[PATCH] iio: adc: at91_adc: correct default shtim value

[PATCH] iio: adc: at91_adc: correct default shtim value

[Alexandre Belloni]

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@free-electrons.com>
---
 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;
-- 
1.8.3.2

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

[Josh Wu]

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@free-electrons.com>

Thanks for the fix and

Acked-by: Josh Wu<josh.wu@atmel.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;

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

[Jonathan Cameron]

On 05/03/14 11:04, Josh Wu wrote:
> 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@free-electrons.com>
>
> Thanks for the fix and
>
> Acked-by: Josh Wu<josh.wu@atmel.com>
>
Applied to the fixes-togreg branch of iio.git.
Note that is likely that this will go upstream after the merge window now.

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

[Alexandre Belloni]

Hi,

On 15/03/2014 at 16:34:02 +0000, Jonathan Cameron wrote :
> Applied to the fixes-togreg branch of iio.git.
> Note that is likely that this will go upstream after the merge window now.
> 

I was aiming at 3.15 anyway.

Thanks for you help !

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com