[PATCH 5.14 041/432] iio: ltc2983: fix device probe

Greg Kroah-Hartman
2021-09-16T17:14:19Z

From: Nuno Sá <nuno.sa@analog.com>

commit b76d26d69ecc97ebb24aaf40427a13c808a4f488 upstream.

There is no reason to assume that the IRQ rising edge (indicating that
the device start up phase is done) will happen after we request the IRQ.
If the device is already up by the time we request it, the call to
'wait_for_completion_timeout()' will timeout and we will fail the device
probe even though there's nothing wrong.

Fix it by just polling the status register until we get the indication that
the device is up and running. As a side effect of this fix, requesting the
IRQ is also moved to after the setup function.

Fixes: f110f3188e563 ("iio: temperature: Add support for LTC2983")
Reported-and-tested-by: Drew Fustini <drew@pdp7.com>
Reviewed-by: Drew Fustini <drew@pdp7.com>
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: <Stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210811133220.190264-2-nuno.sa@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/iio/temperature/ltc2983.c | 30 ++++++++++++++----------------
1 file changed, 14 insertions(+), 16 deletions(-)

--- a/drivers/iio/temperature/ltc2983.c
+++ b/drivers/iio/temperature/ltc2983.c
@@ -89,6 +89,8 @@

#define LTC2983_STATUS_START_MASK BIT(7)
#define LTC2983_STATUS_START(x) FIELD_PREP(LTC2983_STATUS_START_MASK, x)
+#define LTC2983_STATUS_UP_MASK GENMASK(7, 6)
+#define LTC2983_STATUS_UP(reg) FIELD_GET(LTC2983_STATUS_UP_MASK, reg)

#define LTC2983_STATUS_CHAN_SEL_MASK GENMASK(4, 0)
#define LTC2983_STATUS_CHAN_SEL(x) \
@@ -1362,17 +1364,16 @@ put_child:

static int ltc2983_setup(struct ltc2983_data *st, bool assign_iio)
{
- u32 iio_chan_t = 0, iio_chan_v = 0, chan, iio_idx = 0;
+ u32 iio_chan_t = 0, iio_chan_v = 0, chan, iio_idx = 0, status;
int ret;
- unsigned long time;
-
- /* make sure the device is up */
- time = wait_for_completion_timeout(&st->completion,
- msecs_to_jiffies(250));

- if (!time) {
+ /* make sure the device is up: start bit (7) is 0 and done bit (6) is 1 */
+ ret = regmap_read_poll_timeout(st->regmap, LTC2983_STATUS_REG, status,
+ LTC2983_STATUS_UP(status) == 1, 25000,
+ 25000 * 10);
+ if (ret) {
dev_err(&st->spi->dev, "Device startup timed out\n");
- return -ETIMEDOUT;
+ return ret;
}

st->iio_chan = devm_kzalloc(&st->spi->dev,
@@ -1492,10 +1493,11 @@ static int ltc2983_probe(struct spi_devi
ret = ltc2983_parse_dt(st);
if (ret)
return ret;
- /*
- * let's request the irq now so it is used to sync the device
- * startup in ltc2983_setup()
- */
+
+ ret = ltc2983_setup(st, true);
+ if (ret)
+ return ret;
+
ret = devm_request_irq(&spi->dev, spi->irq, ltc2983_irq_handler,
IRQF_TRIGGER_RISING, name, st);
if (ret) {
@@ -1503,10 +1505,6 @@ static int ltc2983_probe(struct spi_devi
return ret;
}

- ret = ltc2983_setup(st, true);
- if (ret)
- return ret;
-
indio_dev->name = name;
indio_dev->num_channels = st->iio_channels;
indio_dev->channels = st->iio_chan;