1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
31  * Generic I2C bit-banging code
42  * (c) 1998 Gerd Knorr <kraxel@cs.tu-berlin.de>
76 	u_int udelay;		/* signal toggle delay in usec */
137 	device_set_desc(dev, "I2C bit-banging driver");  in iicbb_probe()
147 	sc->iicbus = device_add_child(dev, "iicbus", DEVICE_UNIT_ANY);  in iicbb_attach()
148 	if (!sc->iicbus)  in iicbb_attach()
151 	sc->scl_low_timeout = DEFAULT_SCL_LOW_TIMEOUT;  in iicbb_attach()
155 	    "delay", CTLFLAG_RD, &sc->udelay,  in iicbb_attach()
156 	    0, "Signal change delay controlled by bus frequency, microseconds");  in iicbb_attach()
160 	    "scl_low_timeout", CTLFLAG_RWTUN, &sc->scl_low_timeout,  in iicbb_attach()
164 	    "io_latency", CTLFLAG_RWTUN, &sc->io_latency,  in iicbb_attach()
196 	if (child == sc->iicbus)  in iicbb_child_detached()
197 		sc->iicbus = NULL;  in iicbb_child_detached()
211 		retval += printf(" on %s master-only\n",  in iicbb_print_child()
230     &i2c_debug, 0, "Enable i2c bit-banging driver debug");
254 	timeout = now + sc->scl_low_timeout * SBT_1US;  in iicbb_waitforscl()
263 		pause_sbt("iicbb-scl-low", SBT_1MS, 0, C_PREL(2));  in iicbb_waitforscl()
281 	 * - set SDA to the value;  in iicbb_clockin()
282 	 * - release SCL and wait until it's high.  in iicbb_clockin()
285 	 * There should be a data set-up time, 250 ns minimum, between setting  in iicbb_clockin()
287 	 * naturally provide that delay.  in iicbb_clockin()
295  * End the high phase of the clock and wait out the low phase
306 	 * - pull SCL low and hold for udelay.  in iicbb_clockout()
309 	DELAY(sc->udelay);  in iicbb_clockout()
321 	DELAY(sc->udelay);  in iicbb_sendbit()
332  * Now it must wait for the SLAVE to pull the DATA line low.
355 	for (t = 0; t < sc->udelay; t++) {  in iicbb_getack()
359 		DELAY(1);  in iicbb_getack()
362 	DELAY(sc->udelay - t);  in iicbb_getack()
365 	I2C_DEBUG(printf("%c ", noack ? '-' : '+'));  in iicbb_getack()
374 	for (i = 7; i >= 0; i--) {  in iicbb_sendbyte()
398 	for (i = 7; i >= 0; i--) {  in iicbb_readbyte()
405 		DELAY((sc->udelay + 1) / 2);  in iicbb_readbyte()
408 		DELAY((sc->udelay + 1) / 2);  in iicbb_readbyte()
413 	 * Send master->slave ACK (low) for more data,  in iicbb_readbyte()
417 	I2C_DEBUG(printf("r%02x%c ", *data, last ? '-' : '+'));  in iicbb_readbyte()
455 		DELAY((sc->udelay + 1) / 2);  in iicbb_start_impl()
467 	/* Start: SDA high->low. */  in iicbb_start_impl()
470 	/* Wait the second half of the SCL high phase. */  in iicbb_start_impl()
471 	DELAY((sc->udelay + 1) / 2);  in iicbb_start_impl()
513 	DELAY((sc->udelay + 1) / 2);  in iicbb_stop()
515 	DELAY((sc->udelay + 1) / 2);  in iicbb_stop()
538 		len--;  in iicbb_write()
545 /* NB: whatever delay is, it's ignored. */
547 iicbb_read(device_t dev, char *buf, int len, int *read, int last, int delay)  in iicbb_read()  argument
559 		len--;  in iicbb_read()
590 	busfreq = IICBUS_GET_FREQUENCY(sc->iicbus, speed);  in iicbb_set_speed()
591 	period = 1000000 / 2 / busfreq;	/* Hz -> uS */  in iicbb_set_speed()
592 	period -= sc->io_latency;  in iicbb_set_speed()
593 	sc->udelay = MAX(period, 1);  in iicbb_set_speed()