[PATCH v2 3/4] iio: at91: ADC start-up time calculation changed since at91sam9x5
Josh Wu
josh.wu at atmel.com
Thu Aug 22 05:54:16 EDT 2013
Hi, Maxime
On 8/16/2013 3:27 AM, Maxime Ripard wrote:
> Hi Josh,
>
> On Sun, Aug 11, 2013 at 07:04:30PM +0800, Josh Wu wrote:
>> Since in at91sam9x5, sama5d3x chip. the start up time calucation is
>> changed. This patch can choose different start up time calculation
>> formula for different chips.
>>
>> Signed-off-by: Josh Wu <josh.wu at atmel.com>
>> ---
>> v1 --> v2:
>> add a new variable for different start_time calculation.
>>
>> drivers/iio/adc/at91_adc.c | 42 +++++++++++++++++++++++++++++++++++-------
>> 1 file changed, 35 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
>> index b41eb60..9b0ffff 100644
>> --- a/drivers/iio/adc/at91_adc.c
>> +++ b/drivers/iio/adc/at91_adc.c
>> @@ -40,6 +40,7 @@
>> (writel_relaxed(val, st->reg_base + reg))
>>
>> struct at91_adc_caps {
>> + bool start_time_use_lookup_tab;
>> u32 mr_prescal_mask;
>> u32 mr_startup_mask;
>> };
>> @@ -700,13 +701,39 @@ 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->start_time_use_lookup_tab) {
>> + /*
>> + * 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;
>> + }
>> +
> Maybe just declaring two different functions here to calculate the
> number of ticks, and just holding the function pointer in your structure
> would make things more readable and future-proof?
I'll do this in next version. thanks.
>
> Maxime
>
Best Regards,
Josh Wu
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