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| author | Andreas Klinger <ak@it-klinger.de> | 2019-09-09 14:37:21 +0200 |
|---|---|---|
| committer | Jonathan Cameron <Jonathan.Cameron@huawei.com> | 2019-10-09 19:11:25 +0100 |
| commit | 4043ecfb5fc4355a090111e14faf7945ff0fdbd5 (patch) | |
| tree | a98a336e51142e4dbb844fa9a5c6826af7e73028 | |
| parent | 6c59a962e081df6d8fe43325bbfabec57e0d4751 (diff) | |
| download | linux-stable-4043ecfb5fc4355a090111e14faf7945ff0fdbd5.tar.gz linux-stable-4043ecfb5fc4355a090111e14faf7945ff0fdbd5.tar.bz2 linux-stable-4043ecfb5fc4355a090111e14faf7945ff0fdbd5.zip | |
iio: adc: hx711: fix bug in sampling of data
Fix bug in sampling function hx711_cycle() when interrupt occures while
PD_SCK is high. If PD_SCK is high for at least 60 us power down mode of
the sensor is entered which in turn leads to a wrong measurement.
Switch off interrupts during a PD_SCK high period and move query of DOUT
to the latest point of time which is at the end of PD_SCK low period.
This bug exists in the driver since it's initial addition. The more
interrupts on the system the higher is the probability that it happens.
Fixes: c3b2fdd0ea7e ("iio: adc: hx711: Add IIO driver for AVIA HX711")
Signed-off-by: Andreas Klinger <ak@it-klinger.de>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
| -rw-r--r-- | drivers/iio/adc/hx711.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/drivers/iio/adc/hx711.c b/drivers/iio/adc/hx711.c index 88c7fe15003b..62e6c8badd22 100644 --- a/drivers/iio/adc/hx711.c +++ b/drivers/iio/adc/hx711.c @@ -100,14 +100,14 @@ struct hx711_data { static int hx711_cycle(struct hx711_data *hx711_data) { - int val; + unsigned long flags; /* * if preempted for more then 60us while PD_SCK is high: * hx711 is going in reset * ==> measuring is false */ - preempt_disable(); + local_irq_save(flags); gpiod_set_value(hx711_data->gpiod_pd_sck, 1); /* @@ -117,7 +117,6 @@ static int hx711_cycle(struct hx711_data *hx711_data) */ ndelay(hx711_data->data_ready_delay_ns); - val = gpiod_get_value(hx711_data->gpiod_dout); /* * here we are not waiting for 0.2 us as suggested by the datasheet, * because the oscilloscope showed in a test scenario @@ -125,7 +124,7 @@ static int hx711_cycle(struct hx711_data *hx711_data) * and 0.56 us for PD_SCK low on TI Sitara with 800 MHz */ gpiod_set_value(hx711_data->gpiod_pd_sck, 0); - preempt_enable(); + local_irq_restore(flags); /* * make it a square wave for addressing cases with capacitance on @@ -133,7 +132,8 @@ static int hx711_cycle(struct hx711_data *hx711_data) */ ndelay(hx711_data->data_ready_delay_ns); - return val; + /* sample as late as possible */ + return gpiod_get_value(hx711_data->gpiod_dout); } static int hx711_read(struct hx711_data *hx711_data) |