mfd: input: iio: ti_amm335x: Rework TSC/ADC synchronization

[~andy/linux] / drivers / iio / adc / ti_am335x_adc.c

diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
index e0dc2d0e7590a4206b8d3c0a90a35e8a0aeea395..dff7343405e2f752e93aaf16d61e4d2220b6b9f0 100644 (file)
--- a/drivers/iio/adc/ti_am335x_adc.c
+++ b/drivers/iio/adc/ti_am335x_adc.c
@@ -60,6 +60,24 @@ static u32 get_adc_step_mask(struct tiadc_device *adc_dev)
        return step_en;
 }
 
+static u32 get_adc_chan_step_mask(struct tiadc_device *adc_dev,
+               struct iio_chan_spec const *chan)
+{
+       int i;
+
+       for (i = 0; i < ARRAY_SIZE(adc_dev->channel_step); i++) {
+               if (chan->channel == adc_dev->channel_line[i]) {
+                       u32 step;
+
+                       step = adc_dev->channel_step[i];
+                       /* +1 for the charger */
+                       return 1 << (step + 1);
+               }
+       }
+       WARN_ON(1);
+       return 0;
+}
+
 static u32 get_adc_step_bit(struct tiadc_device *adc_dev, int chan)
 {
        return 1 << adc_dev->channel_step[chan];
@@ -326,34 +344,43 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
        unsigned int fifo1count, read, stepid;
        bool found = false;
        u32 step_en;
-       unsigned long timeout = jiffies + usecs_to_jiffies
-                               (IDLE_TIMEOUT * adc_dev->channels);
+       unsigned long timeout;
 
        if (iio_buffer_enabled(indio_dev))
                return -EBUSY;
 
-       step_en = get_adc_step_mask(adc_dev);
+       step_en = get_adc_chan_step_mask(adc_dev, chan);
+       if (!step_en)
+               return -EINVAL;
+
+       fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
+       while (fifo1count--)
+               tiadc_readl(adc_dev, REG_FIFO1);
+
        am335x_tsc_se_set_once(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))
+       timeout = jiffies + usecs_to_jiffies
+                               (IDLE_TIMEOUT * adc_dev->channels);
+       /* Wait for Fifo threshold interrupt */
+       while (1) {
+               fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
+               if (fifo1count)
+                       break;
+
+               if (time_after(jiffies, timeout)) {
+                       am335x_tsc_se_adc_done(adc_dev->mfd_tscadc);
                        return -EAGAIN;
+               }
        }
        map_val = chan->channel + TOTAL_CHANNELS;
 
        /*
-        * When the sub-system is first enabled,
-        * the sequencer will always start with the
-        * lowest step (1) and continue until step (16).
-        * For ex: If we have enabled 4 ADC channels and
-        * currently use only 1 out of them, the
-        * sequencer still configures all the 4 steps,
-        * leading to 3 unwanted data.
-        * Hence we need to flush out this data.
+        * We check the complete FIFO. We programmed just one entry but in case
+        * something went wrong we left empty handed (-EAGAIN previously) and
+        * then the value apeared somehow in the FIFO we would have two entries.
+        * Therefore we read every item and keep only the latest version of the
+        * requested channel.
         */
-
-       fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
        for (i = 0; i < fifo1count; i++) {
                read = tiadc_readl(adc_dev, REG_FIFO1);
                stepid = read & FIFOREAD_CHNLID_MASK;
@@ -365,6 +392,7 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
                        *val = (u16) read;
                }
        }
+       am335x_tsc_se_adc_done(adc_dev->mfd_tscadc);
 
        if (found == false)
                return -EBUSY;
@@ -492,8 +520,8 @@ static int tiadc_resume(struct device *dev)
        tiadc_writel(adc_dev, REG_CTRL, restore);
 
        tiadc_step_config(indio_dev);
-       am335x_tsc_se_set(adc_dev->mfd_tscadc, adc_dev->buffer_en_ch_steps);
-
+       am335x_tsc_se_set_cache(adc_dev->mfd_tscadc,
+                       adc_dev->buffer_en_ch_steps);
        return 0;
 }