The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 4043ecfb5fc4355a090111e14faf7945ff0fdbd5 Mon Sep 17 00:00:00 2001
From: Andreas Klinger <ak@xxxxxxxxxxxxx>
Date: Mon, 9 Sep 2019 14:37:21 +0200
Subject: [PATCH] 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@xxxxxxxxxxxxx>
Cc: <Stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
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)
