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gpioiic: never drive lines active high

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I2C communication is done by a combination of driving a line low or
letting it float, so that it is either pulled up or driven low by
another party.

r355276 besides the stated goal of the change -- using the new GPIO API
-- also changed the logic, so that active state is signaled by actively
driving a line.

That worked with iicbb prior to r362042, but stopped working after that
commit on at least some hardware.  My guess that the breakage was
related to getting an ACK bit.  A device expected to be able to drive
SDA actively low, but controller was actively driving it high for some
time.

Anyway, this change seems to fix the problem.
Tested using gpioiic on Orange Pi PC Plus with HTU21 sensor.

Reported by:	Nick Kostirya <nikolay.kostirya@i11.co>
Reviewed by:	manu
MFC after:	1 week
Differential Revision: https://reviews.freebsd.org/D25684
This commit is contained in:
Andriy Gapon 2020-07-21 07:35:03 +00:00
parent c4cbf1fbab
commit e57f9c8a9f
1 changed files with 14 additions and 11 deletions
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25
sys/dev/gpio/gpioiic.c
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@ -191,16 +191,14 @@ static void
gpioiic_setsda(device_t dev, int val)
{
struct gpioiic_softc *sc = device_get_softc(dev);
int err;
/*
* Some controllers cannot set an output value while a pin is in input
* mode; in that case we set the pin again after changing mode.
*/
err = gpio_pin_set_active(sc->sdapin, val);
gpio_pin_setflags(sc->sdapin, GPIO_PIN_OUTPUT | GPIO_PIN_OPENDRAIN);
if (err != 0)
gpio_pin_set_active(sc->sdapin, val);
if (val) {
gpio_pin_setflags(sc->sdapin, GPIO_PIN_INPUT);
} else {
gpio_pin_setflags(sc->sdapin,
GPIO_PIN_OUTPUT | GPIO_PIN_OPENDRAIN);
gpio_pin_set_active(sc->sdapin, 0);
}
}
static void
@ -208,8 +206,13 @@ gpioiic_setscl(device_t dev, int val)
{
struct gpioiic_softc *sc = device_get_softc(dev);
gpio_pin_setflags(sc->sclpin, GPIO_PIN_OUTPUT | GPIO_PIN_OPENDRAIN);
gpio_pin_set_active(sc->sclpin, val);
if (val) {
gpio_pin_setflags(sc->sclpin, GPIO_PIN_INPUT);
} else {
gpio_pin_setflags(sc->sclpin,
GPIO_PIN_OUTPUT | GPIO_PIN_OPENDRAIN);
gpio_pin_set_active(sc->sclpin, 0);
}
}
static int