twsi.c

/*
 * Copyright(c) 2015, 2016 Intel Corporation.
 *
 * This file is provided under a dual BSD/GPLv2 license.  When using or
 * redistributing this file, you may do so under either license.
 *
 * GPL LICENSE SUMMARY
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * BSD LICENSE
 *
 * 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.
 *  - Neither the name of Intel Corporation nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "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 COPYRIGHT
 * OWNER OR CONTRIBUTORS 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.
 *
 */

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

#include "hfi.h"
#include "twsi.h"

/*
 * "Two Wire Serial Interface" support.
 *
 * 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 hfi1_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 hfi1_devdata *dd, u32 target)
{
	/*
	 * implicit read of EXTStatus is as good as explicit
	 * read of scratch, if all we want to do is flush
	 * writes.
	 */
	hfi1_gpio_mod(dd, target, 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 hfi1_devdata *dd, u32 target, u8 bit)
{
	u32 mask;

	udelay(1);

	mask = QSFP_HFI0_I2CCLK;

	/* SCL is meant to be bare-drain, so never set "OUT", just DIR */
	hfi1_gpio_mod(dd, target, 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 & hfi1_gpio_mod(dd, target, 0, 0, 0))
				break;
			udelay(2);
		}
		if (rise_usec <= 0)
			dd_dev_err(dd, "SCL interface stuck low > %d uSec\n",
				   SCL_WAIT_USEC);
	}
	i2c_wait_for_writes(dd, target);
}

static u8 scl_in(struct hfi1_devdata *dd, u32 target, int wait)
{
	u32 read_val, mask;

	mask = QSFP_HFI0_I2CCLK;
	/* SCL is meant to be bare-drain, so never set "OUT", just DIR */
	hfi1_gpio_mod(dd, target, 0, 0, mask);
	read_val = hfi1_gpio_mod(dd, target, 0, 0, 0);
	if (wait)
		i2c_wait_for_writes(dd, target);
	return (read_val & mask) >> GPIO_SCL_NUM;
}

static void sda_out(struct hfi1_devdata *dd, u32 target, u8 bit)
{
	u32 mask;

	mask = QSFP_HFI0_I2CDAT;

	/* SDA is meant to be bare-drain, so never set "OUT", just DIR */
	hfi1_gpio_mod(dd, target, 0, bit ? 0 : mask, mask);

	i2c_wait_for_writes(dd, target);
	udelay(2);
}

static u8 sda_in(struct hfi1_devdata *dd, u32 target, int wait)
{
	u32 read_val, mask;

	mask = QSFP_HFI0_I2CDAT;
	/* SDA is meant to be bare-drain, so never set "OUT", just DIR */
	hfi1_gpio_mod(dd, target, 0, 0, mask);
	read_val = hfi1_gpio_mod(dd, target, 0, 0, 0);
	if (wait)
		i2c_wait_for_writes(dd, target);
	return (read_val & mask) >> GPIO_SDA_NUM;
}

/**
 * i2c_ackrcv - see if ack following write is true
 * @dd: the hfi1_ib device
 */
static int i2c_ackrcv(struct hfi1_devdata *dd, u32 target)
{
	u8 ack_received;

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

static void stop_cmd(struct hfi1_devdata *dd, u32 target);

/**
 * rd_byte - read a byte, sending STOP on last, else ACK
 * @dd: the hfi1_ib device
 *
 * Returns byte shifted out of device
 */
static int rd_byte(struct hfi1_devdata *dd, u32 target, int last)
{
	int bit_cntr, data;

	data = 0;

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

/**
 * wr_byte - write a byte, one bit at a time
 * @dd: the hfi1_ib device
 * @data: the byte to write
 *
 * Returns 0 if we got the following ack, otherwise 1
 */
static int wr_byte(struct hfi1_devdata *dd, u32 target, u8 data)
{
	int bit_cntr;
	u8 bit;

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

/*
 * issue TWSI start sequence:
 * (both clock/data high, clock high, data low while clock is high)
 */
static void start_seq(struct hfi1_devdata *dd, u32 target)
{
	sda_out(dd, target, 1);
	scl_out(dd, target, 1);
	sda_out(dd, target, 0);
	udelay(1);
	scl_out(dd, target, 0);
}

/**
 * stop_seq - transmit the stop sequence
 * @dd: the hfi1_ib device
 *
 * (both clock/data low, clock high, data high while clock is high)
 */
static void stop_seq(struct hfi1_devdata *dd, u32 target)
{
	scl_out(dd, target, 0);
	sda_out(dd, target, 0);
	scl_out(dd, target, 1);
	sda_out(dd, target, 1);
}

/**
 * stop_cmd - transmit the stop condition
 * @dd: the hfi1_ib device
 *
 * (both clock/data low, clock high, data high while clock is high)
 */
static void stop_cmd(struct hfi1_devdata *dd, u32 target)
{
	stop_seq(dd, target);
	udelay(TWSI_BUF_WAIT_USEC);
}

/**
 * hfi1_twsi_reset - reset I2C communication
 * @dd: the hfi1_ib device
 * returns 0 if ok, -EIO on error
 */
int hfi1_twsi_reset(struct hfi1_devdata *dd, u32 target)
{
	int clock_cycles_left = 9;
	u32 mask;

	/* Both SCL and SDA should be high. If not, there
	 * is something wrong.
	 */
	mask = QSFP_HFI0_I2CCLK | QSFP_HFI0_I2CDAT;

	/*
	 * 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)
	 */
	hfi1_gpio_mod(dd, target, 0, 0, mask);

	/* Check if SCL is low, if it is low then we have a slave device
	 * misbehaving and there is not much we can do.
	 */
	if (!scl_in(dd, target, 0))
		return -EIO;

	/* Check if SDA is low, if it is low then we have to clock SDA
	 * up to 9 times for the device to release the bus
	 */
	while (clock_cycles_left--) {
		if (sda_in(dd, target, 0))
			return 0;
		scl_out(dd, target, 0);
		scl_out(dd, target, 1);
	}

	return -EIO;
}

#define HFI1_TWSI_START 0x100
#define HFI1_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 twsi_wr(struct hfi1_devdata *dd, u32 target, int data, int flags)
{
	int ret = 1;

	if (flags & HFI1_TWSI_START)
		start_seq(dd, target);

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

	if (flags & HFI1_TWSI_STOP)
		stop_cmd(dd, target);
	return ret;
}

/* Added functionality for IBA7220-based cards */
#define HFI1_TEMP_DEV 0x98

/*
 * hfi1_twsi_blk_rd
 * General interface for data transfer from twsi devices.
 * One vestige of its former role is that it recognizes a device
 * HFI1_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 N-byte "address" which selects
 * the "register" or "offset" within the device from which data should
 * be read.
 */
int hfi1_twsi_blk_rd(struct hfi1_devdata *dd, u32 target, int dev, int addr,
		     void *buffer, int len)
{
	u8 *bp = buffer;
	int ret = 1;
	int i;
	int offset_size;

	/* obtain the offset size, strip it from the device address */
	offset_size = (dev >> 8) & 0xff;
	dev &= 0xff;

	/* allow at most a 2 byte offset */
	if (offset_size > 2)
		goto bail;

	if (dev == HFI1_TWSI_NO_DEV) {
		/* legacy not-really-I2C */
		addr = (addr << 1) | READ_CMD;
		ret = twsi_wr(dd, target, addr, HFI1_TWSI_START);
	} else {
		/* Actual I2C */
		if (offset_size) {
			ret = twsi_wr(dd, target,
				      dev | WRITE_CMD, HFI1_TWSI_START);
			if (ret) {
				stop_cmd(dd, target);
				goto bail;
			}

			for (i = 0; i < offset_size; i++) {
				ret = twsi_wr(dd, target,
					      (addr >> (i * 8)) & 0xff, 0);
				udelay(TWSI_BUF_WAIT_USEC);
				if (ret) {
					dd_dev_err(dd, "Failed to write byte %d of offset 0x%04X\n",
						   i, addr);
					goto bail;
				}
			}
		}
		ret = twsi_wr(dd, target, dev | READ_CMD, HFI1_TWSI_START);
	}
	if (ret) {
		stop_cmd(dd, target);
		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, target, !len);
	}

	ret = 0;

bail:
	return ret;
}

/*
 * hfi1_twsi_blk_wr
 * General interface for data transfer to twsi devices.
 * One vestige of its former role is that it recognizes a device
 * HFI1_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 N-byte "address" which selects
 * the "register" or "offset" within the device to which data should
 * be written.
 */
int hfi1_twsi_blk_wr(struct hfi1_devdata *dd, u32 target, int dev, int addr,
		     const void *buffer, int len)
{
	const u8 *bp = buffer;
	int ret = 1;
	int i;
	int offset_size;

	/* obtain the offset size, strip it from the device address */
	offset_size = (dev >> 8) & 0xff;
	dev &= 0xff;

	/* allow at most a 2 byte offset */
	if (offset_size > 2)
		goto bail;

	if (dev == HFI1_TWSI_NO_DEV) {
		if (twsi_wr(dd, target, (addr << 1) | WRITE_CMD,
			    HFI1_TWSI_START)) {
			goto failed_write;
		}
	} else {
		/* Real I2C */
		if (twsi_wr(dd, target, dev | WRITE_CMD, HFI1_TWSI_START))
			goto failed_write;
	}

	for (i = 0; i < offset_size; i++) {
		ret = twsi_wr(dd, target, (addr >> (i * 8)) & 0xff, 0);
		udelay(TWSI_BUF_WAIT_USEC);
		if (ret) {
			dd_dev_err(dd, "Failed to write byte %d of offset 0x%04X\n",
				   i, addr);
			goto bail;
		}
	}

	for (i = 0; i < len; i++)
		if (twsi_wr(dd, target, *bp++, 0))
			goto failed_write;

	ret = 0;

failed_write:
	stop_cmd(dd, target);

bail:
	return ret;
}