iio: adc: hx711: fix bug in sampling of data (4043ecfb) · Commits · 戴 / test

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: ("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

+5 −5

Original line number	Diff line number	Diff line
		@@ -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)

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