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Commit 5dc11e81 authored by Vignesh R's avatar Vignesh R Committed by Jonathan Cameron
Browse files

iio: adc: ti_am335x_adc: make sample delay, open delay, averaging DT parameters 



Add optional DT properties to set open delay, sample delay and number
of averages per sample for each adc step. Open delay, sample delay
and averaging are some of the parameters that affect the sampling rate
and accuracy of the sample. Making these parameters configurable via
DT will help in balancing speed vs accuracy.

Signed-off-by: default avatarVignesh R <vigneshr@ti.com>
Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
parent feca56ff

Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt

+24 −0
Original line number Original line Diff line number Diff line
@@ -42,6 +42,27 @@ Optional properties: 
			 hardware knob for adjusting the amount of "settling

			 hardware knob for adjusting the amount of "settling

			 time".

			 time".





- child "adc"

	ti,chan-step-opendelay: List of open delays for each channel of

				ADC in the order of ti,adc-channels. The

				value corresponds to the number of ADC

				clock cycles to wait after applying the

				step configuration registers and before

				sending the start of ADC conversion.

				Maximum value is 0x3FFFF.

       ti,chan-step-sampledelay: List of sample delays for each channel

				  of ADC in the order of ti,adc-channels.

				  The value corresponds to the number of

				  ADC clock cycles to sample (to hold

				  start of conversion high).

				  Maximum value is 0xFF.

       ti,chan-step-avg: Number of averages to be performed for each

			  channel of ADC. If average is 16 then input

			  is sampled 16 times and averaged to get more

			  accurate value. This increases the time taken

			  by ADC to generate a sample. Valid range is 0

			  average to 16 averages. Maximum value is 16.



Example:

Example:

	tscadc: tscadc@44e0d000 {

	tscadc: tscadc@44e0d000 {

		compatible = "ti,am3359-tscadc";

		compatible = "ti,am3359-tscadc";
@@ -55,5 +76,8 @@ Example: 




		adc {

		adc {

			ti,adc-channels = <4 5 6 7>;

			ti,adc-channels = <4 5 6 7>;

			ti,chan-step-opendelay = <0x098 0x3ffff 0x098 0x0>;

			ti,chan-step-sampledelay = <0xff 0x0 0xf 0x0>;

			ti,chan-step-avg = <16 2 4 8>;

		};

		};

	}
 
	}

drivers/iio/adc/ti_am335x_adc.c

+48 −6
Original line number Original line Diff line number Diff line
@@ -37,6 +37,7 @@ struct tiadc_device { 
	u8 channel_step[8];

	u8 channel_step[8];

	int buffer_en_ch_steps;

	int buffer_en_ch_steps;

	u16 data[8];

	u16 data[8];

	u32 open_delay[8], sample_delay[8], step_avg[8];

};

};





static unsigned int tiadc_readl(struct tiadc_device *adc, unsigned int reg)

static unsigned int tiadc_readl(struct tiadc_device *adc, unsigned int reg)
@@ -85,6 +86,7 @@ static u32 get_adc_step_bit(struct tiadc_device *adc_dev, int chan) 
static void tiadc_step_config(struct iio_dev *indio_dev)

static void tiadc_step_config(struct iio_dev *indio_dev)

{

{

	struct tiadc_device *adc_dev = iio_priv(indio_dev);

	struct tiadc_device *adc_dev = iio_priv(indio_dev);

	struct device *dev = adc_dev->mfd_tscadc->dev;

	unsigned int stepconfig;

	unsigned int stepconfig;

	int i, steps = 0;

	int i, steps = 0;
@@ -98,20 +100,47 @@ static void tiadc_step_config(struct iio_dev *indio_dev) 
	 * needs to be given to ADC to digitalize data.

	 * needs to be given to ADC to digitalize data.

	 */

	 */





	if (iio_buffer_enabled(indio_dev))

		stepconfig = STEPCONFIG_AVG_16 | STEPCONFIG_FIFO1

					| STEPCONFIG_MODE_SWCNT;

	else

		stepconfig = STEPCONFIG_AVG_16 | STEPCONFIG_FIFO1;





	for (i = 0; i < adc_dev->channels; i++) {

	for (i = 0; i < adc_dev->channels; i++) {

		int chan;

		int chan;





		chan = adc_dev->channel_line[i];

		chan = adc_dev->channel_line[i];



		if (adc_dev->step_avg[i] > STEPCONFIG_AVG_16) {

			dev_warn(dev, "chan %d step_avg truncating to %d\n",

				 chan, STEPCONFIG_AVG_16);

			adc_dev->step_avg[i] = STEPCONFIG_AVG_16;

		}



		if (adc_dev->step_avg[i])

			stepconfig =

			STEPCONFIG_AVG(ffs(adc_dev->step_avg[i]) - 1) |

			STEPCONFIG_FIFO1;

		else

			stepconfig = STEPCONFIG_FIFO1;



		if (iio_buffer_enabled(indio_dev))

			stepconfig |= STEPCONFIG_MODE_SWCNT;



		tiadc_writel(adc_dev, REG_STEPCONFIG(steps),

		tiadc_writel(adc_dev, REG_STEPCONFIG(steps),

				stepconfig | STEPCONFIG_INP(chan));

				stepconfig | STEPCONFIG_INP(chan));



		if (adc_dev->open_delay[i] > STEPDELAY_OPEN_MASK) {

			dev_warn(dev, "chan %d open delay truncating to 0x3FFFF\n",

				 chan);

			adc_dev->open_delay[i] = STEPDELAY_OPEN_MASK;

		}



		if (adc_dev->sample_delay[i] > 0xFF) {

			dev_warn(dev, "chan %d sample delay truncating to 0xFF\n",

				 chan);

			adc_dev->sample_delay[i] = 0xFF;

		}



		tiadc_writel(adc_dev, REG_STEPDELAY(steps),

		tiadc_writel(adc_dev, REG_STEPDELAY(steps),

				STEPCONFIG_OPENDLY);

				STEPDELAY_OPEN(adc_dev->open_delay[i]) |

				STEPDELAY_SAMPLE(adc_dev->sample_delay[i]));



		adc_dev->channel_step[i] = steps;

		adc_dev->channel_step[i] = steps;

		steps++;

		steps++;

	}

	}
@@ -406,9 +435,22 @@ static int tiadc_parse_dt(struct platform_device *pdev, 




	of_property_for_each_u32(node, "ti,adc-channels", prop, cur, val) {

	of_property_for_each_u32(node, "ti,adc-channels", prop, cur, val) {

		adc_dev->channel_line[channels] = val;

		adc_dev->channel_line[channels] = val;



		/* Set Default values for optional DT parameters */

		adc_dev->open_delay[channels] = STEPCONFIG_OPENDLY;

		adc_dev->sample_delay[channels] = STEPCONFIG_SAMPLEDLY;

		adc_dev->step_avg[channels] = 16;



		channels++;

		channels++;

	}

	}





	of_property_read_u32_array(node, "ti,chan-step-avg",

				   adc_dev->step_avg, channels);

	of_property_read_u32_array(node, "ti,chan-step-opendelay",

				   adc_dev->open_delay, channels);

	of_property_read_u32_array(node, "ti,chan-step-sampledelay",

				   adc_dev->sample_delay, channels);



	adc_dev->channels = channels;

	adc_dev->channels = channels;

	return 0;

	return 0;

}

}