It can happen if a previous conversion was aborted the ADC pulls down
the ̅R̅D̅Y line but the event wasn't handled before. In that case enabling
the irq might immediately fire (depending on the irq controller's
capabilities) and even with a rdy-gpio isn't identified as an unrelated
one.
To cure that problem check for a pending event before the measurement is
started and clear it if needed.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxx>
---
drivers/iio/adc/ad_sigma_delta.c | 89 ++++++++++++++++++++++++++++++++
1 file changed, 89 insertions(+)
diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
index 9891346c2d73..164a4d0b571d 100644
--- a/drivers/iio/adc/ad_sigma_delta.c
+++ b/drivers/iio/adc/ad_sigma_delta.c
@@ -29,8 +29,11 @@
#define AD_SD_COMM_CHAN_MASK 0x3
#define AD_SD_REG_COMM 0x00
+#define AD_SD_REG_STATUS 0x00
#define AD_SD_REG_DATA 0x03
+#define AD_SD_REG_STATUS_RDY 0x80
+
/**
* ad_sd_set_comm() - Set communications register
*
@@ -222,6 +225,80 @@ static void ad_sd_enable_irq(struct ad_sigma_delta *sigma_delta)
enable_irq(sigma_delta->irq_line);
}
+/* Called with `sigma_delta->bus_locked == true` only. */
+static int ad_sigma_delta_clear_pending_event(struct ad_sigma_delta *sigma_delta)
+{
+ bool pending_event;
+ unsigned int data_read_len = BITS_TO_BYTES(sigma_delta->info->num_resetclks);
+ u8 data[9];
+ struct spi_transfer t[] = {
+ {
+ .tx_buf = data,
+ .len = 1,
+ }, {
+ .tx_buf = data + 1,
+ .len = data_read_len,
+ }
+ };
+ struct spi_message m;
+
+ /*
+ * read RDY pin (if possible) or status register to check if there is an
+ * old event.
+ */
+ if (sigma_delta->rdy_gpiod) {
+ pending_event = gpiod_get_value(sigma_delta->rdy_gpiod);
+ } else {
+ int ret;
+ unsigned status_reg;
+
+ ret = ad_sd_read_reg(sigma_delta, AD_SD_REG_STATUS, 1, &status_reg);
+ if (ret)
+ return ret;
+
+ pending_event = !(status_reg & AD_SD_REG_STATUS_RDY);
+ }
+
+ if (!pending_event)
+ return 0;
+
+ /*
+ * In general the size of the data register is unknown. It varies from
+ * device to device, might be one byte longer if CONTROL.DATA_STATUS is
+ * set and even varies on some devices depending on which input is
+ * selected. So send one byte to start reading the data register and
+ * then just clock for some bytes with DIN (aka MOSI) high to not
+ * confuse the register access state machine after the data register was
+ * completely read. Note however that the sequence length must be
+ * shorter than the reset procedure.
+ */
+
+ /* Oh, back out instead of overflowing data[] */
+ if (data_read_len > sizeof(data) - 1)
+ return -EINVAL;
+
+ spi_message_init(&m);
+ if (sigma_delta->info->has_registers) {
+ unsigned int data_reg = sigma_delta->info->data_reg ?: AD_SD_REG_DATA;
+
+ data[0] = data_reg << sigma_delta->info->addr_shift;
+ data[0] |= sigma_delta->info->read_mask;
+ data[0] |= sigma_delta->comm;
+ spi_message_add_tail(&t[0], &m);
+ }
+
+ /*
+ * The first transferred byte is part of the real data register,
+ * so this doesn't need to be 0xff. In the remaining
+ * `data_read_len - 1` bytes are less than $num_resetclks ones.
+ */
+ data[1] = 0x00;
+ memset(data + 2, 0xff, data_read_len - 1);
+ spi_message_add_tail(&t[1], &m);
+
+ return spi_sync_locked(sigma_delta->spi, &m);
+}
+
int ad_sd_calibrate(struct ad_sigma_delta *sigma_delta,
unsigned int mode, unsigned int channel)
{
@@ -237,6 +314,10 @@ int ad_sd_calibrate(struct ad_sigma_delta *sigma_delta,
sigma_delta->keep_cs_asserted = true;
reinit_completion(&sigma_delta->completion);
+ ret = ad_sigma_delta_clear_pending_event(sigma_delta);
+ if (ret)
+ return ret;
+
ret = ad_sigma_delta_set_mode(sigma_delta, mode);
if (ret < 0)
goto out;
@@ -310,6 +391,10 @@ int ad_sigma_delta_single_conversion(struct iio_dev *indio_dev,
sigma_delta->keep_cs_asserted = true;
reinit_completion(&sigma_delta->completion);
+ ret = ad_sigma_delta_clear_pending_event(sigma_delta);
+ if (ret)
+ return ret;
+
ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_SINGLE);
ad_sd_enable_irq(sigma_delta);
@@ -406,6 +491,10 @@ static int ad_sd_buffer_postenable(struct iio_dev *indio_dev)
sigma_delta->bus_locked = true;
sigma_delta->keep_cs_asserted = true;
+ ret = ad_sigma_delta_clear_pending_event(sigma_delta);
+ if (ret)
+ return ret;
+
ret = ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_CONTINUOUS);
if (ret)
goto err_unlock;
--
2.45.2
