On Sun, 15 Sep 2019 13:53:26 +0100 Jonathan Cameron <[email protected]> wrote:
> On Mon, 9 Sep 2019 14:37:21 +0200 > Andreas Klinger <[email protected]> wrote: > > > 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 <[email protected]> > > Applied to the fixes-togreg branch of iio.git and marked for stable. > > Thanks, I should have waited for my local tests to finish. This result in val being unused, so I've removed it. Thanks, Jonathan > > Jonathan > > > --- > > drivers/iio/adc/hx711.c | 9 +++++---- > > 1 file changed, 5 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/iio/adc/hx711.c b/drivers/iio/adc/hx711.c > > index 88c7fe15003b..0678964dbd21 100644 > > --- a/drivers/iio/adc/hx711.c > > +++ b/drivers/iio/adc/hx711.c > > @@ -101,13 +101,14 @@ 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 +118,6 @@ 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 +125,7 @@ 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 +133,8 @@ 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) >
