHENG@xxxxxxxxxxxx>
>
> Convert the alarm temperature from millicelsius to degrees for i.MX7D
> using ceiling division instead of integer division, ensuring rounding
> errors do not cause the alarm to trigger below the intended threshold.
> Use DIV_ROUND_UP() for non-negative values and plain integer division
> for negative values, since C rounds toward zero which is equivalent to
> ceiling when the divisor is positive.
>
> Add clamp() to ensure the hardware register value stays within the 9-bit
> range (0..0x1ff) of the i.MX7D alarm field, preventing silent truncation
> if an out-of-range value is written.
>
> Signed-off-by: Haoning CHENG <Haoning.CHENG@xxxxxxxxxxxx>
> ---

Reviewed-by: Frank Li <Frank.Li@xxxxxxx>

>  drivers/thermal/imx_thermal.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/thermal/imx_thermal.c b/drivers/thermal/imx_thermal.c
> index 38c993d1bcb3..7f7d1116b9d6 100644
> --- a/drivers/thermal/imx_thermal.c
> +++ b/drivers/thermal/imx_thermal.c
> @@ -240,10 +240,16 @@ static void imx_set_alarm_temp(struct imx_thermal_data *data,
>
>  	data->alarm_temp = alarm_temp;
>
> -	if (data->socdata->version == TEMPMON_IMX7D)
> -		alarm_value = alarm_temp / 1000 + data->c1 - 25;
> -	else
> +	if (data->socdata->version == TEMPMON_IMX7D) {
> +		if (alarm_temp >= 0)
> +			alarm_temp = DIV_ROUND_UP(alarm_temp, 1000);
> +		else
> +			alarm_temp /= 1000;
> +		alarm_value = alarm_temp + data->c1 - 25;
> +		alarm_value = clamp(alarm_value, 0, 0x1ff);
> +	} else {
>  		alarm_value = (data->c2 - alarm_temp) / data->c1;
> +	}
>
>  	regmap_write(map, soc_data->high_alarm_ctrl + REG_CLR,
>  		     soc_data->high_alarm_mask);
>
> --
> 2.43.0
>
>
>