svn commit: r363382 - head/sys/dev/gpio

[Andriy Gapon]

Author: avg
Date: Tue Jul 21 07:35:03 2020
New Revision: 363382
URL: https://svnweb.freebsd.org/changeset/base/363382

Log:
  gpioiic: never drive lines active high
  
  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 at i11.co>
  Reviewed by:	manu
  MFC after:	1 week
  Differential Revision: https://reviews.freebsd.org/D25684

Modified:
  head/sys/dev/gpio/gpioiic.c

Modified: head/sys/dev/gpio/gpioiic.c
==============================================================================
--- head/sys/dev/gpio/gpioiic.c	Mon Jul 20 23:57:53 2020	(r363381)
+++ head/sys/dev/gpio/gpioiic.c	Tue Jul 21 07:35:03 2020	(r363382)
@@ -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