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Date: Wed, 13 May 2015 13:12:35 +0530
From: Vignesh R <vigneshr@...com>
To: Jonathan Cameron <jic23@...nel.org>,
Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>
CC: Hartmut Knaack <knaack.h@....de>,
Lars-Peter Clausen <lars@...afoo.de>,
Peter Meerwald <pmeerw@...erw.net>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
Karol Wrona <k.wrona@...sung.com>,
Jan Kardell <jan.kardell@...liq.com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
"Cooper Jr., Franklin" <fcooper@...com>
Subject: Re: [PATCH 2/2] iio: adc: ti_am335x_adc: make sample delay, open
delay, averaging DT parameters
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@...com>
> All looks fine to me, but I would ideally like a devicetree
> ack on this one.
>
> Jonathan
Gentle ping...
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@...0d000 {
>> 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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