path: root/drivers/char/tpm/tpm_i2c_infineon.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012,2013 Infineon Technologies
 *
 * Authors:
 * Peter Huewe <peter.huewe@infineon.com>
 *
 * 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 original tpm_tis device driver from Leendert van
 * Dorn and Kyleen Hall.
 */
#include <linux/i2c.h>
#include <linux/module.h>
#include <linux/wait.h>
#include "tpm.h"

#define TPM_I2C_INFINEON_BUFSIZE 1260

/* max. number of iterations after I2C NAK */
#define MAX_COUNT 3

#define SLEEP_DURATION_LOW 55
#define SLEEP_DURATION_HI 65

/* 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_LOW 200
#define SLEEP_DURATION_LONG_HI 220

/* After sending TPM_READY to 'reset' the TPM we have to sleep even longer */
#define SLEEP_DURATION_RESET_LOW 2400
#define SLEEP_DURATION_RESET_HI 2600

/* we want to use usleep_range instead of msleep for the 5ms TPM_TIMEOUT */
#define TPM_TIMEOUT_US_LOW (TPM_TIMEOUT * 1000)
#define TPM_TIMEOUT_US_HI  (TPM_TIMEOUT_US_LOW + 2000)

/* expected value for DIDVID register */
#define TPM_TIS_I2C_DID_VID_9635 0xd1150b00L
#define TPM_TIS_I2C_DID_VID_9645 0x001a15d1L

enum i2c_chip_type {
	SLB9635,
	SLB9645,
	UNKNOWN,
};

struct tpm_inf_dev {
	struct i2c_client *client;
	int locality;
	/* In addition to the data itself, the buffer must fit the 7-bit I2C
	 * address and the direction bit.
	 */
	u8 buf[TPM_I2C_INFINEON_BUFSIZE + 1];
	struct tpm_chip *chip;
	enum i2c_chip_type chip_type;
	unsigned int adapterlimit;
};

static struct tpm_inf_dev tpm_dev;

/*
 * 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.
 *
 * NOTE: We can't unfortunately use the combined read/write functions
 * provided by the i2c core as the TPM currently does not support the
 * repeated start condition and due to it's special requirements.
 * The i2c_smbus* functions do not work for this chip.
 *
 * Return -EIO on error, 0 on success.
 */
static int iic_tpm_read(u8 addr, u8 *buffer, size_t len)
{

	struct i2c_msg msg1 = {
		.addr = tpm_dev.client->addr,
		.len = 1,
		.buf = &addr
	};
	struct i2c_msg msg2 = {
		.addr = tpm_dev.client->addr,
		.flags = I2C_M_RD,
		.len = len,
		.buf = buffer
	};
	struct i2c_msg msgs[] = {msg1, msg2};

	int rc = 0;
	int count;
	unsigned int msglen = len;

	/* Lock the adapter for the duration of the whole sequence. */
	if (!tpm_dev.client->adapter->algo->master_xfer)
		return -EOPNOTSUPP;
	i2c_lock_bus(tpm_dev.client->adapter, I2C_LOCK_SEGMENT);

	if (tpm_dev.chip_type == SLB9645) {
		/* 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 on the safe side.
		 */
		for (count = 0; count < MAX_COUNT; count++) {
			rc = __i2c_transfer(tpm_dev.client->adapter, msgs, 2);
			if (rc > 0)
				break;	/* break here to skip sleep */
			usleep_range(SLEEP_DURATION_LOW, SLEEP_DURATION_HI);
		}
	} else {
		/* Expect to send one command message and one data message, but
		 * support looping over each or both if necessary.
		 */
		while (len > 0) {
			/* slb9635 protocol should work in all cases */
			for (count = 0; count < MAX_COUNT; count++) {
				rc = __i2c_transfer(tpm_dev.client->adapter,
						    &msg1, 1);
				if (rc > 0)
					break;	/* break here to skip sleep */

				usleep_range(SLEEP_DURATION_LOW,
					     SLEEP_DURATION_HI);
			}

			if (rc <= 0)
				goto out;

			/* 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++) {
				if (tpm_dev.adapterlimit) {
					msglen = min_t(unsigned int,
						       tpm_dev.adapterlimit,
						       len);
					msg2.len = msglen;
				}
				usleep_range(SLEEP_DURATION_LOW,
					     SLEEP_DURATION_HI);
				rc = __i2c_transfer(tpm_dev.client->adapter,
						    &msg2, 1);
				if (rc > 0) {
					/* Since len is unsigned, make doubly
					 * sure we do not underflow it.
					 */
					if (msglen > len)
						len = 0;
					else
						len -= msglen;
					msg2.buf += msglen;
					break;
				}
				/* If the I2C adapter rejected the request (e.g
				 * when the quirk read_max_len < len) fall back
				 * to a sane minimum value and try again.
				 */
				if (rc == -EOPNOTSUPP)
					tpm_dev.adapterlimit =
							I2C_SMBUS_BLOCK_MAX;
			}

			if (rc <= 0)
				goto out;
		}
	}

out:
	i2c_unlock_bus(tpm_dev.client->adapter, I2C_LOCK_SEGMENT);
	/* take care of 'guard time' */
	usleep_range(SLEEP_DURATION_LOW, SLEEP_DURATION_HI);

	/* __i2c_transfer returns the number of successfully transferred
	 * messages.
	 * So rc should be greater than 0 here otherwise we have an error.
	 */
	if (rc <= 0)
		return -EIO;

	return 0;
}

static int iic_tpm_write_generic(u8 addr, u8 *buffer, size_t len,
				 unsigned int sleep_low,
				 unsigned int sleep_hi, u8 max_count)
{
	int rc = -EIO;
	int count;

	struct i2c_msg msg1 = {
		.addr = tpm_dev.client->addr,
		.len = len + 1,
		.buf = tpm_dev.buf
	};

	if (len > TPM_I2C_INFINEON_BUFSIZE)
		return -EINVAL;

	if (!tpm_dev.client->adapter->algo->master_xfer)
		return -EOPNOTSUPP;
	i2c_lock_bus(tpm_dev.client->adapter, I2C_LOCK_SEGMENT);

	/* prepend the 'register address' to the buffer */
	tpm_dev.buf[0] = addr;
	memcpy(&(tpm_dev.buf[1]), buffer, len);

	/*
	 * NOTE: We have to use these special mechanisms here and unfortunately
	 * cannot rely on the standard behavior of i2c_transfer.
	 * Even for newer chips the smbus functions are not
	 * suitable due to the 32 byte limit of the smbus.
	 */
	for (count = 0; count < max_count; count++) {
		rc = __i2c_transfer(tpm_dev.client->adapter, &msg1, 1);
		if (rc > 0)
			break;
		usleep_range(sleep_low, sleep_hi);
	}

	i2c_unlock_bus(tpm_dev.client->adapter, I2C_LOCK_SEGMENT);
	/* take care of 'guard time' */
	usleep_range(SLEEP_DURATION_LOW, SLEEP_DURATION_HI);

	/* __i2c_transfer returns the number of successfully transferred
	 * messages.
	 * So rc