[PATCH 3/5] iio: at91: ADC start-up time calculation changed since at91sam9x5

[Josh Wu]

On 7/20/2013 5:39 PM, Jonathan Cameron wrote:
> On 07/14/2013 09:04 AM, Josh Wu wrote:
>> Since in at91sam9x5, sama5d3x chip. the start up time calucation is changed.
>> And these two chips also have TSMR, so we check whether ADC has TSMR, then
>> choose different start up time calculation formula.
> If this doesn't have anything directly to do with the TSMR and this is just
> coincidence, then do this separately with it's own flag as it will be
> easier to maintain in the long run.

Agreed. I will fix it in next version.

Best Regards,
Josh Wu

>
> Jonathan
>> Signed-off-by: Josh Wu <josh.wu at atmel.com>
>> ---
>>   drivers/iio/adc/at91_adc.c |   40 +++++++++++++++++++++++++++++++++-------
>>   1 file changed, 33 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
>> index 14e99ba..e93a075 100644
>> --- a/drivers/iio/adc/at91_adc.c
>> +++ b/drivers/iio/adc/at91_adc.c
>> @@ -733,13 +733,39 @@ static int at91_adc_probe(struct platform_device *pdev)
>>   		goto error_disable_adc_clk;
>>   	}
>>   
>> -	/*
>> -	 * Number of ticks needed to cover the startup time of the ADC as
>> -	 * defined in the electrical characteristics of the board, divided by 8.
>> -	 * The formula thus is : Startup Time = (ticks + 1) * 8 / ADC Clock
>> -	 */
>> -	ticks = round_up((st->startup_time * adc_clk_khz /
>> -			  1000) - 1, 8) / 8;
>> +	if (!st->caps.has_tsmr) {
>> +		/*
>> +		 * Number of ticks needed to cover the startup time of the ADC
>> +		 * as defined in the electrical characteristics of the board,
>> +		 * divided by 8. The formula thus is :
>> +		 *   Startup Time = (ticks + 1) * 8 / ADC Clock
>> +		 */
>> +		ticks = round_up((st->startup_time * adc_clk_khz /
>> +				  1000) - 1, 8) / 8;
>> +	} else {
>> +		/*
>> +		 * For sama5d3x and at91sam9x5, the formula changes to:
>> +		 * Startup Time = <lookup_table_value> / ADC Clock
>> +		 */
>> +		const int startup_lookup[] = {
>> +			0  , 8  , 16 , 24 ,
>> +			64 , 80 , 96 , 112,
>> +			512, 576, 640, 704,
>> +			768, 832, 896, 960
>> +			};
>> +
>> +		int i, size = ARRAY_SIZE(startup_lookup);
>> +		ticks = st->startup_time * adc_clk_khz / 1000;
>> +		for (i = 0; i < size; i++)
>> +			if (ticks < startup_lookup[i])
>> +				break;
>> +
>> +		ticks = i;
>> +		if (ticks == size)
>> +			/* Reach the end of lookup table */
>> +			ticks = size - 1;
>> +	}
>> +
>>   	/*
>>   	 * a minimal Sample and Hold Time is necessary for the ADC to guarantee
>>   	 * the best converted final value between two channels selection
>>