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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: Vignesh R <vigneshr@ti.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Vignesh R 2015-03-31 16:42:37 +05:30 committed by Jonathan Cameron
parent feca56ff40
commit 5dc11e8106
2 changed files with 72 additions and 6 deletions
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24
Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
View File

@ -42,6 +42,27 @@ Optional properties:
hardware knob for adjusting the amount of "settling
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:
tscadc: tscadc@44e0d000 {
compatible = "ti,am3359-tscadc";
@ -55,5 +76,8 @@ Example:
adc {
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>;
};
}

54
drivers/iio/adc/ti_am335x_adc.c
View File

@ -37,6 +37,7 @@ struct tiadc_device {
u8 channel_step[8];
int buffer_en_ch_steps;
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)
@ -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)
{
struct tiadc_device *adc_dev = iio_priv(indio_dev);
struct device *dev = adc_dev->mfd_tscadc->dev;
unsigned int stepconfig;
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.
*/
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++) {
int chan;
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),
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),
STEPCONFIG_OPENDLY);
STEPDELAY_OPEN(adc_dev->open_delay[i]) |
STEPDELAY_SAMPLE(adc_dev->sample_delay[i]));
adc_dev->channel_step[i] = 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) {
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++;
}
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;
return 0;
}