patch "iio: adc: hx711: fix bug in sampling of data" added to staging-linus
Subsystems (3)
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 <[email protected]>
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.
--- drivers/iio/adc/hx711.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
drivers/iio/adc/hx711.c +5 -5
@@ -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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2.23.0