| Message ID | 20190909123720.qdew2c4evxd6dpyk@arbad (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | iio: adc: hx711: fix and optimize sampling of data | expand |
On Mon, 9 Sep 2019 14:37:21 +0200 Andreas Klinger <ak@it-klinger.de> 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 <ak@it-klinger.de> Applied to the fixes-togreg branch of iio.git and marked for stable. Thanks, 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)
On Sun, 15 Sep 2019 13:53:26 +0100 Jonathan Cameron <jic23@kernel.org> wrote: > On Mon, 9 Sep 2019 14:37:21 +0200 > Andreas Klinger <ak@it-klinger.de> 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 <ak@it-klinger.de> > > 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) >
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)
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> --- drivers/iio/adc/hx711.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)