Add sxitwi(4), a driver for the (i2c compatible) two-wire bus found on

several Allwinner SoCs.  From Artturi Alm, based on code from NetBSD.

Also add axppmic(4), a driver for the AXP209 i2c PMIC, which provides
power down support.  Written by Artturi Alm.

5 files changed, 634 insertions, 3 deletions

diff --git a/sys/arch/armv7/conf/GENERIC b/sys/arch/armv7/conf/GENERIC
index af71a6c4835..8b10acdb114 100644
--- a/sys/arch/armv7/conf/GENERIC
+++ b/sys/arch/armv7/conf/GENERIC
@@ -1,4 +1,4 @@
-#	$OpenBSD: GENERIC,v 1.83 2017/05/21 17:44:52 kettenis Exp $
+#	$OpenBSD: GENERIC,v 1.84 2017/07/23 19:26:03 kettenis Exp $
 #
 # For further information on compiling OpenBSD kernels, see the config(8)
 # man page.
@@ -99,6 +99,8 @@ ehci*		at fdt?			# EHCI (shim)
 usb*		at ehci?	#flags 0x1
 #ohci*		at sunxi?
 #usb*		at ohci?
+sxitwi*		at fdt?			# Two-Wire Serial Interface
+iic*		at sxitwi?		# I2C bus
 
 # ARM Versatile Express
 sysreg*		at fdt?
@@ -148,6 +150,7 @@ mvxhci*		at fdt?
 usb*		at mvxhci?
 mvahci*		at fdt?
 
+axppmic*	at iic?			# axp209 pmic
 crosec*		at iic?
 wskbd*		at crosec? mux 1
 pcfrtc*		at iic?
diff --git a/sys/arch/armv7/conf/RAMDISK b/sys/arch/armv7/conf/RAMDISK
index 56e64893df6..59a5709cf72 100644
--- a/sys/arch/armv7/conf/RAMDISK
+++ b/sys/arch/armv7/conf/RAMDISK
@@ -1,4 +1,4 @@
-#	$OpenBSD: RAMDISK,v 1.79 2017/07/05 14:58:59 visa Exp $
+#	$OpenBSD: RAMDISK,v 1.80 2017/07/23 19:26:03 kettenis Exp $
 
 machine		armv7 arm
 
@@ -99,6 +99,8 @@ ehci*		at fdt?			# EHCI (shim)
 usb*		at ehci?	#flags 0x1
 #ohci*		at sunxi?
 #usb*		at ohci?
+sxitwi*		at fdt?			# Two-Wire Serial Interface
+iic*		at sxitwi?		# I2C bus
 
 # ARM Versatile Express
 sysreg*		at fdt?
@@ -145,6 +147,7 @@ mvxhci*		at fdt?
 usb*		at mvxhci?
 mvahci*		at fdt?
 
+axppmic*	at iic?			# axp209 pmic
 crosec*		at iic?
 wskbd*		at crosec? mux 1
 pcfrtc*		at iic?
diff --git a/sys/dev/fdt/axp20x.c b/sys/dev/fdt/axp20x.c
new file mode 100644
index 00000000000..f09f38c97a3
--- /dev/null
+++ b/sys/dev/fdt/axp20x.c
@@ -0,0 +1,135 @@
+/* $OpenBSD: axp20x.c,v 1.1 2017/07/23 19:26:03 kettenis Exp $ */
+/*
+ * Copyright (c) 2014,2016 Artturi Alm
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/device.h>
+#include <sys/sensors.h>
+
+#include <dev/i2c/i2cvar.h>
+
+#include <machine/bus.h>
+#include <machine/fdt.h>
+
+#include <dev/ofw/openfirm.h>
+#include <dev/ofw/fdt.h>
+
+#include <armv7/armv7/armv7_machdep.h>	/* needed for powerdownfn */
+
+/* Power Status Register / Input power status */
+#define	AXP209_PSR		0x00
+#define	AXP209_PSR_ACIN		(1 << 7)	/* ACIN Exists */
+#define	AXP209_PSR_VBUS		(1 << 5)	/* VBUS Exists */
+
+/* Shutdown settings, battery detection, and CHGLED Pin control */
+#define	AXP209_SDR		0x32
+#define	AXP209_SDR_SHUTDOWN	(1 << 7)	/* Shutdown Control */
+
+struct axp20x_softc {
+	struct device	sc_dev;
+	i2c_tag_t	sc_i2c;
+	i2c_addr_t	sc_addr;
+};
+
+int	axp20x_match(struct device *, void *, void *);
+void	axp20x_attach(struct device *, struct device *, void *);
+
+int	axp20x_readb(uint8_t, uint8_t *);
+int	axp20x_writeb(uint8_t, uint8_t);
+void	axp20x_shutdown(void);
+
+struct cfattach axppmic_ca = {
+	sizeof(struct axp20x_softc), axp20x_match, axp20x_attach
+};
+
+struct cfdriver axppmic_cd = {
+	NULL, "axppmic", DV_DULL
+};
+
+int
+axp20x_match(struct device *parent, void *match, void *aux)
+{
+	struct i2c_attach_args *ia = aux;
+	int node = *(int *)ia->ia_cookie;
+
+	return OF_is_compatible(node, "x-powers,axp209");
+}
+
+void
+axp20x_attach(struct device *parent, struct device *self, void *aux)
+{
+	struct axp20x_softc *sc = (struct axp20x_softc *)self;
+	struct i2c_attach_args *ia = aux;
+	uint8_t psr;
+
+	sc->sc_i2c = ia->ia_tag;
+	sc->sc_addr = ia->ia_addr;
+
+	axp20x_readb(AXP209_PSR, &psr);
+	printf(": AXP209,");
+	if ((psr & (AXP209_PSR_ACIN | AXP209_PSR_VBUS)) == 0)
+		printf(" BAT");
+	else {
+		if (psr & AXP209_PSR_ACIN)
+			printf(" ACIN");
+		if (psr & AXP209_PSR_VBUS)
+			printf(" VBUS");
+	}
+	printf("\n");
+
+	powerdownfn = axp20x_shutdown;
+}
+
+int
+axp20x_readb(uint8_t reg, uint8_t *val)
+{
+	struct axp20x_softc *sc = axppmic_cd.cd_devs[0];
+	int flags = I2C_F_POLL;
+	int ret;
+
+	if (sc == NULL)
+		return ENXIO;
+
+	iic_acquire_bus(sc->sc_i2c, flags);
+	ret = iic_smbus_read_byte(sc->sc_i2c, sc->sc_addr, reg, val, flags);
+	iic_release_bus(sc->sc_i2c, flags);
+	return ret;
+
+}
+
+int
+axp20x_writeb(uint8_t reg, uint8_t data)
+{
+	struct axp20x_softc *sc = axppmic_cd.cd_devs[0];
+	int flags = I2C_F_POLL;
+	int ret;
+
+	if (sc == NULL)
+		return ENXIO;
+
+	iic_acquire_bus(sc->sc_i2c, flags);
+	ret = iic_smbus_write_byte(sc->sc_i2c, sc->sc_addr, reg, data, flags);
+	iic_release_bus(sc->sc_i2c, flags);
+
+	return ret;
+}
+
+void
+axp20x_shutdown(void)
+{
+	axp20x_writeb(AXP209_SDR, AXP209_SDR_SHUTDOWN);
+}
diff --git a/sys/dev/fdt/files.fdt b/sys/dev/fdt/files.fdt
index 9e2f64cbdaa..d55a22de1f9 100644
--- a/sys/dev/fdt/files.fdt
+++ b/sys/dev/fdt/files.fdt
@@ -1,4 +1,4 @@
-#	$OpenBSD: files.fdt,v 1.17 2017/05/21 08:59:45 kettenis Exp $
+#	$OpenBSD: files.fdt,v 1.18 2017/07/23 19:26:03 kettenis Exp $
 #
 # Config file and device description for machine-independent FDT code.
 # Included by ports that need it.
@@ -23,6 +23,14 @@ device	sximmc: sdmmcbus
 attach	sximmc at fdt
 file	dev/fdt/sximmc.c		sximmc
 
+device	sxitwi: i2cbus
+attach	sxitwi at fdt
+file	dev/fdt/sxitwi.c		sxitwi
+
+device	axppmic
+attach	axppmic at i2c
+file	dev/fdt/axp20x.c		axppmic
+
 device	bcmdog
 attach	bcmdog at fdt
 file	dev/fdt/bcm2835_dog.c		bcmdog
diff --git a/sys/dev/fdt/sxitwi.c b/sys/dev/fdt/sxitwi.c
new file mode 100644
index 00000000000..260f6f1de57
--- /dev/null
+++ b/sys/dev/fdt/sxitwi.c
@@ -0,0 +1,482 @@
+/* $OpenBSD: sxitwi.c,v 1.1 2017/07/23 19:26:03 kettenis Exp $ */
+/*	$NetBSD: gttwsi_core.c,v 1.2 2014/11/23 13:37:27 jmcneill Exp $	*/
+/*
+ * Copyright (c) 2008 Eiji Kawauchi.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *      This product includes software developed for the NetBSD Project by
+ *      Eiji Kawauchi.
+ * 4. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+/*
+ * Copyright (c) 2005 Brocade Communcations, inc.
+ * All rights reserved.
+ *
+ * Written by Matt Thomas for Brocade Communcations, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of Brocade Communications, Inc. may not be used to endorse
+ *    or promote products derived from this software without specific prior
+ *    written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY BROCADE COMMUNICATIONS, INC. ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL EITHER BROCADE COMMUNICATIONS, INC. BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * Marvell Two-Wire Serial Interface (aka I2C) master driver
+ */
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/device.h>
+#include <sys/kernel.h>
+#include <sys/rwlock.h>
+
+#include <sys/param.h>
+#include <sys/device.h>
+#include <sys/systm.h>
+
+#define	_I2C_PRIVATE
+#include <dev/i2c/i2cvar.h>
+
+#include <machine/bus.h>
+#include <machine/fdt.h>
+
+#include <dev/ofw/openfirm.h>
+#include <dev/ofw/ofw_clock.h>
+#include <dev/ofw/ofw_pinctrl.h>
+#include <dev/ofw/fdt.h>
+
+#define	TWI_CCR_REG		0x14
+#define	TWI_CCR_CLK_M		(0x0f << 3)
+#define	TWI_CCR_CLK_N		(0x07 << 0)
+
+#define	TWSI_SLAVEADDR		0x00
+#define	TWSI_EXTEND_SLAVEADDR	0x04
+#define	TWSI_DATA		0x08
+#define	TWSI_CONTROL		0x0c
+#define	TWSI_STATUS		0x10
+#define	TWSI_BAUDRATE		0x14
+#define	TWSI_SOFTRESET		0x18
+
+#define	SLAVEADDR_GCE_MASK	0x01
+#define	SLAVEADDR_SADDR_MASK	0xfe
+
+#define	EXTEND_SLAVEADDR_MASK	0xff
+
+#define	DATA_MASK		0xff
+
+#define	CONTROL_ACK		(1 << 2)
+#define	CONTROL_IFLG		(1 << 3)
+#define	CONTROL_STOP		(1 << 4)
+#define	CONTROL_START		(1 << 5)
+#define	CONTROL_TWSIEN		(1 << 6)
+#define	CONTROL_INTEN		(1 << 7)
+
+#define	STAT_BE		0x00	/* Bus Error */
+#define	STAT_SCT	0x08	/* Start condition transmitted */
+#define	STAT_RSCT	0x10	/* Repeated start condition transmitted */
+#define	STAT_AWBT_AR	0x18	/* Address + write bit transd, ack recvd */
+#define	STAT_AWBT_ANR	0x20	/* Address + write bit transd, ack not recvd */
+#define	STAT_MTDB_AR	0x28	/* Master transd data byte, ack recvd */
+#define	STAT_MTDB_ANR	0x30	/* Master transd data byte, ack not recvd */
+#define	STAT_MLADADT	0x38	/* Master lost arbitr during addr or data tx */
+#define	STAT_ARBT_AR	0x40	/* Address + read bit transd, ack recvd */
+#define	STAT_ARBT_ANR	0x48	/* Address + read bit transd, ack not recvd */
+#define	STAT_MRRD_AT	0x50	/* Master received read data, ack transd */
+#define	STAT_MRRD_ANT	0x58	/* Master received read data, ack not transd */
+#define	STAT_SAWBT_AR	0xd0	/* Second addr + write bit transd, ack recvd */
+#define	STAT_SAWBT_ANR	0xd8	/* S addr + write bit transd, ack not recvd */
+#define	STAT_SARBT_AR	0xe0	/* Second addr + read bit transd, ack recvd */
+#define	STAT_SARBT_ANR	0xe8	/* S addr + read bit transd, ack not recvd */
+#define	STAT_NRS	0xf8	/* No relevant status */
+
+#define	SOFTRESET_VAL		0		/* reset value */
+
+#define	TWSI_RETRY_COUNT	1000		/* retry loop count */
+#define	TWSI_RETRY_DELAY	1		/* retry delay */
+#define	TWSI_STAT_DELAY		1		/* poll status delay */
+#define	TWSI_READ_DELAY		2		/* read delay */
+#define	TWSI_WRITE_DELAY	2		/* write delay */
+
+struct sxitwi_softc {
+	struct device		 sc_dev;
+	bus_space_tag_t		 sc_iot;
+	bus_space_handle_t	 sc_ioh;
+	int			 sc_node;
+	u_int			 sc_started;
+	struct i2c_controller	 sc_ic;
+	struct rwlock		 sc_buslock;
+	void			*sc_ih;
+};
+
+void	sxitwi_attach(struct device *, struct device *, void *);
+int	sxitwi_match(struct device *, void *, void *);
+void	sxitwi_bus_scan(struct device *, struct i2cbus_attach_args *, void *);
+
+int	sxitwi_intr(void *);
+int	sxitwi_acquire_bus(void *, int);
+void	sxitwi_release_bus(void *, int);
+int	sxitwi_send_start(void *, int);
+int	sxitwi_send_stop(void *, int);
+int	sxitwi_initiate_xfer(void *, i2c_addr_t, int);
+int	sxitwi_read_byte(void *, uint8_t *, int);
+int	sxitwi_write_byte(void *, uint8_t, int);
+int	sxitwi_wait(struct sxitwi_softc *, u_int, u_int, int);
+static inline u_int sxitwi_read_4(struct sxitwi_softc *, u_int);
+static inline void sxitwi_write_4(struct sxitwi_softc *, u_int, u_int);
+
+struct cfdriver sxitwi_cd = {
+	NULL, "sxitwi", DV_DULL
+};
+
+struct cfattach sxitwi_ca = {
+	sizeof(struct sxitwi_softc), sxitwi_match, sxitwi_attach
+};
+
+int
+sxitwi_match(struct device *parent, void *match, void *aux)
+{
+	struct fdt_attach_args *faa = aux;
+
+	return (OF_is_compatible(faa->fa_node, "allwinner,sun4i-a10-i2c") |
+	    OF_is_compatible(faa->fa_node, "allwinner,sun7i-a20-i2c"));
+}
+
+void
+sxitwi_attach(struct device *parent, struct device *self, void *aux)
+{
+	struct sxitwi_softc *sc = (struct sxitwi_softc *)self;
+	struct fdt_attach_args *faa = aux;
+	struct i2cbus_attach_args iba;
+
+	if (faa->fa_nreg < 1) {
+		printf(": no registers\n");
+		return;
+	}
+
+	sc->sc_node = faa->fa_node;
+	sc->sc_iot = faa->fa_iot;
+
+	if (bus_space_map(sc->sc_iot, faa->fa_reg[0].addr,
+	    faa->fa_reg[0].size, 0, &sc->sc_ioh)) {
+		printf(": can't map registers\n");
+		return;
+	}
+
+	rw_init(&sc->sc_buslock, sc->sc_dev.dv_xname);
+
+	sc->sc_started = 0;
+	sc->sc_ic.ic_cookie = sc;
+	sc->sc_ic.ic_acquire_bus = sxitwi_acquire_bus;
+	sc->sc_ic.ic_release_bus = sxitwi_release_bus;
+	sc->sc_ic.ic_exec = NULL;
+	sc->sc_ic.ic_send_start = sxitwi_send_start;
+	sc->sc_ic.ic_send_stop = sxitwi_send_stop;
+	sc->sc_ic.ic_initiate_xfer = sxitwi_initiate_xfer;
+	sc->sc_ic.ic_read_byte = sxitwi_read_byte;
+	sc->sc_ic.ic_write_byte = sxitwi_write_byte;
+
+	pinctrl_byname(faa->fa_node, "default");
+
+	/* Enable clock */
+	clock_enable(faa->fa_node, NULL);
+
+	/*
+	 * Set clock rate to 100kHz. From the datasheet:
+	 *   For 100Khz standard speed 2Wire, CLK_N=2, CLK_M=11
+	 *   F0=48M/2^2=12Mhz, F1=F0/(10*(11+1)) = 0.1Mhz
+	 */
+	sxitwi_write_4(sc, TWI_CCR_REG, (11 << 3) | (2 << 0));
+
+	/* Put the controller into Soft Reset. */
+	sxitwi_write_4(sc, TWSI_SOFTRESET, SOFTRESET_VAL);
+
+	/* Establish interrupt */
+	sc->sc_ih = arm_intr_establish_fdt(faa->fa_node, IPL_BIO,
+	    sxitwi_intr, sc, sc->sc_dev.dv_xname);
+	if (sc->sc_ih == NULL) {
+		printf(": can't to establish interrupt\n");
+		return;
+	}
+
+	printf("\n");
+
+	/* Configure its children */
+	memset(&iba, 0, sizeof(iba));
+	iba.iba_name = "iic";
+	iba.iba_tag = &sc->sc_ic;
+	iba.iba_bus_scan = sxitwi_bus_scan;
+	iba.iba_bus_scan_arg = &sc->sc_node;
+
+	config_found(&sc->sc_dev, &iba, iicbus_print);
+}
+
+void
+sxitwi_bus_scan(struct device *self, struct i2cbus_attach_args *iba, void *arg)
+{
+	int iba_node = *(int *)arg;
+	struct i2c_attach_args ia;
+	char name[32];
+	uint32_t reg[1];
+	int node;
+
+	for (node = OF_child(iba_node); node; node = OF_peer(node)) {
+		memset(name, 0, sizeof(name));
+		memset(reg, 0, sizeof(reg));
+
+		if (OF_getprop(node, "compatible", name, sizeof(name)) == -1)
+			continue;
+		if (name[0] == '\0')
+			continue;
+
+		if (OF_getprop(node, "reg", &reg, sizeof(reg)) != sizeof(reg))
+			continue;
+
+		memset(&ia, 0, sizeof(ia));
+		ia.ia_tag = iba->iba_tag;
+		ia.ia_addr = bemtoh32(&reg[0]);
+		ia.ia_name = name;
+		ia.ia_cookie = &node;
+		config_found(self, &ia, iic_print);
+	}
+}
+
+u_int
+sxitwi_read_4(struct sxitwi_softc *sc, u_int reg)
+{
+	u_int val = bus_space_read_4(sc->sc_iot, sc->sc_ioh, reg);
+
+	delay(TWSI_READ_DELAY);
+
+	return val;
+}
+
+void
+sxitwi_write_4(struct sxitwi_softc *sc, u_int reg, u_int val)
+{
+	bus_space_write_4(sc->sc_iot, sc->sc_ioh, reg, val);
+
+	delay(TWSI_WRITE_DELAY);
+
+	return;
+}
+
+int
+sxitwi_intr(void *arg)
+{
+	struct sxitwi_softc *sc = arg;
+	u_int val;
+
+	val = sxitwi_read_4(sc, TWSI_CONTROL);
+	if (val & CONTROL_IFLG) {
+		sxitwi_write_4(sc, TWSI_CONTROL, val & ~CONTROL_INTEN);
+		wakeup(&sc->sc_dev);
+		return 1;
+	}
+	return 0;
+}
+
+int
+sxitwi_acquire_bus(void *arg, int flags)
+{
+	struct sxitwi_softc *sc = arg;
+
+	if (flags & I2C_F_POLL)
+		return 0;
+
+	return rw_enter(&sc->sc_buslock, RW_WRITE);
+}
+
+void
+sxitwi_release_bus(void *arg, int flags)
+{
+	struct sxitwi_softc *sc = arg;
+
+	if (flags & I2C_F_POLL)
+		return;
+
+	rw_exit(&sc->sc_buslock);
+}
+
+int
+sxitwi_send_start(void *v, int flags)
+{
+	struct sxitwi_softc *sc = v;
+	int expect;
+
+	if (sc->sc_started)
+		expect = STAT_RSCT;
+	else
+		expect = STAT_SCT;
+	sc->sc_started = 1;
+
+	return sxitwi_wait(sc, CONTROL_START, expect, flags);
+}
+
+int
+sxitwi_send_stop(void *v, int flags)
+{
+	struct sxitwi_softc *sc = v;
+	int retry = TWSI_RETRY_COUNT;
+	u_int control;
+
+	sc->sc_started = 0;
+
+	/* Interrupt is not generated for STAT_NRS. */
+	control = CONTROL_STOP | CONTROL_TWSIEN;
+	sxitwi_write_4(sc, TWSI_CONTROL, control);
+	while (--retry > 0) {
+		if (sxitwi_read_4(sc, TWSI_STATUS) == STAT_NRS)
+			return 0;
+		delay(TWSI_STAT_DELAY);
+	}
+
+	return -1;
+}
+
+int
+sxitwi_initiate_xfer(void *v, i2c_addr_t addr, int flags)
+{
+	struct sxitwi_softc *sc = v;
+	u_int data, expect;
+	int error, read;
+
+	sxitwi_send_start(v, flags);
+
+	read = (flags & I2C_F_READ) != 0;
+	if (read)
+		expect = STAT_ARBT_AR;
+	else
+		expect = STAT_AWBT_AR;
+
+	/*
+	 * First byte contains whether this xfer is a read or write.
+	 */
+	data = read;
+	if (addr > 0x7f) {
+		/*
+		 * If this is a 10bit request, the first address byte is
+		 * 0b11110<b9><b8><r/w>.
+		 */
+		data |= 0xf0 | ((addr & 0x300) >> 7);
+		sxitwi_write_4(sc, TWSI_DATA, data);
+		error = sxitwi_wait(sc, 0, expect, flags);
+		if (error)
+			return error;
+		/*
+		 * The first address byte has been sent, now to send
+		 * the second one.
+		 */
+		if (read)
+			expect = STAT_SARBT_AR;
+		else
+			expect = STAT_SAWBT_AR;
+		data = (uint8_t)addr;
+	} else
+		data |= (addr << 1);
+
+	sxitwi_write_4(sc, TWSI_DATA, data);
+	return sxitwi_wait(sc, 0, expect, flags);
+}
+
+int
+sxitwi_read_byte(void *v, uint8_t *valp, int flags)
+{
+	struct sxitwi_softc *sc = v;
+	int error;
+
+	if (flags & I2C_F_LAST)
+		error = sxitwi_wait(sc, 0, STAT_MRRD_ANT, flags);
+	else
+		error = sxitwi_wait(sc, CONTROL_ACK, STAT_MRRD_AT, flags);
+	if (!error)
+		*valp = sxitwi_read_4(sc, TWSI_DATA);
+	if ((flags & (I2C_F_LAST | I2C_F_STOP)) == (I2C_F_LAST | I2C_F_STOP))
+		error = sxitwi_send_stop(sc, flags);
+	return error;
+}
+
+int
+sxitwi_write_byte(void *v, uint8_t val, int flags)
+{
+	struct sxitwi_softc *sc = v;
+	int error;
+
+	sxitwi_write_4(sc, TWSI_DATA, val);
+	error = sxitwi_wait(sc, 0, STAT_MTDB_AR, flags);
+	if (flags & I2C_F_STOP)
+		sxitwi_send_stop(sc, flags);
+	return error;
+}
+
+int
+sxitwi_wait(struct sxitwi_softc *sc, u_int control, u_int expect, int flags)
+{
+	u_int status;
+	int timo, error = 0;
+
+	delay(5);
+	if (!(flags & I2C_F_POLL))
+		control |= CONTROL_INTEN;
+	sxitwi_write_4(sc, TWSI_CONTROL, control | CONTROL_TWSIEN);
+
+	timo = 0;
+	do {
+		control = sxitwi_read_4(sc, TWSI_CONTROL);
+		if (control & CONTROL_IFLG)
+			break;
+		if (flags & I2C_F_POLL)
+			delay(TWSI_RETRY_DELAY);
+		else {
+			error = tsleep(&sc->sc_dev, PWAIT, "sxitwi", 100);
+			if (error)
+				return error;
+		}
+	} while (++timo < 1000000);
+
+	status = sxitwi_read_4(sc, TWSI_STATUS);
+	if (status != expect)
+		return EIO;
+
+	return error;
+}