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>

1 files changed, 48 insertions, 6 deletions

diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
index 42e444044ea5..942320e32753 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) {
+                        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;
 }