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@xxxxxxxxx>
> ---
> 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?
Maxime
--
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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