Re: [PATCH 2/2] iio: adc: ti_am335x_adc: make sample delay, open delay, averaging DT parameters

From: Jonathan Cameron
Date: Wed May 13 2015 - 13:38:17 EST

On 13/05/15 08:42, Vignesh R wrote:
>
>
> On Thursday 09 April 2015 07:49 PM, Jonathan Cameron wrote:
>> On 31/03/15 12:12, Vignesh R wrote:
>>> 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@xxxxxx>
>> All looks fine to me, but I would ideally like a devicetree
>> ack on this one.
>>
>> Jonathan
>
> Gentle ping...
Thanks. Had forgotten about this one. Ah well, no device tree response...

Applied to the togreg branch of iio.git, initially pushed out as testing.

Thanks,

Jonathan
>
> Regards
> Vignesh
>>> ---
>>> .../bindings/input/touchscreen/ti-tsc-adc.txt | 24 ++++++++++
>>> drivers/iio/adc/ti_am335x_adc.c | 54 +++++++++++++++++++---
>>> 2 files changed, 72 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
>>> index 6c4fb34823d3..8aafbe87f0eb 100644
>>> --- a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
>>> +++ b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
>>> @@ -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>;
>>> };
>>> }
>>> diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
>>> index 2f818405ffbe..5ee597b4a1af 100644
>>> --- a/drivers/iio/adc/ti_am335x_adc.c
>>> +++ b/drivers/iio/adc/ti_am335x_adc.c
>>> @@ -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)alue 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. {
>>> + 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++;
>>> }
>>> @@ -407,9 +436,22 @@ 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;
>>> }
>>>
>>
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