Re: [PATCH 1/3] iio: at91: ADC start-up time calculation changed since at91sam9x5

[Jonathan Cameron <jic23@kernel.org>]

On 10/08/13 04:48, 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@atmel.com>
> Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Applied to the togreg branch of iio.git

Thanks
> ---
>  drivers/iio/adc/at91_adc.c |   53 ++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 46 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
> index 0f16b55..cee04a4 100644
> --- a/drivers/iio/adc/at91_adc.c
> +++ b/drivers/iio/adc/at91_adc.c
> @@ -40,6 +40,9 @@
>  	(writel_relaxed(val, st->reg_base + reg))
>  
>  struct at91_adc_caps {
> +	/* startup time calculate function */
> +	u32 (*calc_startup_ticks)(u8 startup_time, u32 adc_clk_khz);
> +
>  	struct at91_adc_reg_desc registers;
>  };
>  
> @@ -434,6 +437,45 @@ ret:
>  	return ret;
>  }
>  
> +static u32 calc_startup_ticks_9260(u8 startup_time, u32 adc_clk_khz)
> +{
> +	/*
> +	 * 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
> +	 */
> +	return round_up((startup_time * adc_clk_khz / 1000) - 1, 8) / 8;
> +}
> +
> +static u32 calc_startup_ticks_9x5(u8 startup_time, u32 adc_clk_khz)
> +{
> +	/*
> +	 * 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);
> +	unsigned int ticks;
> +
> +	ticks = 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;
> +
> +	return ticks;
> +}
> +
>  static const struct of_device_id at91_adc_dt_ids[];
>  
>  static int at91_adc_probe_dt(struct at91_adc_state *st,
> @@ -657,15 +699,9 @@ static int at91_adc_probe(struct platform_device *pdev)
>  		ret = -EINVAL;
>  		goto error_disable_adc_clk;
>  	}
> +	ticks = (*st->caps->calc_startup_ticks)(st->startup_time, adc_clk_khz);
>  
>  	/*
> -	 * 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;
> -	/*
>  	 * a minimal Sample and Hold Time is necessary for the ADC to guarantee
>  	 * the best converted final value between two channels selection
>  	 * The formula thus is : Sample and Hold Time = (shtim + 1) / ADCClock
> @@ -742,6 +778,7 @@ static int at91_adc_remove(struct platform_device *pdev)
>  
>  #ifdef CONFIG_OF
>  static struct at91_adc_caps at91sam9260_caps = {
> +	.calc_startup_ticks = calc_startup_ticks_9260,
>  	.registers = {
>  		.channel_base = AT91_ADC_CHR(0),
>  		.drdy_mask = AT91_ADC_DRDY,
> @@ -753,6 +790,7 @@ static struct at91_adc_caps at91sam9260_caps = {
>  };
>  
>  static struct at91_adc_caps at91sam9g45_caps = {
> +	.calc_startup_ticks = calc_startup_ticks_9260,	/* same as 9260 */
>  	.registers = {
>  		.channel_base = AT91_ADC_CHR(0),
>  		.drdy_mask = AT91_ADC_DRDY,
> @@ -764,6 +802,7 @@ static struct at91_adc_caps at91sam9g45_caps = {
>  };
>  
>  static struct at91_adc_caps at91sam9x5_caps = {
> +	.calc_startup_ticks = calc_startup_ticks_9x5,
>  	.registers = {
>  		.channel_base = AT91_ADC_CDR0_9X5,
>  		.drdy_mask = AT91_ADC_SR_DRDY_9X5,
>