This is a note to let you know that I've just added the patch titled
iio: adc: hx711: fix bug in sampling of data
to my staging git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git in the staging-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 4043ecfb5fc4355a090111e14faf7945ff0fdbd5 Mon Sep 17 00:00:00 2001
From: Andreas Klinger ak@it-klinger.de Date: Mon, 9 Sep 2019 14:37:21 +0200 Subject: 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 --- drivers/iio/adc/hx711.c | 10 +++++----- 1 file 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)