Re: [PATCH v1 1/1] iio: adc: nxp-sar-adc: Avoid division by zero

[Daniel Lezcano]

Hi Andy,

On 4/16/26 11:01, Andy Shevchenko wrote:
> When Common Clock Framework is disabled, clk_get_rate() returns 0.
> This is used as part of the divisor to perform nanosecond delays
> with help of ndelay(). When the above condition occurs the compiler,
> due to unspecified behaviour, is free to do what it wants to. Here
> it saturates the value, which is logical from mathematics point of
> view. However, the ndelay() implementation has set a reasonable
> upper threshold and refuses to provide anything for such a long
> delay. That's why code may not be linked under these circumstances.
>
> To solve the issue, provide a wrapper that calls ndelay() when
> the value is known not to be zero.
>
> Fixes: 4434072a893e ("iio: adc: Add the NXP SAR ADC support for the s32g2/3 platforms")
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Closes: https://lore.kernel.org/oe-kbuild-all/202603311958.ly6uROit-lkp@xxxxxxxxx/
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>

Acked-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxxxxxxxx>

> ---
>   drivers/iio/adc/nxp-sar-adc.c | 13 +++++++++++--
>   1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/adc/nxp-sar-adc.c b/drivers/iio/adc/nxp-sar-adc.c
> index 9d9f2c76bed4..705dd7da1bd2 100644
> --- a/drivers/iio/adc/nxp-sar-adc.c
> +++ b/drivers/iio/adc/nxp-sar-adc.c
> @@ -198,6 +198,15 @@ static void nxp_sar_adc_irq_cfg(struct nxp_sar_adc *info, bool enable)
>   		writel(0, NXP_SAR_ADC_IMR(info->regs));
>   }
>   
> +static void nxp_sar_adc_wait_for(struct nxp_sar_adc *info, unsigned int cycles)
> +{
> +	u64 rate;
> +
> +	rate = clk_get_rate(info->clk);
> +	if (rate)
> +		ndelay(div64_u64(NSEC_PER_SEC, rate * cycles));
> +}
> +
>   static bool nxp_sar_adc_set_enabled(struct nxp_sar_adc *info, bool enable)
>   {
>   	u32 mcr;
> @@ -221,7 +230,7 @@ static bool nxp_sar_adc_set_enabled(struct nxp_sar_adc *info, bool enable)
>   	 * configuration of NCMR and the setting of NSTART.
>   	 */
>   	if (enable)
> -		ndelay(div64_u64(NSEC_PER_SEC, clk_get_rate(info->clk) * 3));
> +		nxp_sar_adc_wait_for(info, 3);
>   
>   	return pwdn;
>   }
> @@ -469,7 +478,7 @@ static void nxp_sar_adc_stop_conversion(struct nxp_sar_adc *info)
>   	 * only when the capture finishes. The delay will be very
>   	 * short, usec-ish, which is acceptable in the atomic context.
>   	 */
> -	ndelay(div64_u64(NSEC_PER_SEC, clk_get_rate(info->clk)) * 80);
> +	nxp_sar_adc_wait_for(info, 80);
>   }
>   
>   static int nxp_sar_adc_start_conversion(struct nxp_sar_adc *info, bool raw)