src/drivers/tpm/slb9635_i2c/tpm_tis_i2c.c - third_party/depthcharge - Git at Google

 /*
  * Copyright (C) 2011 Infineon Technologies
  *
  * Authors:
  * Peter Huewe <huewe.external@infineon.com>
  *
  * Description:
  * Device driver for TCG/TCPA TPM (trusted platform module).
  * Specifications at www.trustedcomputinggroup.org
  *
  * This device driver implements the TPM interface as defined in
  * the TCG TPM Interface Spec version 1.2, revision 1.0 and the
  * Infineon I2C Protocol Stack Specification v0.20.
  *
  * It is based on the Linux kernel driver tpm.c from Leendert van
  * Dorn, Dave Safford, Reiner Sailer, and Kyleen Hall.
  *
  * Version: 2.1.1
  *
  * See file CREDITS for list of people who contributed to this
  * project.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
  * published by the Free Software Foundation, version 2 of the
  * License.
  *
  * 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.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  * MA 02111-1307 USA
  */

 #include <libpayload.h>
 #include <endian.h>

 #include "drivers/bus/i2c/i2c.h"
 #include "drivers/tpm/slb9635_i2c/tpm.h"

 /* max. buffer size supported by our tpm */
 #ifdef TPM_BUFSIZE
 #undef TPM_BUFSIZE
 #endif
 #define TPM_BUFSIZE 1260
 /* Address of the TPM on the I2C bus */
 #define TPM_I2C_ADDR 0x20
 /* max. number of iterations after i2c NAK */
 #define MAX_COUNT 3

 #define SLEEP_DURATION 60 /*in usec*/

 /* max. number of iterations after i2c NAK for 'long' commands
  * we need this especially for sending TPM_READY, since the cleanup after the
  * transtion to the ready state may take some time, but it is unpredictable
  * how long it will take.
  */
 #define MAX_COUNT_LONG 50

 #define SLEEP_DURATION_LONG 210 /* in usec */

 /* expected value for DIDVID register */
 #define TPM_TIS_I2C_DID_VID_9635 0x000b15d1L
 #define TPM_TIS_I2C_DID_VID_9645 0x001a15d1L

 enum i2c_chip_type {
 	SLB9635,
 	SLB9645,
 	UNKNOWN,
 };

 static const char * const chip_name[] = {
 	[SLB9635] = "slb9635tt",
 	[SLB9645] = "slb9645tt",
 	[UNKNOWN] = "unknown/fallback to slb9635",
 };

 /* Structure to store I2C TPM specific stuff */
 struct tpm_inf_dev {
 	I2cOps *bus;
 	unsigned int addr;
 	uint8_t buf[TPM_BUFSIZE + sizeof(uint8_t)]; // max. buffer size + addr
 	enum i2c_chip_type chip_type;
 };

 static struct tpm_inf_dev tpm_dev = {
 	.addr = TPM_I2C_ADDR
 };

 /*
  * iic_tpm_read() - read from TPM register
  * @addr: register address to read from
  * @buffer: provided by caller
  * @len: number of bytes to read
  *
  * Read len bytes from TPM register and put them into
  * buffer (little-endian format, i.e. first byte is put into buffer[0]).
  *
  * NOTE: TPM is big-endian for multi-byte values. Multi-byte
  * values have to be swapped.
  *
  * Return -EIO on error, 0 on success.
  */
 int iic_tpm_read(uint8_t addr, uint8_t *buffer, size_t len)
 {
 	int rc;
 	int count;

 	if (!tpm_dev.bus)
 		return -1;
 	if ((tpm_dev.chip_type == SLB9635) || (tpm_dev.chip_type == UNKNOWN)) {
 		/* slb9635 protocol should work in both cases */
 		for (count = 0; count < MAX_COUNT; count++) {
 			rc = tpm_dev.bus->write(tpm_dev.bus, tpm_dev.addr,
 						0, 0, &addr, 1);
 			if (rc == 0)
 				break;  /* success, break to skip sleep */

 			udelay(SLEEP_DURATION);
 		}

 		if (rc)
 			return -rc;

 		/* After the TPM has successfully received the register address
 		 * it needs some time, thus we're sleeping here again, before
 		 * retrieving the data
 		 */
 		for (count = 0; count < MAX_COUNT; count++) {
 			udelay(SLEEP_DURATION);
 			rc = tpm_dev.bus->read(tpm_dev.bus, tpm_dev.addr,
 					       0, 0, buffer, len);
 			if (rc == 0)
 				break;  /* success, break to skip sleep */

 		}
 	} else {
 		/* use a combined read for newer chips
 		 * unfortunately the smbus functions are not suitable due to
 		 * the 32 byte limit of the smbus.
 		 * retries should usually not be needed, but are kept just to
 		 * be safe on the safe side.
 		 */
 		for (count = 0; count < MAX_COUNT; count++) {
 			rc = tpm_dev.bus->read(tpm_dev.bus, tpm_dev.addr,
 					       addr, 1, buffer, len);
 			if (rc == 0)
 				break;  /* break here to skip sleep */
 			udelay(SLEEP_DURATION);
 		}
 	}

 	/* take care of 'guard time' */
 	udelay(SLEEP_DURATION);
 	if (rc)
 		return -rc;

 	return 0;
 }

 static int iic_tpm_write_generic(uint8_t addr, uint8_t *buffer, size_t len,
 				unsigned int sleep_time,
 				uint8_t max_count)
 {
 	int rc = 0;
 	int count;

 	if (len > TPM_BUFSIZE) {
 		printf("%s: Length %d is too large\n", __func__, len);
 		return -1;
 	}

 	/* prepare send buffer */
 	tpm_dev.buf[0] = addr;
 	memcpy(&(tpm_dev.buf[1]), buffer, len);

 	if (!tpm_dev.bus)
 		return -1;
 	for (count = 0; count < max_count; count++) {
 		rc = tpm_dev.bus->write(tpm_dev.bus, tpm_dev.addr, 0, 0,
 					tpm_dev.buf, len + 1);
 		if (rc == 0)
 			break;  /* success, break to skip sleep */

 		udelay(sleep_time);
 	}

 	/* take care of 'guard time' */
 	udelay(SLEEP_DURATION);
 	if (rc)
 		return -rc;

 	return 0;
 }

 /*
  * iic_tpm_write() - write to TPM register
  * @addr: register address to write to
  * @buffer: containing data to be written
  * @len: number of bytes to write
  *
  * Write len bytes from provided buffer to TPM register (little
  * endian format, i.e. buffer[0] is written as first byte).
  *
  * NOTE: TPM is big-endian for multi-byte values. Multi-byte
  * values have to be swapped.
  *
  * NOTE: use this function instead of the iic_tpm_write_generic function.
  *
  * Return -EIO on error, 0 on success
  */
 static int iic_tpm_write(uint8_t addr, uint8_t *buffer, size_t len)
 {
 	return iic_tpm_write_generic(addr, buffer, len, SLEEP_DURATION,
 			MAX_COUNT);
 }

 /*
  * This function is needed especially for the cleanup situation after
  * sending TPM_READY
  * */
 static int iic_tpm_write_long(uint8_t addr, uint8_t *buffer, size_t len)
 {
 	return iic_tpm_write_generic(addr, buffer, len, SLEEP_DURATION_LONG,
 			MAX_COUNT_LONG);
 }

 #define TPM_HEADER_SIZE 10

 enum tis_access {
 	TPM_ACCESS_VALID = 0x80,
 	TPM_ACCESS_ACTIVE_LOCALITY = 0x20,
 	TPM_ACCESS_REQUEST_PENDING = 0x04,
 	TPM_ACCESS_REQUEST_USE = 0x02,
 };

 enum tis_status {
 	TPM_STS_VALID = 0x80,
 	TPM_STS_COMMAND_READY = 0x40,
 	TPM_STS_GO = 0x20,
 	TPM_STS_DATA_AVAIL = 0x10,
 	TPM_STS_DATA_EXPECT = 0x08,
 };

 enum tis_defaults {
 	TIS_SHORT_TIMEOUT = 750,	/* ms */
 	TIS_LONG_TIMEOUT = 2000,	/* 2 sec */
 };

 #define	TPM_ACCESS(l)			(0x0000 | ((l) << 4))
 #define	TPM_STS(l)			(0x0001 | ((l) << 4))
 #define	TPM_DATA_FIFO(l)		(0x0005 | ((l) << 4))
 #define	TPM_DID_VID(l)			(0x0006 | ((l) << 4))

 static int check_locality(struct tpm_chip *chip, int loc)
 {
 	uint8_t buf;
 	int rc;

 	rc = iic_tpm_read(TPM_ACCESS(loc), &buf, 1);
 	if (rc < 0)
 		return rc;

 	if ((buf & (TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID)) ==
 		(TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID)) {
 		chip->vendor.locality = loc;
 		return loc;
 	}

 	return -1;
 }

 static void release_locality(struct tpm_chip *chip, int loc, int force)
 {
 	uint8_t buf;
 	if (iic_tpm_read(TPM_ACCESS(loc), &buf, 1) < 0)
 		return;

 	if (force || (buf & (TPM_ACCESS_REQUEST_PENDING | TPM_ACCESS_VALID)) ==
 			(TPM_ACCESS_REQUEST_PENDING | TPM_ACCESS_VALID)) {
 		buf = TPM_ACCESS_ACTIVE_LOCALITY;
 		iic_tpm_write(TPM_ACCESS(loc), &buf, 1);
 	}
 }

 static int request_locality(struct tpm_chip *chip, int loc)
 {
 	uint8_t buf = TPM_ACCESS_REQUEST_USE;

 	if (check_locality(chip, loc) >= 0)
 		return loc; /* we already have the locality */

 	iic_tpm_write(TPM_ACCESS(loc), &buf, 1);

 	/* wait for burstcount */
 	int timeout = chip->vendor.timeout_a / TPM_TIMEOUT;
 	while (timeout) {
 		if (check_locality(chip, loc) >= 0)
 			return loc;
 		mdelay(TPM_TIMEOUT);
 		timeout--;
 	}

 	return -1;
 }

 static uint8_t tpm_tis_i2c_status(struct tpm_chip *chip)
 {
 	/* NOTE: since i2c read may fail, return 0 in this case --> time-out */
 	uint8_t buf;
 	if (iic_tpm_read(TPM_STS(chip->vendor.locality), &buf, 1) < 0)
 		return 0;
 	else
 		return buf;
 }

 static void tpm_tis_i2c_ready(struct tpm_chip *chip)
 {
 	/* this causes the current command to be aborted */
 	uint8_t buf = TPM_STS_COMMAND_READY;
 	iic_tpm_write_long(TPM_STS(chip->vendor.locality), &buf, 1);
 }

 static ssize_t get_burstcount(struct tpm_chip *chip)
 {
 	ssize_t burstcnt;
 	uint8_t buf[3];

 	/* wait for burstcount */
 	/* which timeout value, spec has 2 answers (c & d) */
 	int timeout = chip->vendor.timeout_d / TPM_TIMEOUT;
 	while (timeout) {
 		/* Note: STS is little endian */
 		if (iic_tpm_read(TPM_STS(chip->vendor.locality) + 1, buf, 3) < 0)
 			burstcnt = 0;
 		else
 			burstcnt = (buf[2] << 16) + (buf[1] << 8) + buf[0];

 		if (burstcnt)
 			return burstcnt;
 		mdelay(TPM_TIMEOUT);
 		timeout--;
 	}
 	return -1; //EBUSY;
 }

 static int wait_for_stat(struct tpm_chip *chip, uint8_t mask,
 			unsigned long timeout, int *status)
 {
 	/* check current status */
 	*status = tpm_tis_i2c_status(chip);
 	if ((*status & mask) == mask)
 		return 0;

 	timeout /= TPM_TIMEOUT;
 	while (timeout) {
 		mdelay(TPM_TIMEOUT);
 		*status = tpm_tis_i2c_status(chip);
 		if ((*status & mask) == mask)
 			return 0;
 		timeout--;
 	}

 	return -1; //ETIME;
 }

 static int recv_data(struct tpm_chip *chip, uint8_t *buf, size_t count)
 {
 	size_t size = 0;
 	ssize_t burstcnt;
 	int rc;

 	while (size < count) {
 		burstcnt = get_burstcount(chip);

 		/* burstcount < 0 = tpm is busy */
 		if (burstcnt < 0)
 			return burstcnt;

 		/* limit received data to max. left */
 		if (burstcnt > (count - size))
 			burstcnt = count - size;

 		rc = iic_tpm_read(TPM_DATA_FIFO(chip->vendor.locality),
 				  &(buf[size]),
 				  burstcnt);
 		if (rc == 0)
 			size += burstcnt;

 	}
 	return size;
 }

 static int tpm_tis_i2c_recv(struct tpm_chip *chip, uint8_t *buf, size_t count)
 {
 	int size = 0;
 	uint32_t expected;
 	int status;

 	if (count < TPM_HEADER_SIZE) {
 		size = -1; //EIO;
 		goto out;
 	}

 	/* read first 10 bytes, including tag, paramsize, and result */
 	size = recv_data(chip, buf, TPM_HEADER_SIZE);
 	if (size < TPM_HEADER_SIZE) {
 		printf("tpm_tis_i2c_recv: Unable to read header\n");
 		goto out;
 	}

 	memcpy(&expected, buf + TPM_RSP_SIZE_BYTE, sizeof(expected));
 	expected = betohl(expected);
 	if ((size_t)expected > count) {
 		size = -1; //EIO;
 		goto out;
 	}

 	size += recv_data(chip, &buf[TPM_HEADER_SIZE],
 				expected - TPM_HEADER_SIZE);
 	if (size < expected) {
 		printf("tpm_tis_i2c_recv: Unable to "
 			"read remainder of result\n");
 		size = -1; //ETIME;
 		goto out;
 	}

 	wait_for_stat(chip, TPM_STS_VALID, chip->vendor.timeout_c, &status);
 	if (status & TPM_STS_DATA_AVAIL) {	/* retry? */
 		printf("tpm_tis_i2c_recv: Error left over data\n");
 		size = -1; //EIO;
 		goto out;
 	}

 out:
 	tpm_tis_i2c_ready(chip);
 	/* The TPM needs some time to clean up here,
 	 * so we sleep rather than keeping the bus busy
 	 */
 	mdelay(2);
 	release_locality(chip, chip->vendor.locality, 0);

 	return size;
 }

 static int tpm_tis_i2c_send(struct tpm_chip *chip, uint8_t *buf, size_t len)
 {
 	int rc, status;
 	ssize_t burstcnt;
 	size_t count = 0;
 	uint8_t sts = TPM_STS_GO;

 	if (len > TPM_BUFSIZE)
 		return -1; //E2BIG; /* command is too long for our tpm, sorry */

 	if (request_locality(chip, 0) < 0)
 		return -1; //EBUSY;

 	status = tpm_tis_i2c_status(chip);
 	if ((status & TPM_STS_COMMAND_READY) == 0) {
 		tpm_tis_i2c_ready(chip);
 		if (wait_for_stat
 		    (chip, TPM_STS_COMMAND_READY,
 		     chip->vendor.timeout_b, &status) < 0) {
 			rc = -1; //ETIME;
 			goto out_err;
 		}
 	}

 	while (count < len - 1) {
 		burstcnt = get_burstcount(chip);

 		/* burstcount < 0 = tpm is busy */
 		if (burstcnt < 0)
 			return burstcnt;

 		if (burstcnt > (len-1-count))
 			burstcnt = len-1-count;

 #ifdef CONFIG_TPM_I2C_BURST_LIMITATION
 		if (burstcnt > CONFIG_TPM_I2C_BURST_LIMITATION)
 			burstcnt = CONFIG_TPM_I2C_BURST_LIMITATION;
 #endif /* CONFIG_TPM_I2C_BURST_LIMITATION */

 		rc = iic_tpm_write(TPM_DATA_FIFO(chip->vendor.locality),
 				   &(buf[count]), burstcnt);
 		if (rc == 0)
 			count += burstcnt;

 		wait_for_stat(chip, TPM_STS_VALID,
 				chip->vendor.timeout_c, &status);

 		if ((status & TPM_STS_DATA_EXPECT) == 0) {
 			rc = -1; //EIO;
 			goto out_err;
 		}

 	}

 	/* write last byte */
 	iic_tpm_write(TPM_DATA_FIFO(chip->vendor.locality), &(buf[count]), 1);
 	wait_for_stat(chip, TPM_STS_VALID, chip->vendor.timeout_c, &status);
 	if ((status & TPM_STS_DATA_EXPECT) != 0) {
 		rc = -1; //EIO;
 		goto out_err;
 	}

 	/* go and do it */
 	iic_tpm_write(TPM_STS(chip->vendor.locality), &sts, 1);

 	return len;
 out_err:
 	tpm_tis_i2c_ready(chip);
 	/* The TPM needs some time to clean up here,
 	 * so we sleep rather than keeping the bus busy
 	 */
 	mdelay(2);
 	release_locality(chip, chip->vendor.locality, 0);

 	return rc;
 }

 static struct tpm_vendor_specific tpm_tis_i2c = {
 	.status = tpm_tis_i2c_status,
 	.recv = tpm_tis_i2c_recv,
 	.send = tpm_tis_i2c_send,
 	.cancel = tpm_tis_i2c_ready,
 	.req_complete_mask = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
 	.req_complete_val = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
 	.req_canceled = TPM_STS_COMMAND_READY,
 };

 /* initialisation of i2c tpm */


 int tpm_vendor_init(I2cOps *bus, uint32_t dev_addr)
 {
 	uint32_t vendor;
 	unsigned int old_addr;
 	int rc = 0;
 	struct tpm_chip *chip;

 	old_addr = tpm_dev.addr;
 	if (dev_addr != 0)
 		tpm_dev.addr = dev_addr;
 	tpm_dev.bus = bus;

 	chip = tpm_register_hardware(&tpm_tis_i2c);
 	if (chip < 0) {
 		rc = -1; //ENODEV;
 		goto out_err;
 	}

 	/* Disable interrupts (not supported) */
 	chip->vendor.irq = 0;

 	/* Default timeouts */
 	chip->vendor.timeout_a = TIS_SHORT_TIMEOUT;
 	chip->vendor.timeout_b = TIS_LONG_TIMEOUT;
 	chip->vendor.timeout_c = TIS_SHORT_TIMEOUT;
 	chip->vendor.timeout_d = TIS_SHORT_TIMEOUT;

 	if (request_locality(chip, 0) != 0) {
 		rc = -1; //ENODEV;
 		goto out_err;
 	}

 	/* read four bytes from DID_VID register */
 	if (iic_tpm_read(TPM_DID_VID(0), (uint8_t *)&vendor, 4) < 0) {
 		rc = -1; //EIO;
 		goto out_release;
 	}

 	if (vendor == TPM_TIS_I2C_DID_VID_9645) {
 		tpm_dev.chip_type = SLB9645;
 	} else if (betohl(vendor) == TPM_TIS_I2C_DID_VID_9635) {
 		tpm_dev.chip_type = SLB9635;
 	} else {
 		printf("Vendor ID 0x%08x not recognized.\n", vendor);
 		rc = -1; //ENODEV;
 		goto out_release;
 	}

 	printf("1.2 TPM (chip type %s device-id 0x%X)\n",
 		 chip_name[tpm_dev.chip_type], vendor >> 16);

 	/*
 	 * A timeout query to TPM can be placed here.
 	 * Standard timeout values are used so far
 	 */

 	return 0;

 out_release:
 	release_locality(chip, 0, 1);

 out_err:
 	tpm_dev.addr = old_addr;
 	return rc;
 }

 void tpm_vendor_cleanup(struct tpm_chip *chip)
 {
 	release_locality(chip, chip->vendor.locality, 1);
 }
	/*
	* Copyright (C) 2011 Infineon Technologies
	*
	* Authors:
	* Peter Huewe <huewe.external@infineon.com>
	*
	* Description:
	* Device driver for TCG/TCPA TPM (trusted platform module).
	* Specifications at www.trustedcomputinggroup.org
	*
	* This device driver implements the TPM interface as defined in
	* the TCG TPM Interface Spec version 1.2, revision 1.0 and the
	* Infineon I2C Protocol Stack Specification v0.20.
	*
	* It is based on the Linux kernel driver tpm.c from Leendert van
	* Dorn, Dave Safford, Reiner Sailer, and Kyleen Hall.
	*
	* Version: 2.1.1
	*
	* See file CREDITS for list of people who contributed to this
	* project.
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License as
	* published by the Free Software Foundation, version 2 of the
	* License.
	*
	* 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.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
	* MA 02111-1307 USA
	*/

	#include <libpayload.h>
	#include <endian.h>

	#include "drivers/bus/i2c/i2c.h"
	#include "drivers/tpm/slb9635_i2c/tpm.h"

	/* max. buffer size supported by our tpm */
	#ifdef TPM_BUFSIZE
	#undef TPM_BUFSIZE
	#endif
	#define TPM_BUFSIZE 1260
	/* Address of the TPM on the I2C bus */
	#define TPM_I2C_ADDR 0x20
	/* max. number of iterations after i2c NAK */
	#define MAX_COUNT 3

	#define SLEEP_DURATION 60 /in usec/

	/* max. number of iterations after i2c NAK for 'long' commands
	* we need this especially for sending TPM_READY, since the cleanup after the
	* transtion to the ready state may take some time, but it is unpredictable
	* how long it will take.
	*/
	#define MAX_COUNT_LONG 50

	#define SLEEP_DURATION_LONG 210 /* in usec */

	/* expected value for DIDVID register */
	#define TPM_TIS_I2C_DID_VID_9635 0x000b15d1L
	#define TPM_TIS_I2C_DID_VID_9645 0x001a15d1L

	enum i2c_chip_type {
	SLB9635,
	SLB9645,
	UNKNOWN,
	};

	static const char * const chip_name[] = {
	[SLB9635] = "slb9635tt",
	[SLB9645] = "slb9645tt",
	[UNKNOWN] = "unknown/fallback to slb9635",
	};

	/* Structure to store I2C TPM specific stuff */
	struct tpm_inf_dev {
	I2cOps *bus;
	unsigned int addr;
	uint8_t buf[TPM_BUFSIZE + sizeof(uint8_t)]; // max. buffer size + addr
	enum i2c_chip_type chip_type;
	};

	static struct tpm_inf_dev tpm_dev = {
	.addr = TPM_I2C_ADDR
	};

	/*
	* iic_tpm_read() - read from TPM register
	* @addr: register address to read from
	* @buffer: provided by caller
	* @len: number of bytes to read
	*
	* Read len bytes from TPM register and put them into
	* buffer (little-endian format, i.e. first byte is put into buffer[0]).
	*
	* NOTE: TPM is big-endian for multi-byte values. Multi-byte
	* values have to be swapped.
	*
	* Return -EIO on error, 0 on success.
	*/
	int iic_tpm_read(uint8_t addr, uint8_t *buffer, size_t len)
	{
	int rc;
	int count;

	if (!tpm_dev.bus)
	return -1;
	if ((tpm_dev.chip_type == SLB9635) \|\| (tpm_dev.chip_type == UNKNOWN)) {
	/* slb9635 protocol should work in both cases */
	for (count = 0; count < MAX_COUNT; count++) {
	rc = tpm_dev.bus->write(tpm_dev.bus, tpm_dev.addr,
	0, 0, &addr, 1);
	if (rc == 0)
	break; /* success, break to skip sleep */

	udelay(SLEEP_DURATION);
	}

	if (rc)
	return -rc;

	/* After the TPM has successfully received the register address
	* it needs some time, thus we're sleeping here again, before
	* retrieving the data
	*/
	for (count = 0; count < MAX_COUNT; count++) {
	udelay(SLEEP_DURATION);
	rc = tpm_dev.bus->read(tpm_dev.bus, tpm_dev.addr,
	0, 0, buffer, len);
	if (rc == 0)
	break; /* success, break to skip sleep */

	}
	} else {
	/* use a combined read for newer chips
	* unfortunately the smbus functions are not suitable due to
	* the 32 byte limit of the smbus.
	* retries should usually not be needed, but are kept just to
	* be safe on the safe side.
	*/
	for (count = 0; count < MAX_COUNT; count++) {
	rc = tpm_dev.bus->read(tpm_dev.bus, tpm_dev.addr,
	addr, 1, buffer, len);
	if (rc == 0)
	break; /* break here to skip sleep */
	udelay(SLEEP_DURATION);
	}
	}

	/* take care of 'guard time' */
	udelay(SLEEP_DURATION);
	if (rc)
	return -rc;

	return 0;
	}

	static int iic_tpm_write_generic(uint8_t addr, uint8_t *buffer, size_t len,
	unsigned int sleep_time,
	uint8_t max_count)
	{
	int rc = 0;
	int count;

	if (len > TPM_BUFSIZE) {
	printf("%s: Length %d is too large\n", __func__, len);
	return -1;
	}

	/* prepare send buffer */
	tpm_dev.buf[0] = addr;
	memcpy(&(tpm_dev.buf[1]), buffer, len);

	if (!tpm_dev.bus)
	return -1;
	for (count = 0; count < max_count; count++) {
	rc = tpm_dev.bus->write(tpm_dev.bus, tpm_dev.addr, 0, 0,
	tpm_dev.buf, len + 1);
	if (rc == 0)
	break; /* success, break to skip sleep */

	udelay(sleep_time);
	}

	/* take care of 'guard time' */
	udelay(SLEEP_DURATION);
	if (rc)
	return -rc;

	return 0;
	}

	/*
	* iic_tpm_write() - write to TPM register
	* @addr: register address to write to
	* @buffer: containing data to be written
	* @len: number of bytes to write
	*
	* Write len bytes from provided buffer to TPM register (little
	* endian format, i.e. buffer[0] is written as first byte).
	*
	* NOTE: TPM is big-endian for multi-byte values. Multi-byte
	* values have to be swapped.
	*
	* NOTE: use this function instead of the iic_tpm_write_generic function.
	*
	* Return -EIO on error, 0 on success
	*/
	static int iic_tpm_write(uint8_t addr, uint8_t *buffer, size_t len)
	{
	return iic_tpm_write_generic(addr, buffer, len, SLEEP_DURATION,
	MAX_COUNT);
	}

	/*
	* This function is needed especially for the cleanup situation after
	* sending TPM_READY
	* */
	static int iic_tpm_write_long(uint8_t addr, uint8_t *buffer, size_t len)
	{
	return iic_tpm_write_generic(addr, buffer, len, SLEEP_DURATION_LONG,
	MAX_COUNT_LONG);
	}

	#define TPM_HEADER_SIZE 10

	enum tis_access {
	TPM_ACCESS_VALID = 0x80,
	TPM_ACCESS_ACTIVE_LOCALITY = 0x20,
	TPM_ACCESS_REQUEST_PENDING = 0x04,
	TPM_ACCESS_REQUEST_USE = 0x02,
	};

	enum tis_status {
	TPM_STS_VALID = 0x80,
	TPM_STS_COMMAND_READY = 0x40,
	TPM_STS_GO = 0x20,
	TPM_STS_DATA_AVAIL = 0x10,
	TPM_STS_DATA_EXPECT = 0x08,
	};

	enum tis_defaults {
	TIS_SHORT_TIMEOUT = 750, /* ms */
	TIS_LONG_TIMEOUT = 2000, /* 2 sec */
	};

	#define TPM_ACCESS(l) (0x0000 \| ((l) << 4))
	#define TPM_STS(l) (0x0001 \| ((l) << 4))
	#define TPM_DATA_FIFO(l) (0x0005 \| ((l) << 4))
	#define TPM_DID_VID(l) (0x0006 \| ((l) << 4))

	static int check_locality(struct tpm_chip *chip, int loc)
	{
	uint8_t buf;
	int rc;

	rc = iic_tpm_read(TPM_ACCESS(loc), &buf, 1);
	if (rc < 0)
	return rc;

	if ((buf & (TPM_ACCESS_ACTIVE_LOCALITY \| TPM_ACCESS_VALID)) ==
	(TPM_ACCESS_ACTIVE_LOCALITY \| TPM_ACCESS_VALID)) {
	chip->vendor.locality = loc;
	return loc;
	}

	return -1;
	}

	static void release_locality(struct tpm_chip *chip, int loc, int force)
	{
	uint8_t buf;
	if (iic_tpm_read(TPM_ACCESS(loc), &buf, 1) < 0)
	return;

	if (force \|\| (buf & (TPM_ACCESS_REQUEST_PENDING \| TPM_ACCESS_VALID)) ==
	(TPM_ACCESS_REQUEST_PENDING \| TPM_ACCESS_VALID)) {
	buf = TPM_ACCESS_ACTIVE_LOCALITY;
	iic_tpm_write(TPM_ACCESS(loc), &buf, 1);
	}
	}

	static int request_locality(struct tpm_chip *chip, int loc)
	{
	uint8_t buf = TPM_ACCESS_REQUEST_USE;

	if (check_locality(chip, loc) >= 0)
	return loc; /* we already have the locality */

	iic_tpm_write(TPM_ACCESS(loc), &buf, 1);

	/* wait for burstcount */
	int timeout = chip->vendor.timeout_a / TPM_TIMEOUT;
	while (timeout) {
	if (check_locality(chip, loc) >= 0)
	return loc;
	mdelay(TPM_TIMEOUT);
	timeout--;
	}

	return -1;
	}

	static uint8_t tpm_tis_i2c_status(struct tpm_chip *chip)
	{
	/* NOTE: since i2c read may fail, return 0 in this case --> time-out */
	uint8_t buf;
	if (iic_tpm_read(TPM_STS(chip->vendor.locality), &buf, 1) < 0)
	return 0;
	else
	return buf;
	}

	static void tpm_tis_i2c_ready(struct tpm_chip *chip)
	{
	/* this causes the current command to be aborted */
	uint8_t buf = TPM_STS_COMMAND_READY;
	iic_tpm_write_long(TPM_STS(chip->vendor.locality), &buf, 1);
	}

	static ssize_t get_burstcount(struct tpm_chip *chip)
	{
	ssize_t burstcnt;
	uint8_t buf[3];

	/* wait for burstcount */
	/* which timeout value, spec has 2 answers (c & d) */
	int timeout = chip->vendor.timeout_d / TPM_TIMEOUT;
	while (timeout) {
	/* Note: STS is little endian */
	if (iic_tpm_read(TPM_STS(chip->vendor.locality) + 1, buf, 3) < 0)
	burstcnt = 0;
	else
	burstcnt = (buf[2] << 16) + (buf[1] << 8) + buf[0];

	if (burstcnt)
	return burstcnt;
	mdelay(TPM_TIMEOUT);
	timeout--;
	}
	return -1; //EBUSY;
	}

	static int wait_for_stat(struct tpm_chip *chip, uint8_t mask,
	unsigned long timeout, int *status)
	{
	/* check current status */
	*status = tpm_tis_i2c_status(chip);
	if ((*status & mask) == mask)
	return 0;

	timeout /= TPM_TIMEOUT;
	while (timeout) {
	mdelay(TPM_TIMEOUT);
	*status = tpm_tis_i2c_status(chip);
	if ((*status & mask) == mask)
	return 0;
	timeout--;
	}

	return -1; //ETIME;
	}

	static int recv_data(struct tpm_chip chip, uint8_t buf, size_t count)
	{
	size_t size = 0;
	ssize_t burstcnt;
	int rc;

	while (size < count) {
	burstcnt = get_burstcount(chip);

	/* burstcount < 0 = tpm is busy */
	if (burstcnt < 0)
	return burstcnt;

	/* limit received data to max. left */
	if (burstcnt > (count - size))
	burstcnt = count - size;

	rc = iic_tpm_read(TPM_DATA_FIFO(chip->vendor.locality),
	&(buf[size]),
	burstcnt);
	if (rc == 0)
	size += burstcnt;

	}
	return size;
	}

	static int tpm_tis_i2c_recv(struct tpm_chip chip, uint8_t buf, size_t count)
	{
	int size = 0;
	uint32_t expected;
	int status;

	if (count < TPM_HEADER_SIZE) {
	size = -1; //EIO;
	goto out;
	}

	/* read first 10 bytes, including tag, paramsize, and result */
	size = recv_data(chip, buf, TPM_HEADER_SIZE);
	if (size < TPM_HEADER_SIZE) {
	printf("tpm_tis_i2c_recv: Unable to read header\n");
	goto out;
	}

	memcpy(&expected, buf + TPM_RSP_SIZE_BYTE, sizeof(expected));
	expected = betohl(expected);
	if ((size_t)expected > count) {
	size = -1; //EIO;
	goto out;
	}

	size += recv_data(chip, &buf[TPM_HEADER_SIZE],
	expected - TPM_HEADER_SIZE);
	if (size < expected) {
	printf("tpm_tis_i2c_recv: Unable to "
	"read remainder of result\n");
	size = -1; //ETIME;
	goto out;
	}

	wait_for_stat(chip, TPM_STS_VALID, chip->vendor.timeout_c, &status);
	if (status & TPM_STS_DATA_AVAIL) { /* retry? */
	printf("tpm_tis_i2c_recv: Error left over data\n");
	size = -1; //EIO;
	goto out;
	}

	out:
	tpm_tis_i2c_ready(chip);
	/* The TPM needs some time to clean up here,
	* so we sleep rather than keeping the bus busy
	*/
	mdelay(2);
	release_locality(chip, chip->vendor.locality, 0);

	return size;
	}

	static int tpm_tis_i2c_send(struct tpm_chip chip, uint8_t buf, size_t len)
	{
	int rc, status;
	ssize_t burstcnt;
	size_t count = 0;
	uint8_t sts = TPM_STS_GO;

	if (len > TPM_BUFSIZE)
	return -1; //E2BIG; /* command is too long for our tpm, sorry */

	if (request_locality(chip, 0) < 0)
	return -1; //EBUSY;

	status = tpm_tis_i2c_status(chip);
	if ((status & TPM_STS_COMMAND_READY) == 0) {
	tpm_tis_i2c_ready(chip);
	if (wait_for_stat
	(chip, TPM_STS_COMMAND_READY,
	chip->vendor.timeout_b, &status) < 0) {
	rc = -1; //ETIME;
	goto out_err;
	}
	}

	while (count < len - 1) {
	burstcnt = get_burstcount(chip);

	/* burstcount < 0 = tpm is busy */
	if (burstcnt < 0)
	return burstcnt;

	if (burstcnt > (len-1-count))
	burstcnt = len-1-count;

	#ifdef CONFIG_TPM_I2C_BURST_LIMITATION
	if (burstcnt > CONFIG_TPM_I2C_BURST_LIMITATION)
	burstcnt = CONFIG_TPM_I2C_BURST_LIMITATION;
	#endif /* CONFIG_TPM_I2C_BURST_LIMITATION */

	rc = iic_tpm_write(TPM_DATA_FIFO(chip->vendor.locality),
	&(buf[count]), burstcnt);
	if (rc == 0)
	count += burstcnt;

	wait_for_stat(chip, TPM_STS_VALID,
	chip->vendor.timeout_c, &status);

	if ((status & TPM_STS_DATA_EXPECT) == 0) {
	rc = -1; //EIO;
	goto out_err;
	}

	}

	/* write last byte */
	iic_tpm_write(TPM_DATA_FIFO(chip->vendor.locality), &(buf[count]), 1);
	wait_for_stat(chip, TPM_STS_VALID, chip->vendor.timeout_c, &status);
	if ((status & TPM_STS_DATA_EXPECT) != 0) {
	rc = -1; //EIO;
	goto out_err;
	}

	/* go and do it */
	iic_tpm_write(TPM_STS(chip->vendor.locality), &sts, 1);

	return len;
	out_err:
	tpm_tis_i2c_ready(chip);
	/* The TPM needs some time to clean up here,
	* so we sleep rather than keeping the bus busy
	*/
	mdelay(2);
	release_locality(chip, chip->vendor.locality, 0);

	return rc;
	}

	static struct tpm_vendor_specific tpm_tis_i2c = {
	.status = tpm_tis_i2c_status,
	.recv = tpm_tis_i2c_recv,
	.send = tpm_tis_i2c_send,
	.cancel = tpm_tis_i2c_ready,
	.req_complete_mask = TPM_STS_DATA_AVAIL \| TPM_STS_VALID,
	.req_complete_val = TPM_STS_DATA_AVAIL \| TPM_STS_VALID,
	.req_canceled = TPM_STS_COMMAND_READY,
	};

	/* initialisation of i2c tpm */


	int tpm_vendor_init(I2cOps *bus, uint32_t dev_addr)
	{
	uint32_t vendor;
	unsigned int old_addr;
	int rc = 0;
	struct tpm_chip *chip;

	old_addr = tpm_dev.addr;
	if (dev_addr != 0)
	tpm_dev.addr = dev_addr;
	tpm_dev.bus = bus;

	chip = tpm_register_hardware(&tpm_tis_i2c);
	if (chip < 0) {
	rc = -1; //ENODEV;
	goto out_err;
	}

	/* Disable interrupts (not supported) */
	chip->vendor.irq = 0;

	/* Default timeouts */
	chip->vendor.timeout_a = TIS_SHORT_TIMEOUT;
	chip->vendor.timeout_b = TIS_LONG_TIMEOUT;
	chip->vendor.timeout_c = TIS_SHORT_TIMEOUT;
	chip->vendor.timeout_d = TIS_SHORT_TIMEOUT;

	if (request_locality(chip, 0) != 0) {
	rc = -1; //ENODEV;
	goto out_err;
	}

	/* read four bytes from DID_VID register */
	if (iic_tpm_read(TPM_DID_VID(0), (uint8_t *)&vendor, 4) < 0) {
	rc = -1; //EIO;
	goto out_release;
	}

	if (vendor == TPM_TIS_I2C_DID_VID_9645) {
	tpm_dev.chip_type = SLB9645;
	} else if (betohl(vendor) == TPM_TIS_I2C_DID_VID_9635) {
	tpm_dev.chip_type = SLB9635;
	} else {
	printf("Vendor ID 0x%08x not recognized.\n", vendor);
	rc = -1; //ENODEV;
	goto out_release;
	}

	printf("1.2 TPM (chip type %s device-id 0x%X)\n",
	chip_name[tpm_dev.chip_type], vendor >> 16);

	/*
	* A timeout query to TPM can be placed here.
	* Standard timeout values are used so far
	*/

	return 0;

	out_release:
	release_locality(chip, 0, 1);

	out_err:
	tpm_dev.addr = old_addr;
	return rc;
	}

	void tpm_vendor_cleanup(struct tpm_chip *chip)
	{
	release_locality(chip, chip->vendor.locality, 1);
	}