xref: /openbmc/linux/drivers/infiniband/hw/qib/qib_twsi.c (revision 04dccf5d)

/*
 * Copyright (c) 2012 Intel Corporation. All rights reserved.
 * Copyright (c) 2006 - 2012 QLogic Corporation. All rights reserved.
 * Copyright (c) 2003, 2004, 2005, 2006 PathScale, Inc. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - 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.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <linux/delay.h>
#include <linux/pci.h>
#include <linux/vmalloc.h>

#include "qib.h"

/*
 * QLogic_IB "Two Wire Serial Interface" driver.
 * Originally written for a not-quite-i2c serial eeprom, which is
 * still used on some supported boards. Later boards have added a
 * variety of other uses, most board-specific, so the bit-boffing
 * part has been split off to this file, while the other parts
 * have been moved to chip-specific files.
 *
 * We have also dropped all pretense of fully generic (e.g. pretend
 * we don't know whether '1' is the higher voltage) interface, as
 * the restrictions of the generic i2c interface (e.g. no access from
 * driver itself) make it unsuitable for this use.
 */

#define READ_CMD 1
#define WRITE_CMD 0

/**
 * i2c_wait_for_writes - wait for a write
 * @dd: the qlogic_ib device
 *
 * We use this instead of udelay directly, so we can make sure
 * that previous register writes have been flushed all the way
 * to the chip.  Since we are delaying anyway, the cost doesn't
 * hurt, and makes the bit twiddling more regular
 */
static void i2c_wait_for_writes(struct qib_devdata *dd)
{
	/*
	 * implicit read of EXTStatus is as good as explicit
	 * read of scratch, if all we want to do is flush
	 * writes.
	 */
	dd->f_gpio_mod(dd, 0, 0, 0);
	rmb(); /* inlined, so prevent compiler reordering */
}

/*
 * QSFP modules are allowed to hold SCL low for 500uSec. Allow twice that
 * for "almost compliant" modules
 */
#define SCL_WAIT_USEC 1000

/* BUF_WAIT is time bus must be free between STOP or ACK and to next START.
 * Should be 20, but some chips need more.
 */
#define TWSI_BUF_WAIT_USEC 60

static void scl_out(struct qib_devdata *dd, u8 bit)
{
	u32 mask;

	udelay(1);

	mask = 1UL << dd->gpio_scl_num;

	/* SCL is meant to be bare-drain, so never set "OUT", just DIR */
	dd->f_gpio_mod(dd, 0, bit ? 0 : mask, mask);

	/*
	 * Allow for slow slaves by simple
	 * delay for falling edge, sampling on rise.
	 */
	if (!bit)
		udelay(2);
	else {
		int rise_usec;

		for (rise_usec = SCL_WAIT_USEC; rise_usec > 0; rise_usec -= 2) {
			if (mask & dd->f_gpio_mod(dd, 0, 0, 0))
				break;
			udelay(2);
		}
		if (rise_usec <= 0)
			qib_dev_err(dd, "SCL interface stuck low > %d uSec\n",
				    SCL_WAIT_USEC);
	}
	i2c_wait_for_writes(dd);
}

static void sda_out(struct qib_devdata *dd, u8 bit)
{
	u32 mask;

	mask = 1UL << dd->gpio_sda_num;

	/* SDA is meant to be bare-drain, so never set "OUT", just DIR */
	dd->f_gpio_mod(dd, 0, bit ? 0 : mask, mask);

	i2c_wait_for_writes(dd);
	udelay(2);
}

static u8 sda_in(struct qib_devdata *dd, int wait)
{
	int bnum;
	u32 read_val, mask;

	bnum = dd->gpio_sda_num;
	mask = (1UL << bnum);
	/* SDA is meant to be bare-drain, so never set "OUT", just DIR */
	dd->f_gpio_mod(dd, 0, 0, mask);
	read_val = dd->f_gpio_mod(dd, 0, 0, 0);
	if (wait)
		i2c_wait_for_writes(dd);
	return (read_val & mask) >> bnum;
}

/**
 * i2c_ackrcv - see if ack following write is true
 * @dd: the qlogic_ib device
 */
static int i2c_ackrcv(struct qib_devdata *dd)
{
	u8 ack_received;

	/* AT ENTRY SCL = LOW */
	/* change direction, ignore data */
	ack_received = sda_in(dd, 1);
	scl_out(dd, 1);
	ack_received = sda_in(dd, 1) == 0;
	scl_out(dd, 0);
	return ack_received;
}

static void stop_cmd(struct qib_devdata *dd);

/**
 * rd_byte - read a byte, sending STOP on last, else ACK
 * @dd: the qlogic_ib device
 * @last: identifies the last read
 *
 * Returns byte shifted out of device
 */
static int rd_byte(struct qib_devdata *dd, int last)
{
	int bit_cntr, data;

	data = 0;

	for (bit_cntr = 7; bit_cntr >= 0; --bit_cntr) {
		data <<= 1;
		scl_out(dd, 1);
		data |= sda_in(dd, 0);
		scl_out(dd, 0);
	}
	if (last) {
		scl_out(dd, 1);
		stop_cmd(dd);
	} else {
		sda_out(dd, 0);
		scl_out(dd, 1);
		scl_out(dd, 0);
		sda_out(dd, 1);
	}
	return data;
}

/**
 * wr_byte - write a byte, one bit at a time
 * @dd: the qlogic_ib device
 * @data: the byte to write
 *
 * Returns 0 if we got the following ack, otherwise 1
 */
static int wr_byte(struct qib_devdata *dd, u8 data)
{
	int bit_cntr;
	u8 bit;

	for (bit_cntr = 7; bit_cntr >= 0; bit_cntr--) {
		bit = (data >> bit_cntr) & 1;
		sda_out(dd, bit);
		scl_out(dd, 1);
		scl_out(dd, 0);
	}
	return (!i2c_ackrcv(dd)) ? 1 : 0;
}

/*
 * issue TWSI start sequence:
 * (both clock/data high, clock high, data low while clock is high)
 */
static void start_seq(struct qib_devdata *dd)
{
	sda_out(dd, 1);
	scl_out(dd, 1);
	sda_out(dd, 0);
	udelay(1);
	scl_out(dd, 0);
}

/**
 * stop_seq - transmit the stop sequence
 * @dd: the qlogic_ib device
 *
 * (both clock/data low, clock high, data high while clock is high)
 */
static void stop_seq(struct qib_devdata *dd)
{
	scl_out(dd, 0);
	sda_out(dd, 0);
	scl_out(dd, 1);
	sda_out(dd, 1);
}

/**
 * stop_cmd - transmit the stop condition
 * @dd: the qlogic_ib device
 *
 * (both clock/data low, clock high, data high while clock is high)
 */
static void stop_cmd(struct qib_devdata *dd)
{
	stop_seq(dd);
	udelay(TWSI_BUF_WAIT_USEC);
}

/**
 * qib_twsi_reset - reset I2C communication
 * @dd: the qlogic_ib device
 */

int qib_twsi_reset(struct qib_devdata *dd)
{
	int clock_cycles_left = 9;
	int was_high = 0;
	u32 pins, mask;

	/* Both SCL and SDA should be high. If not, there
	 * is something wrong.
	 */
	mask = (1UL << dd->gpio_scl_num) | (1UL << dd->gpio_sda_num);

	/*
	 * Force pins to desired innocuous state.
	 * This is the default power-on state with out=0 and dir=0,
	 * So tri-stated and should be floating high (barring HW problems)
	 */
	dd->f_gpio_mod(dd, 0, 0, mask);

	/*
	 * Clock nine times to get all listeners into a sane state.
	 * If SDA does not go high at any point, we are wedged.
	 * One vendor recommends then issuing START followed by STOP.
	 * we cannot use our "normal" functions to do that, because
	 * if SCL drops between them, another vendor's part will
	 * wedge, dropping SDA and keeping it low forever, at the end of
	 * the next transaction (even if it was not the device addressed).
	 * So our START and STOP take place with SCL held high.
	 */
	while (clock_cycles_left--) {
		scl_out(dd, 0);
		scl_out(dd, 1);
		/* Note if SDA is high, but keep clocking to sync slave */
		was_high |= sda_in(dd, 0);
	}

	if (was_high) {
		/*
		 * We saw a high, which we hope means the slave is sync'd.
		 * Issue START, STOP, pause for T_BUF.
		 */

		pins = dd->f_gpio_mod(dd, 0, 0, 0);
		if ((pins & mask) != mask)
			qib_dev_err(dd, "GPIO pins not at rest: %d\n",
				    pins & mask);
		/* Drop SDA to issue START */
		udelay(1); /* Guarantee .6 uSec setup */
		sda_out(dd, 0);
		udelay(1); /* Guarantee .6 uSec hold */
		/* At this point, SCL is high, SDA low. Raise SDA for STOP */
		sda_out(dd, 1);
		udelay(TWSI_BUF_WAIT_USEC);
	}

	return !was_high;
}

#define QIB_TWSI_START 0x100
#define QIB_TWSI_STOP 0x200

/* Write byte to TWSI, optionally prefixed with START or suffixed with
 * STOP.
 * returns 0 if OK (ACK received), else != 0
 */
static int qib_twsi_wr(struct qib_devdata *dd, int data, int flags)
{
	int ret = 1;

	if (flags & QIB_TWSI_START)
		start_seq(dd);

	ret = wr_byte(dd, data); /* Leaves SCL low (from i2c_ackrcv()) */

	if (flags & QIB_TWSI_STOP)
		stop_cmd(dd);
	return ret;
}

/* Added functionality for IBA7220-based cards */
#define QIB_TEMP_DEV 0x98

/*
 * qib_twsi_blk_rd
 * Formerly called qib_eeprom_internal_read, and only used for eeprom,
 * but now the general interface for data transfer from twsi devices.
 * One vestige of its former role is that it recognizes a device
 * QIB_TWSI_NO_DEV and does the correct operation for the legacy part,
 * which responded to all TWSI device codes, interpreting them as
 * address within device. On all other devices found on board handled by
 * this driver, the device is followed by a one-byte "address" which selects
 * the "register" or "offset" within the device from which data should
 * be read.
 */
int qib_twsi_blk_rd(struct qib_devdata *dd, int dev, int addr,
		    void *buffer, int len)
{
	int ret;
	u8 *bp = buffer;

	ret = 1;

	if (dev == QIB_TWSI_NO_DEV) {
		/* legacy not-really-I2C */
		addr = (addr << 1) | READ_CMD;
		ret = qib_twsi_wr(dd, addr, QIB_TWSI_START);
	} else {
		/* Actual I2C */
		ret = qib_twsi_wr(dd, dev | WRITE_CMD, QIB_TWSI_START);
		if (ret) {
			stop_cmd(dd);
			ret = 1;
			goto bail;
		}
		/*
		 * SFF spec claims we do _not_ stop after the addr
		 * but simply issue a start with the "read" dev-addr.
		 * Since we are implicitely waiting for ACK here,
		 * we need t_buf (nominally 20uSec) before that start,
		 * and cannot rely on the delay built in to the STOP
		 */
		ret = qib_twsi_wr(dd, addr, 0);
		udelay(TWSI_BUF_WAIT_USEC);

		if (ret) {
			qib_dev_err(dd,
				"Failed to write interface read addr %02X\n",
				addr);
			ret = 1;
			goto bail;
		}
		ret = qib_twsi_wr(dd, dev | READ_CMD, QIB_TWSI_START);
	}
	if (ret) {
		stop_cmd(dd);
		ret = 1;
		goto bail;
	}

	/*
	 * block devices keeps clocking data out as long as we ack,
	 * automatically incrementing the address. Some have "pages"
	 * whose boundaries will not be crossed, but the handling
	 * of these is left to the caller, who is in a better
	 * position to know.
	 */
	while (len-- > 0) {
		/*
		 * Get and store data, sending ACK if length remaining,
		 * else STOP
		 */
		*bp++ = rd_byte(dd, !len);
	}

	ret = 0;

bail:
	return ret;
}

/*
 * qib_twsi_blk_wr
 * Formerly called qib_eeprom_internal_write, and only used for eeprom,
 * but now the general interface for data transfer to twsi devices.
 * One vestige of its former role is that it recognizes a device
 * QIB_TWSI_NO_DEV and does the correct operation for the legacy part,
 * which responded to all TWSI device codes, interpreting them as
 * address within device. On all other devices found on board handled by
 * this driver, the device is followed by a one-byte "address" which selects
 * the "register" or "offset" within the device to which data should
 * be written.
 */
int qib_twsi_blk_wr(struct qib_devdata *dd, int dev, int addr,
		    const void *buffer, int len)
{
	int sub_len;
	const u8 *bp = buffer;
	int max_wait_time, i;
	int ret = 1;

	while (len > 0) {
		if (dev == QIB_TWSI_NO_DEV) {
			if (qib_twsi_wr(dd, (addr << 1) | WRITE_CMD,
					QIB_TWSI_START)) {
				goto failed_write;
			}
		} else {
			/* Real I2C */
			if (qib_twsi_wr(dd, dev | WRITE_CMD, QIB_TWSI_START))
				goto failed_write;
			ret = qib_twsi_wr(dd, addr, 0);
			if (ret) {
				qib_dev_err(dd,
					"Failed to write interface write addr %02X\n",
					addr);
				goto failed_write;
			}
		}

		sub_len = min(len, 4);
		addr += sub_len;
		len -= sub_len;

		for (i = 0; i < sub_len; i++)
			if (qib_twsi_wr(dd, *bp++, 0))
				goto failed_write;

		stop_cmd(dd);

		/*
		 * Wait for write complete by waiting for a successful
		 * read (the chip replies with a zero after the write
		 * cmd completes, and before it writes to the eeprom.
		 * The startcmd for the read will fail the ack until
		 * the writes have completed.   We do this inline to avoid
		 * the debug prints that are in the real read routine
		 * if the startcmd fails.
		 * We also use the proper device address, so it doesn't matter
		 * whether we have real eeprom_dev. Legacy likes any address.
		 */
		max_wait_time = 100;
		while (qib_twsi_wr(dd, dev | READ_CMD, QIB_TWSI_START)) {
			stop_cmd(dd);
			if (!--max_wait_time)
				goto failed_write;
		}
		/* now read (and ignore) the resulting byte */
		rd_byte(dd, 1);
	}

	ret = 0;
	goto bail;

failed_write:
	stop_cmd(dd);
	ret = 1;

bail:
	return ret;
}