linux-kernel - Re: [PATCH] iio: adc: at91_adc: correct default shtim value

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Date:	Wed, 5 Mar 2014 19:04:58 +0800
From:	Josh Wu <josh.wu@...el.com>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Jonathan Cameron <jic23@...nel.org>
CC:	<linux-kernel@...r.kernel.org>, <linux-iio@...r.kernel.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Ludovic Desroches <ludovic.desroches@...el.com>
Subject: Re: [PATCH] iio: adc: at91_adc: correct default shtim value

Hi, Alexandre

On 3/4/2014 2:07 AM, Alexandre Belloni wrote:
> When sample_hold_time is zero (this is the case when DT is not used or if
> atmel,adc-sample-hold-time is omitted), then the calculated shtim is large.
>
> Make that 0, which is the default for that register and the ADC will then use a
> sane value of 2/ADCCLK or 1/ADCCLK depending on the version.
>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>

Thanks for the fix and

Acked-by: Josh Wu<josh.wu@...el.com>

Best Regards,
Josh Wu
> ---
>   drivers/iio/adc/at91_adc.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
> index 5b1aa027c034..0b103f905607 100644
> --- a/drivers/iio/adc/at91_adc.c
> +++ b/drivers/iio/adc/at91_adc.c
> @@ -1004,8 +1004,11 @@ static int at91_adc_probe(struct platform_device *pdev)
>   	 * the best converted final value between two channels selection
>   	 * The formula thus is : Sample and Hold Time = (shtim + 1) / ADCClock
>   	 */
> -	shtim = round_up((st->sample_hold_time * adc_clk_khz /
> -			  1000) - 1, 1);
> +	if (st->sample_hold_time > 0)
> +		shtim = round_up((st->sample_hold_time * adc_clk_khz / 1000)
> +				 - 1, 1);
> +	else
> +		shtim = 0;
>   
>   	reg = AT91_ADC_PRESCAL_(prsc) & st->registers->mr_prescal_mask;
>   	reg |= AT91_ADC_STARTUP_(ticks) & st->registers->mr_startup_mask;

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