linux-kernel - Re: [PATCH 1/4] iio: ti_am335x_adc: Fix wrong samples received on 1st read

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Date:	Sun, 21 Jul 2013 18:28:38 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Zubair Lutfullah <zubair.lutfullah@...il.com>
CC:	sameo@...ux.intel.com, lee.jones@...aro.org,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org, koen@...inion.thruhere.net
Subject: Re: [PATCH 1/4] iio: ti_am335x_adc: Fix wrong samples received on
 1st read

On 07/20/2013 05:27 PM, Zubair Lutfullah wrote:
> From: "Patil, Rachna" <rachna@...com>
> 
> Previously we tried to read data form ADC even before ADC sequencer
> finished sampling. This led to wrong samples.
> We now wait on ADC status register idle bit to be set.
> 
> Signed-off-by: Patil, Rachna <rachna@...com>
> Signed-off-by: Zubair Lutfullah <zubair.lutfullah@...il.com>
> Acked-by: Jonathan Cameron <jic23@...nel.org>

Applied this one to the fixes-togreg branch of iio.git.

I'd imagine the others will go through mfd?
> ---
>  drivers/iio/adc/ti_am335x_adc.c      |   30 ++++++++++++++++++++++--------
>  include/linux/mfd/ti_am335x_tscadc.h |   16 ++++++++++++++++
>  2 files changed, 38 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
> index 4427e8e..f73fee1 100644
> --- a/drivers/iio/adc/ti_am335x_adc.c
> +++ b/drivers/iio/adc/ti_am335x_adc.c
> @@ -60,7 +60,6 @@ static void tiadc_step_config(struct tiadc_device *adc_dev)
>  {
>  	unsigned int stepconfig;
>  	int i, steps;
> -	u32 step_en;
>  
>  	/*
>  	 * There are 16 configurable steps and 8 analog input
> @@ -86,8 +85,7 @@ static void tiadc_step_config(struct tiadc_device *adc_dev)
>  		adc_dev->channel_step[i] = steps;
>  		steps++;
>  	}
> -	step_en = get_adc_step_mask(adc_dev);
> -	am335x_tsc_se_set(adc_dev->mfd_tscadc, step_en);
> +
>  }
>  
>  static const char * const chan_name_ain[] = {
> @@ -142,10 +140,22 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
>  		int *val, int *val2, long mask)
>  {
>  	struct tiadc_device *adc_dev = iio_priv(indio_dev);
> -	int i;
> -	unsigned int fifo1count, read;
> +	int i, map_val;
> +	unsigned int fifo1count, read, stepid;
>  	u32 step = UINT_MAX;
>  	bool found = false;
> +	u32 step_en;
> +	unsigned long timeout = jiffies + usecs_to_jiffies
> +				(IDLE_TIMEOUT * adc_dev->channels);
> +	step_en = get_adc_step_mask(adc_dev);
> +	am335x_tsc_se_set(adc_dev->mfd_tscadc, step_en);
> +
> +	/* Wait for ADC sequencer to complete sampling */
> +	while (tiadc_readl(adc_dev, REG_ADCFSM) & SEQ_STATUS) {
> +		if (time_after(jiffies, timeout))
> +			return -EAGAIN;
> +		}
> +	map_val = chan->channel + TOTAL_CHANNELS;
>  
>  	/*
>  	 * When the sub-system is first enabled,
> @@ -170,12 +180,16 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
>  	fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
>  	for (i = 0; i < fifo1count; i++) {
>  		read = tiadc_readl(adc_dev, REG_FIFO1);
> -		if (read >> 16 == step) {
> -			*val = read & 0xfff;
> +		stepid = read & FIFOREAD_CHNLID_MASK;
> +		stepid = stepid >> 0x10;
> +
> +		if (stepid == map_val) {
> +			read = read & FIFOREAD_DATA_MASK;
>  			found = true;
> +			*val = read;
>  		}
>  	}
> -	am335x_tsc_se_update(adc_dev->mfd_tscadc);
> +
>  	if (found == false)
>  		return -EBUSY;
>  	return IIO_VAL_INT;
> diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h
> index 8d73fe2..db1791b 100644
> --- a/include/linux/mfd/ti_am335x_tscadc.h
> +++ b/include/linux/mfd/ti_am335x_tscadc.h
> @@ -113,11 +113,27 @@
>  #define CNTRLREG_8WIRE		CNTRLREG_AFE_CTRL(3)
>  #define CNTRLREG_TSCENB		BIT(7)
>  
> +/* FIFO READ Register */
> +#define FIFOREAD_DATA_MASK (0xfff << 0)
> +#define FIFOREAD_CHNLID_MASK (0xf << 16)
> +
> +/* Sequencer Status */
> +#define SEQ_STATUS BIT(5)
> +
>  #define ADC_CLK			3000000
>  #define	MAX_CLK_DIV		7
>  #define TOTAL_STEPS		16
>  #define TOTAL_CHANNELS		8
>  
> +/*
> +* ADC runs at 3MHz, and it takes
> +* 15 cycles to latch one data output.
> +* Hence the idle time for ADC to
> +* process one sample data would be
> +* around 5 micro seconds.
> +*/
> +#define IDLE_TIMEOUT 5 /* microsec */
> +
>  #define TSCADC_CELLS		2
>  
>  struct ti_tscadc_dev {
> 
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