iio: ti_am335x_adc: Fix wrong samples received on 1st read

Previously we tried to read data form ADC even before ADC sequencer
finished sampling. This led to wrong samples.
We now wait on ADC status register idle bit to be set.

Signed-off-by: Patil, Rachna <rachna@ti.com>
Signed-off-by: Zubair Lutfullah <zubair.lutfullah@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 22 insertions, 8 deletions

diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
index 0ad208a69c29..3ceac3e91dde 100644
--- a/drivers/iio/adc/ti_am335x_adc.c
+++ b/drivers/iio/adc/ti_am335x_adc.c
@@ -60,7 +60,6 @@ static void tiadc_step_config(struct tiadc_device *adc_dev)
 {
         unsigned int stepconfig;
         int i, steps;
-        u32 step_en;
 
         /*
          * There are 16 configurable steps and 8 analog input
@@ -86,8 +85,7 @@ static void tiadc_step_config(struct tiadc_device *adc_dev)
                 adc_dev->channel_step[i] = steps;
                 steps++;
         }
-        step_en = get_adc_step_mask(adc_dev);
-        am335x_tsc_se_set(adc_dev->mfd_tscadc, step_en);
+
 }
 
 static const char * const chan_name_ain[] = {
@@ -142,10 +140,22 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
                 int *val, int *val2, long mask)
 {
         struct tiadc_device *adc_dev = iio_priv(indio_dev);
-        int i;
-        unsigned int fifo1count, read;
+        int i, map_val;
+        unsigned int fifo1count, read, stepid;
         u32 step = UINT_MAX;
         bool found = false;
+        u32 step_en;
+        unsigned long timeout = jiffies + usecs_to_jiffies
+                                (IDLE_TIMEOUT * adc_dev->channels);
+        step_en = get_adc_step_mask(adc_dev);
+        am335x_tsc_se_set(adc_dev->mfd_tscadc, step_en);
+
+        /* Wait for ADC sequencer to complete sampling */
+        while (tiadc_readl(adc_dev, REG_ADCFSM) & SEQ_STATUS) {
+                if (time_after(jiffies, timeout))
+                        return -EAGAIN;
+                }
+        map_val = chan->channel + TOTAL_CHANNELS;
 
         /*
          * When the sub-system is first enabled,
@@ -170,12 +180,16 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
         fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
         for (i = 0; i < fifo1count; i++) {
                 read = tiadc_readl(adc_dev, REG_FIFO1);
-                if (read >> 16 == step) {
-                        *val = read & 0xfff;
+                stepid = read & FIFOREAD_CHNLID_MASK;
+                stepid = stepid >> 0x10;
+
+                if (stepid == map_val) {
+                        read = read & FIFOREAD_DATA_MASK;
                         found = true;
+                        *val = read;
                 }
         }
-        am335x_tsc_se_update(adc_dev->mfd_tscadc);
+
         if (found == false)
                 return -EBUSY;
         return IIO_VAL_INT;