Merge tag 'tpmdd-next-v5.12-rc1-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd

Pull tpm updates from Jarkko Sakkinen:
 "New features:

   - Cr50 I2C TPM driver

   - sysfs exports of PCR registers in TPM 2.0 chips

  Bug fixes:

   - bug fixes for tpm_tis driver, which had a racy wait for hardware
     state change to be ready to send a command to the TPM chip. The bug
     has existed already since 2006, but has only made itself known in
     recent past. This is the same as the "last time" :-)

   - Otherwise there's bunch of fixes for not as alarming regressions. I
     think the list is about the same as last time, except I added fixes
     for some disjoint bugs in trusted keys that I found some time ago"

* tag 'tpmdd-next-v5.12-rc1-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd:
  KEYS: trusted: Reserve TPM for seal and unseal operations
  KEYS: trusted: Fix migratable=1 failing
  KEYS: trusted: Fix incorrect handling of tpm_get_random()
  tpm/ppi: Constify static struct attribute_group
  ABI: add sysfs description for tpm exports of PCR registers
  tpm: add sysfs exports for all banks of PCR registers
  keys: Update comment for restrict_link_by_key_or_keyring_chain
  tpm: Remove tpm_dev_wq_lock
  char: tpm: add i2c driver for cr50
  tpm: Fix fall-through warnings for Clang
  tpm_tis: Clean up locality release
  tpm_tis: Fix check_locality for correct locality acquisition

10 files changed, 988 insertions, 53 deletions

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index a18c314da211..4308f9ca7a43 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -86,6 +86,16 @@ config TCG_TIS_SYNQUACER
 	  To compile this driver as a module, choose  M here;
 	  the module will be called tpm_tis_synquacer.
 
+config TCG_TIS_I2C_CR50
+	tristate "TPM Interface Specification 2.0 Interface (I2C - CR50)"
+	depends on I2C
+	select TCG_CR50
+	help
+	  This is a driver for the Google cr50 I2C TPM interface which is a
+	  custom microcontroller and requires a custom i2c protocol interface
+	  to handle the limitations of the hardware.  To compile this driver
+	  as a module, choose M here; the module will be called tcg_tis_i2c_cr50.
+
 config TCG_TIS_I2C_ATMEL
 	tristate "TPM Interface Specification 1.2 Interface (I2C - Atmel)"
 	depends on I2C
diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index 84db4fb3a9c9..66d39ea6bd10 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -27,6 +27,8 @@ obj-$(CONFIG_TCG_TIS_SPI) += tpm_tis_spi.o
 tpm_tis_spi-y := tpm_tis_spi_main.o
 tpm_tis_spi-$(CONFIG_TCG_TIS_SPI_CR50) += tpm_tis_spi_cr50.o
 
+obj-$(CONFIG_TCG_TIS_I2C_CR50) += tpm_tis_i2c_cr50.o
+
 obj-$(CONFIG_TCG_TIS_I2C_ATMEL) += tpm_i2c_atmel.o
 obj-$(CONFIG_TCG_TIS_I2C_INFINEON) += tpm_i2c_infineon.o
 obj-$(CONFIG_TCG_TIS_I2C_NUVOTON) += tpm_i2c_nuvoton.o
diff --git a/drivers/char/tpm/eventlog/tpm1.c b/drivers/char/tpm/eventlog/tpm1.c
index 2c96977ad080..8aa9057601d6 100644
--- a/drivers/char/tpm/eventlog/tpm1.c
+++ b/drivers/char/tpm/eventlog/tpm1.c
@@ -210,6 +210,7 @@ static int get_event_name(char *dest, struct tcpa_event *event,
 		default:
 			break;
 		}
+		break;
 	default:
 		break;
 	}
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index ddaeceb7e109..19e23fcc6bc8 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -278,6 +278,8 @@ static void tpm_devs_release(struct device *dev)
 {
 	struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
 
+	dump_stack();
+
 	/* release the master device reference */
 	put_device(&chip->dev);
 }
diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
index 1784530b8387..c08cbb306636 100644
--- a/drivers/char/tpm/tpm-dev-common.c
+++ b/drivers/char/tpm/tpm-dev-common.c
@@ -20,7 +20,6 @@
 #include "tpm-dev.h"
 
 static struct workqueue_struct *tpm_dev_wq;
-static DEFINE_MUTEX(tpm_dev_wq_lock);
 
 static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
 				u8 *buf, size_t bufsiz)
diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index e2ff0b273a0f..63f03cfb8e6a 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -337,11 +337,190 @@ static const struct attribute_group tpm2_dev_group = {
 	.attrs = tpm2_dev_attrs,
 };
 
+struct tpm_pcr_attr {
+	int alg_id;
+	int pcr;
+	struct device_attribute attr;
+};
+
+#define to_tpm_pcr_attr(a) container_of(a, struct tpm_pcr_attr, attr)
+
+static ssize_t pcr_value_show(struct device *dev,
+			      struct device_attribute *attr,
+			      char *buf)
+{
+	struct tpm_pcr_attr *ha = to_tpm_pcr_attr(attr);
+	struct tpm_chip *chip = to_tpm_chip(dev);
+	struct tpm_digest digest;
+	int i;
+	int digest_size = 0;
+	int rc;
+	char *str = buf;
+
+	for (i = 0; i < chip->nr_allocated_banks; i++)
+		if (ha->alg_id == chip->allocated_banks[i].alg_id)
+			digest_size = chip->allocated_banks[i].digest_size;
+	/* should never happen */
+	if (!digest_size)
+		return -EINVAL;
+
+	digest.alg_id = ha->alg_id;
+	rc = tpm_pcr_read(chip, ha->pcr, &digest);
+	if (rc)
+		return rc;
+	for (i = 0; i < digest_size; i++)
+		str += sprintf(str, "%02X", digest.digest[i]);
+	str += sprintf(str, "\n");
+
+	return str - buf;
+}
+
+/*
+ * The following set of defines represents all the magic to build
+ * the per hash attribute groups for displaying each bank of PCRs.
+ * The only slight problem with this approach is that every PCR is
+ * hard coded to be present, so you don't know if an PCR is missing
+ * until a cat of the file returns -EINVAL
+ *
+ * Also note you must ignore checkpatch warnings in this macro
+ * code. This is deep macro magic that checkpatch.pl doesn't
+ * understand.
+ */
+
+/* Note, this must match TPM2_PLATFORM_PCR which is fixed at 24. */
+#define _TPM_HELPER(_alg, _hash, F) \
+	F(_alg, _hash, 0)	    \
+	F(_alg, _hash, 1)	    \
+	F(_alg, _hash, 2)	    \
+	F(_alg, _hash, 3)	    \
+	F(_alg, _hash, 4)	    \
+	F(_alg, _hash, 5)	    \
+	F(_alg, _hash, 6)	    \
+	F(_alg, _hash, 7)	    \
+	F(_alg, _hash, 8)	    \
+	F(_alg, _hash, 9)	    \
+	F(_alg, _hash, 10)	    \
+	F(_alg, _hash, 11)	    \
+	F(_alg, _hash, 12)	    \
+	F(_alg, _hash, 13)	    \
+	F(_alg, _hash, 14)	    \
+	F(_alg, _hash, 15)	    \
+	F(_alg, _hash, 16)	    \
+	F(_alg, _hash, 17)	    \
+	F(_alg, _hash, 18)	    \
+	F(_alg, _hash, 19)	    \
+	F(_alg, _hash, 20)	    \
+	F(_alg, _hash, 21)	    \
+	F(_alg, _hash, 22)	    \
+	F(_alg, _hash, 23)
+
+/* ignore checkpatch warning about trailing ; in macro. */
+#define PCR_ATTR(_alg, _hash, _pcr)				   \
+	static struct tpm_pcr_attr dev_attr_pcr_##_hash##_##_pcr = {	\
+		.alg_id = _alg,					   \
+		.pcr = _pcr,					   \
+		.attr = {					   \
+			.attr = {				   \
+				.name = __stringify(_pcr),	   \
+				.mode = 0444			   \
+			},					   \
+			.show = pcr_value_show			   \
+		}						   \
+	};
+
+#define PCR_ATTRS(_alg, _hash)			\
+	_TPM_HELPER(_alg, _hash, PCR_ATTR)
+
+/* ignore checkpatch warning about trailing , in macro. */
+#define PCR_ATTR_VAL(_alg, _hash, _pcr)		\
+	&dev_attr_pcr_##_hash##_##_pcr.attr.attr,
+
+#define PCR_ATTR_GROUP_ARRAY(_alg, _hash)		       \
+	static struct attribute *pcr_group_attrs_##_hash[] = { \
+		_TPM_HELPER(_alg, _hash, PCR_ATTR_VAL)	       \
+		NULL					       \
+	}
+
+#define PCR_ATTR_GROUP(_alg, _hash)			    \
+	static struct attribute_group pcr_group_##_hash = { \
+		.name = "pcr-" __stringify(_hash),	    \
+		.attrs = pcr_group_attrs_##_hash	    \
+	}
+
+#define PCR_ATTR_BUILD(_alg, _hash)	   \
+	PCR_ATTRS(_alg, _hash)		   \
+	PCR_ATTR_GROUP_ARRAY(_alg, _hash); \
+	PCR_ATTR_GROUP(_alg, _hash)
+/*
+ * End of macro structure to build an attribute group containing 24
+ * PCR value files for each supported hash algorithm
+ */
+
+/*
+ * The next set of macros implements the cleverness for each hash to
+ * build a static attribute group called pcr_group_<hash> which can be
+ * added to chip->groups[].
+ *
+ * The first argument is the TPM algorithm id and the second is the
+ * hash used as both the suffix and the group name.  Note: the group
+ * name is a directory in the top level tpm class with the name
+ * pcr-<hash>, so it must not clash with any other names already
+ * in the sysfs directory.
+ */
+PCR_ATTR_BUILD(TPM_ALG_SHA1, sha1);
+PCR_ATTR_BUILD(TPM_ALG_SHA256, sha256);
+PCR_ATTR_BUILD(TPM_ALG_SHA384, sha384);
+PCR_ATTR_BUILD(TPM_ALG_SHA512, sha512);
+PCR_ATTR_BUILD(TPM_ALG_SM3_256, sm3);
+
+
 void tpm_sysfs_add_device(struct tpm_chip *chip)
 {
+	int i;
+
 	WARN_ON(chip->groups_cnt != 0);
+
 	if (chip->flags & TPM_CHIP_FLAG_TPM2)
 		chip->groups[chip->groups_cnt++] = &tpm2_dev_group;
 	else
 		chip->groups[chip->groups_cnt++] = &tpm1_dev_group;
+
+	/* add one group for each bank hash */
+	for (i = 0; i < chip->nr_allocated_banks; i++) {
+		switch (chip->allocated_banks[i].alg_id) {
+		case TPM_ALG_SHA1:
+			chip->groups[chip->groups_cnt++] = &pcr_group_sha1;
+			break;
+		case TPM_ALG_SHA256:
+			chip->groups[chip->groups_cnt++] = &pcr_group_sha256;
+			break;
+		case TPM_ALG_SHA384:
+			chip->groups[chip->groups_cnt++] = &pcr_group_sha384;
+			break;
+		case TPM_ALG_SHA512:
+			chip->groups[chip->groups_cnt++] = &pcr_group_sha512;
+			break;
+		case TPM_ALG_SM3_256:
+			chip->groups[chip->groups_cnt++] = &pcr_group_sm3;
+			break;
+		default:
+			/*
+			 * If triggers, send a patch to add both a
+			 * PCR_ATTR_BUILD() macro above for the
+			 * missing algorithm as well as an additional
+			 * case in this switch statement.
+			 */
+			dev_err(&chip->dev,
+				"TPM with unsupported bank algorithm 0x%04x",
+				chip->allocated_banks[i].alg_id);
+			break;
+		}
+	}
+
+	/*
+	 * This will only trigger if someone has added an additional
+	 * hash to the tpm_algorithms enum without incrementing
+	 * TPM_MAX_HASHES.
+	 */
+	WARN_ON(chip->groups_cnt > TPM_MAX_HASHES + 1);
 }
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 947d1db0a5cc..283f78211c3a 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -164,8 +164,6 @@ extern const struct file_operations tpmrm_fops;
 extern struct idr dev_nums_idr;
 
 ssize_t tpm_transmit(struct tpm_chip *chip, u8 *buf, size_t bufsiz);
-ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_buf *buf,
-			 size_t min_rsp_body_length, const char *desc);
 int tpm_get_timeouts(struct tpm_chip *);
 int tpm_auto_startup(struct tpm_chip *chip);
 
@@ -194,8 +192,6 @@ static inline void tpm_msleep(unsigned int delay_msec)
 int tpm_chip_start(struct tpm_chip *chip);
 void tpm_chip_stop(struct tpm_chip *chip);
 struct tpm_chip *tpm_find_get_ops(struct tpm_chip *chip);
-__must_check int tpm_try_get_ops(struct tpm_chip *chip);
-void tpm_put_ops(struct tpm_chip *chip);
 
 struct tpm_chip *tpm_chip_alloc(struct device *dev,
 				const struct tpm_class_ops *ops);
diff --git a/drivers/char/tpm/tpm_ppi.c b/drivers/char/tpm/tpm_ppi.c
index b2dab941cb7f..40018a73b3cb 100644
--- a/drivers/char/tpm/tpm_ppi.c
+++ b/drivers/char/tpm/tpm_ppi.c
@@ -358,7 +358,7 @@ static struct attribute *ppi_attrs[] = {
 	&dev_attr_tcg_operations.attr,
 	&dev_attr_vs_operations.attr, NULL,
 };
-static struct attribute_group ppi_attr_grp = {
+static const struct attribute_group ppi_attr_grp = {
 	.name = "ppi",
 	.attrs = ppi_attrs
 };
diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 92c51c6cfd1b..431919d5f48a 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -125,7 +125,8 @@ static bool check_locality(struct tpm_chip *chip, int l)
 	if (rc < 0)
 		return false;
 
-	if ((access & (TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID)) ==
+	if ((access & (TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID
+		       | TPM_ACCESS_REQUEST_USE)) ==
 	    (TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID)) {
 		priv->locality = l;
 		return true;
@@ -134,58 +135,13 @@ static bool check_locality(struct tpm_chip *chip, int l)
 	return false;
 }
 
-static bool locality_inactive(struct tpm_chip *chip, int l)
-{
-	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
-	int rc;
-	u8 access;
-
-	rc = tpm_tis_read8(priv, TPM_ACCESS(l), &access);
-	if (rc < 0)
-		return false;
-
-	if ((access & (TPM_ACCESS_VALID | TPM_ACCESS_ACTIVE_LOCALITY))
-	    == TPM_ACCESS_VALID)
-		return true;
-
-	return false;
-}
-
 static int release_locality(struct tpm_chip *chip, int l)
 {
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
-	unsigned long stop, timeout;
-	long rc;
 
 	tpm_tis_write8(priv, TPM_ACCESS(l), TPM_ACCESS_ACTIVE_LOCALITY);
 
-	stop = jiffies + chip->timeout_a;
-
-	if (chip->flags & TPM_CHIP_FLAG_IRQ) {
-again:
-		timeout = stop - jiffies;
-		if ((long)timeout <= 0)
-			return -1;
-
-		rc = wait_event_interruptible_timeout(priv->int_queue,
-						      (locality_inactive(chip, l)),
-						      timeout);
-
-		if (rc > 0)
-			return 0;
-
-		if (rc == -ERESTARTSYS && freezing(current)) {
-			clear_thread_flag(TIF_SIGPENDING);
-			goto again;
-		}
-	} else {
-		do {
-			if (locality_inactive(chip, l))
-				return 0;
-			tpm_msleep(TPM_TIMEOUT);
-		} while (time_before(jiffies, stop));
-	}
-	return -1;
+	return 0;
 }
 
 static int request_locality(struct tpm_chip *chip, int l)
diff --git a/drivers/char/tpm/tpm_tis_i2c_cr50.c b/drivers/char/tpm/tpm_tis_i2c_cr50.c
new file mode 100644
index 000000000000..ec9a65e7887d
--- /dev/null
+++ b/drivers/char/tpm/tpm_tis_i2c_cr50.c
@@ -0,0 +1,790 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2020 Google Inc.
+ *
+ * Based on Infineon TPM driver by Peter Huewe.
+ *
+ * cr50 is a firmware for H1 secure modules that requires special
+ * handling for the I2C interface.
+ *
+ * - Use an interrupt for transaction status instead of hardcoded delays.
+ * - Must use write+wait+read read protocol.
+ * - All 4 bytes of status register must be read/written at once.
+ * - Burst count max is 63 bytes, and burst count behaves slightly differently
+ *   than other I2C TPMs.
+ * - When reading from FIFO the full burstcnt must be read instead of just
+ *   reading header and determining the remainder.
+ */
+
+#include <linux/acpi.h>
+#include <linux/completion.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/pm.h>
+#include <linux/slab.h>
+#include <linux/wait.h>
+
+#include "tpm_tis_core.h"
+
+#define TPM_CR50_MAX_BUFSIZE		64
+#define TPM_CR50_TIMEOUT_SHORT_MS	2		/* Short timeout during transactions */
+#define TPM_CR50_TIMEOUT_NOIRQ_MS	20		/* Timeout for TPM ready without IRQ */
+#define TPM_CR50_I2C_DID_VID		0x00281ae0L	/* Device and vendor ID reg value */
+#define TPM_CR50_I2C_MAX_RETRIES	3		/* Max retries due to I2C errors */
+#define TPM_CR50_I2C_RETRY_DELAY_LO	55		/* Min usecs between retries on I2C */
+#define TPM_CR50_I2C_RETRY_DELAY_HI	65		/* Max usecs between retries on I2C */
+
+#define TPM_I2C_ACCESS(l)	(0x0000 | ((l) << 4))
+#define TPM_I2C_STS(l)		(0x0001 | ((l) << 4))
+#define TPM_I2C_DATA_FIFO(l)	(0x0005 | ((l) << 4))
+#define TPM_I2C_DID_VID(l)	(0x0006 | ((l) << 4))
+
+/**
+ * struct tpm_i2c_cr50_priv_data - Driver private data.
+ * @irq:	Irq number used for this chip.
+ *		If irq <= 0, then a fixed timeout is used instead of waiting for irq.
+ * @tpm_ready:	Struct used by irq handler to signal R/W readiness.
+ * @buf:	Buffer used for i2c writes, with i2c address prepended to content.
+ *
+ * Private driver struct used by kernel threads and interrupt context.
+ */
+struct tpm_i2c_cr50_priv_data {
+	int irq;
+	struct completion tpm_ready;
+	u8 buf[TPM_CR50_MAX_BUFSIZE];
+};
+
+/**
+ * tpm_cr50_i2c_int_handler() - cr50 interrupt handler.
+ * @dummy:	Unused parameter.
+ * @tpm_info:	TPM chip information.
+ *
+ * The cr50 interrupt handler signals waiting threads that the
+ * interrupt has been asserted. It does not do any interrupt triggered
+ * processing but is instead used to avoid fixed delays.
+ *
+ * Return:
+ *	IRQ_HANDLED signifies irq was handled by this device.
+ */
+static irqreturn_t tpm_cr50_i2c_int_handler(int dummy, void *tpm_info)
+{
+	struct tpm_chip *chip = tpm_info;
+	struct tpm_i2c_cr50_priv_data *priv = dev_get_drvdata(&chip->dev);
+
+	complete(&priv->tpm_ready);
+
+	return IRQ_HANDLED;
+}
+
+/**
+ * tpm_cr50_i2c_wait_tpm_ready() - Wait for tpm to signal ready.
+ * @chip: A TPM chip.
+ *
+ * Wait for completion interrupt if available, otherwise use a fixed
+ * delay for the TPM to be ready.
+ *
+ * Return:
+ * - 0:		Success.
+ * - -errno:	A POSIX error code.
+ */
+static int tpm_cr50_i2c_wait_tpm_ready(struct tpm_chip *chip)
+{
+	struct tpm_i2c_cr50_priv_data *priv = dev_get_drvdata(&chip->dev);
+
+	/* Use a safe fixed delay if interrupt is not supported */
+	if (priv->irq <= 0) {
+		msleep(TPM_CR50_TIMEOUT_NOIRQ_MS);
+		return 0;
+	}
+
+	/* Wait for interrupt to indicate TPM is ready to respond */
+	if (!wait_for_completion_timeout(&priv->tpm_ready,
+					 msecs_to_jiffies(chip->timeout_a))) {
+		dev_warn(&chip->dev, "Timeout waiting for TPM ready\n");
+		return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+
+/**
+ * tpm_cr50_i2c_enable_tpm_irq() - Enable TPM irq.
+ * @chip: A TPM chip.
+ */
+static void tpm_cr50_i2c_enable_tpm_irq(struct tpm_chip *chip)
+{
+	struct tpm_i2c_cr50_priv_data *priv = dev_get_drvdata(&chip->dev);
+
+	if (priv->irq > 0) {
+		reinit_completion(&priv->tpm_ready);
+		enable_irq(priv->irq);
+	}
+}
+
+/**
+ * tpm_cr50_i2c_disable_tpm_irq() - Disable TPM irq.
+ * @chip: A TPM chip.
+ */
+static void tpm_cr50_i2c_disable_tpm_irq(struct tpm_chip *chip)
+{
+	struct tpm_i2c_cr50_priv_data *priv = dev_get_drvdata(&chip->dev);
+
+	if (priv->irq > 0)
+		disable_irq(priv->irq);
+}
+
+/**
+ * tpm_cr50_i2c_transfer_message() - Transfer a message over i2c.
+ * @dev:	Device information.
+ * @adapter:	I2C adapter.
+ * @msg:	Message to transfer.
+ *
+ * Call unlocked i2c transfer routine with the provided parameters and
+ * retry in case of bus errors.
+ *
+ * Return:
+ * - 0:		Success.
+ * - -errno:	A POSIX error code.
+ */
+static int tpm_cr50_i2c_transfer_message(struct device *dev,
+					 struct i2c_adapter *adapter,
+					 struct i2c_msg *msg)
+{
+	unsigned int try;
+	int rc;
+
+	for (try = 0; try < TPM_CR50_I2C_MAX_RETRIES; try++) {
+		rc = __i2c_transfer(adapter, msg, 1);
+		if (rc == 1)
+			return 0; /* Successfully transferred the message */
+		if (try)
+			dev_warn(dev, "i2c transfer failed (attempt %d/%d): %d\n",
+				 try + 1, TPM_CR50_I2C_MAX_RETRIES, rc);
+		usleep_range(TPM_CR50_I2C_RETRY_DELAY_LO, TPM_CR50_I2C_RETRY_DELAY_HI);
+	}
+
+	/* No i2c message transferred */
+	return -EIO;
+}
+
+/**
+ * tpm_cr50_i2c_read() - Read from TPM register.
+ * @chip:	A TPM chip.
+ * @addr:	Register address to read from.
+ * @buffer:	Read destination, provided by caller.
+ * @len:	Number of bytes to read.
+ *
+ * Sends the register address byte to the TPM, then waits until TPM
+ * is ready via interrupt signal or timeout expiration, then 'len'
+ * bytes are read from TPM response into the provided 'buffer'.
+ *
+ * Return:
+ * - 0:		Success.
+ * - -errno:	A POSIX error code.
+ */
+static int tpm_cr50_i2c_read(struct tpm_chip *chip, u8 addr, u8 *buffer, size_t len)
+{
+	struct i2c_client *client = to_i2c_client(chip->dev.parent);
+	struct i2c_msg msg_reg_addr = {
+		.addr = client->addr,
+		.len = 1,
+		.buf = &addr
+	};
+	struct i2c_msg msg_response = {
+		.addr = client->addr,
+		.flags = I2C_M_RD,
+		.len = len,
+		.buf = buffer
+	};
+	int rc;
+
+	i2c_lock_bus(client->adapter, I2C_LOCK_SEGMENT);
+
+	/* Prepare for completion interrupt */
+	tpm_cr50_i2c_enable_tpm_irq(chip);
+
+	/* Send the register address byte to the TPM */
+	rc = tpm_cr50_i2c_transfer_message(&chip->dev, client->adapter, &msg_reg_addr);
+	if (rc < 0)
+		goto out;
+
+	/* Wait for TPM to be ready with response data */
+	rc = tpm_cr50_i2c_wait_tpm_ready(chip);
+	if (rc < 0)
+		goto out;
+
+	/* Read response data from the TPM */
+	rc = tpm_cr50_i2c_transfer_message(&chip->dev, client->adapter, &msg_response);
+
+out:
+	tpm_cr50_i2c_disable_tpm_irq(chip);
+	i2c_unlock_bus(client->adapter, I2C_LOCK_SEGMENT);
+
+	if (rc < 0)
+		return rc;
+
+	return 0;
+}
+
+/**
+ * tpm_cr50_i2c_write()- Write to TPM register.
+ * @chip:	A TPM chip.
+ * @addr:	Register address to write to.
+ * @buffer:	Data to write.
+ * @len:	Number of bytes to write.
+ *
+ * The provided address is prepended to the data in 'buffer', the
+ * cobined address+data is sent to the TPM, then wait for TPM to
+ * indicate it is done writing.
+ *
+ * Return:
+ * - 0:		Success.
+ * - -errno:	A POSIX error code.
+ */
+static int tpm_cr50_i2c_write(struct tpm_chip *chip, u8 addr, u8 *buffer,
+			      size_t len)
+{
+	struct tpm_i2c_cr50_priv_data *priv = dev_get_drvdata(&chip->dev);
+	struct i2c_client *client = to_i2c_client(chip->dev.parent);
+	struct i2c_msg msg = {
+		.addr = client->addr,
+		.len = len + 1,
+		.buf = priv->buf
+	};
+	int rc;
+
+	if (len > TPM_CR50_MAX_BUFSIZE - 1)
+		return -EINVAL;
+
+	/* Prepend the 'register address' to the buffer */
+	priv->buf[0] = addr;
+	memcpy(priv->buf + 1, buffer, len);
+
+	i2c_lock_bus(client->adapter, I2C_LOCK_SEGMENT);
+
+	/* Prepare for completion interrupt */
+	tpm_cr50_i2c_enable_tpm_irq(chip);
+
+	/* Send write request buffer with address */
+	rc = tpm_cr50_i2c_transfer_message(&chip->dev, client->adapter, &msg);
+	if (rc < 0)
+		goto out;
+
+	/* Wait for TPM to be ready, ignore timeout */
+	tpm_cr50_i2c_wait_tpm_ready(chip);
+
+out:
+	tpm_cr50_i2c_disable_tpm_irq(chip);
+	i2c_unlock_bus(client->adapter, I2C_LOCK_SEGMENT);
+
+	if (rc < 0)
+		return rc;
+
+	return 0;
+}
+
+/**
+ * tpm_cr50_check_locality() - Verify TPM locality 0 is active.
+ * @chip: A TPM chip.
+ *
+ * Return:
+ * - 0:		Success.
+ * - -errno:	A POSIX error code.
+ */
+static int tpm_cr50_check_locality(struct tpm_chip *chip)
+{
+	u8 mask = TPM_ACCESS_VALID | TPM_ACCESS_ACTIVE_LOCALITY;
+	u8 buf;
+	int rc;
+
+	rc = tpm_cr50_i2c_read(chip, TPM_I2C_ACCESS(0), &buf, sizeof(buf));
+	if (rc < 0)
+		return rc;
+
+	if ((buf & mask) == mask)
+		return 0;
+
+	return -EIO;
+}
+
+/**
+ * tpm_cr50_release_locality() - Release TPM locality.
+ * @chip:	A TPM chip.
+ * @force:	Flag to force release if set.
+ */
+static void tpm_cr50_release_locality(struct tpm_chip *chip, bool force)
+{
+	u8 mask = TPM_ACCESS_VALID | TPM_ACCESS_REQUEST_PENDING;
+	u8 addr = TPM_I2C_ACCESS(0);
+	u8 buf;
+
+	if (tpm_cr50_i2c_read(chip, addr, &buf, sizeof(buf)) < 0)
+		return;
+
+	if (force || (buf & mask) == mask) {
+		buf = TPM_ACCESS_ACTIVE_LOCALITY;
+		tpm_cr50_i2c_write(chip, addr, &buf, sizeof(buf));
+	}
+}
+
+/**
+ * tpm_cr50_request_locality() - Request TPM locality 0.
+ * @chip: A TPM chip.
+ *
+ * Return:
+ * - 0:		Success.
+ * - -errno:	A POSIX error code.
+ */
+static int tpm_cr50_request_locality(struct tpm_chip *chip)
+{
+	u8 buf = TPM_ACCESS_REQUEST_USE;
+	unsigned long stop;
+	int rc;
+
+	if (!tpm_cr50_check_locality(chip))
+		return 0;
+
+	rc = tpm_cr50_i2c_write(chip, TPM_I2C_ACCESS(0), &buf, sizeof(buf));
+	if (rc < 0)
+		return rc;
+
+	stop = jiffies + chip->timeout_a;
+	do {
+		if (!tpm_cr50_check_locality(chip))
+			return 0;
+
+		msleep(TPM_CR50_TIMEOUT_SHORT_MS);
+	} while (time_before(jiffies, stop));
+
+	return -ETIMEDOUT;
+}
+
+/**
+ * tpm_cr50_i2c_tis_status() - Read cr50 tis status.
+ * @chip: A TPM chip.
+ *
+ * cr50 requires all 4 bytes of status register to be read.
+ *
+ * Return:
+ *	TPM status byte.
+ */
+static u8 tpm_cr50_i2c_tis_status(struct tpm_chip *chip)
+{
+	u8 buf[4];
+
+	if (tpm_cr50_i2c_read(chip, TPM_I2C_STS(0), buf, sizeof(buf)) < 0)
+		return 0;
+
+	return buf[0];
+}
+
+/**
+ * tpm_cr50_i2c_tis_set_ready() - Set status register to ready.
+ * @chip: A TPM chip.
+ *
+ * cr50 requires all 4 bytes of status register to be written.
+ */
+static void tpm_cr50_i2c_tis_set_ready(struct tpm_chip *chip)
+{
+	u8 buf[4] = { TPM_STS_COMMAND_READY };
+
+	tpm_cr50_i2c_write(chip, TPM_I2C_STS(0), buf, sizeof(buf));
+	msleep(TPM_CR50_TIMEOUT_SHORT_MS);
+}
+
+/**
+ * tpm_cr50_i2c_get_burst_and_status() - Get burst count and status.
+ * @chip:	A TPM chip.
+ * @mask:	Status mask.
+ * @burst:	Return value for burst.
+ * @status:	Return value for status.
+ *
+ * cr50 uses bytes 3:2 of status register for burst count and
+ * all 4 bytes must be read.
+ *
+ * Return:
+ * - 0:		Success.
+ * - -errno:	A POSIX error code.
+ */
+static int tpm_cr50_i2c_get_burst_and_status(struct tpm_chip *chip, u8 mask,
+					     size_t *burst, u32 *status)
+{
+	unsigned long stop;
+	u8 buf[4];
+
+	*status = 0;
+
+	/* wait for burstcount */
+	stop = jiffies + chip->timeout_b;
+
+	do {
+		if (tpm_cr50_i2c_read(chip, TPM_I2C_STS(0), buf, sizeof(buf)) < 0) {
+			msleep(TPM_CR50_TIMEOUT_SHORT_MS);
+			continue;
+		}
+
+		*status = *buf;
+		*burst = le16_to_cpup((__le16 *)(buf + 1));
+
+		if ((*status & mask) == mask &&
+		    *burst > 0 && *burst <= TPM_CR50_MAX_BUFSIZE - 1)
+			return 0;
+
+		msleep(TPM_CR50_TIMEOUT_SHORT_MS);
+	} while (time_before(jiffies, stop));
+
+	dev_err(&chip->dev, "Timeout reading burst and status\n");
+	return -ETIMEDOUT;
+}
+
+/**
+ * tpm_cr50_i2c_tis_recv() - TPM reception callback.
+ * @chip:	A TPM chip.
+ * @buf:	Reception buffer.
+ * @buf_len:	Buffer length to read.
+ *
+ * Return:
+ * - >= 0:	Number of read bytes.
+ * - -errno:	A POSIX error code.
+ */
+static int tpm_cr50_i2c_tis_recv(struct tpm_chip *chip, u8 *buf, size_t buf_len)
+{
+
+	u8 mask = TPM_STS_VALID | TPM_STS_DATA_AVAIL;
+	size_t burstcnt, cur, len, expected;
+	u8 addr = TPM_I2C_DATA_FIFO(0);
+	u32 status;
+	int rc;
+
+	if (buf_len < TPM_HEADER_SIZE)
+		return -EINVAL;
+
+	rc = tpm_cr50_i2c_get_burst_and_status(chip, mask, &burstcnt, &status);
+	if (rc < 0)
+		goto out_err;
+
+	if (burstcnt > buf_len || burstcnt < TPM_HEADER_SIZE) {
+		dev_err(&chip->dev,
+			"Unexpected burstcnt: %zu (max=%zu, min=%d)\n",
+			burstcnt, buf_len, TPM_HEADER_SIZE);
+		rc = -EIO;
+		goto out_err;
+	}
+
+	/* Read first chunk of burstcnt bytes */
+	rc = tpm_cr50_i2c_read(chip, addr, buf, burstcnt);
+	if (rc < 0) {
+		dev_err(&chip->dev, "Read of first chunk failed\n");
+		goto out_err;
+	}
+
+	/* Determine expected data in the return buffer */
+	expected = be32_to_cpup((__be32 *)(buf + 2));
+	if (expected > buf_len) {
+		dev_err(&chip->dev, "Buffer too small to receive i2c data\n");
+		goto out_err;
+	}
+
+	/* Now read the rest of the data */
+	cur = burstcnt;
+	while (cur < expected) {
+		/* Read updated burst count and check status */
+		rc = tpm_cr50_i2c_get_burst_and_status(chip, mask, &burstcnt, &status);
+		if (rc < 0)
+			goto out_err;
+
+		len = min_t(size_t, burstcnt, expected - cur);
+		rc = tpm_cr50_i2c_read(chip, addr, buf + cur, len);
+		if (rc < 0) {
+			dev_err(&chip->dev, "Read failed\n");
+			goto out_err;
+		}
+
+		cur += len;
+	}
+
+	/* Ensure TPM is done reading data */
+	rc = tpm_cr50_i2c_get_burst_and_status(chip, TPM_STS_VALID, &burstcnt, &status);
+	if (rc < 0)
+		goto out_err;
+	if (status & TPM_STS_DATA_AVAIL) {
+		dev_err(&chip->dev, "Data still available\n");
+		rc = -EIO;
+		goto out_err;
+	}
+
+	tpm_cr50_release_locality(chip, false);
+	return cur;
+
+out_err:
+	/* Abort current transaction if still pending */
+	if (tpm_cr50_i2c_tis_status(chip) & TPM_STS_COMMAND_READY)
+		tpm_cr50_i2c_tis_set_ready(chip);
+
+	tpm_cr50_release_locality(chip, false);
+	return rc;
+}
+
+/**
+ * tpm_cr50_i2c_tis_send() - TPM transmission callback.
+ * @chip:	A TPM chip.
+ * @buf:	Buffer to send.
+ * @len:	Buffer length.
+ *
+ * Return:
+ * - 0:		Success.
+ * - -errno:	A POSIX error code.
+ */
+static int tpm_cr50_i2c_tis_send(struct tpm_chip *chip, u8 *buf, size_t len)
+{
+	size_t burstcnt, limit, sent = 0;
+	u8 tpm_go[4] = { TPM_STS_GO };
+	unsigned long stop;
+	u32 status;
+	int rc;
+
+	rc = tpm_cr50_request_locality(chip);
+	if (rc < 0)
+		return rc;
+
+	/* Wait until TPM is ready for a command */
+	stop = jiffies + chip->timeout_b;
+	while (!(tpm_cr50_i2c_tis_status(chip) & TPM_STS_COMMAND_READY)) {
+		if (time_after(jiffies, stop)) {
+			rc = -ETIMEDOUT;
+			goto out_err;
+		}
+
+		tpm_cr50_i2c_tis_set_ready(chip);
+	}
+
+	while (len > 0) {
+		u8 mask = TPM_STS_VALID;
+
+		/* Wait for data if this is not the first chunk */
+		if (sent > 0)
+			mask |= TPM_STS_DATA_EXPECT;
+
+		/* Read burst count and check status */
+		rc = tpm_cr50_i2c_get_burst_and_status(chip, mask, &burstcnt, &status);
+		if (rc < 0)
+			goto out_err;
+
+		/*
+		 * Use burstcnt - 1 to account for the address byte
+		 * that is inserted by tpm_cr50_i2c_write()
+		 */
+		limit = min_t(size_t, burstcnt - 1, len);
+		rc = tpm_cr50_i2c_write(chip, TPM_I2C_DATA_FIFO(0), &buf[sent], limit);
+		if (rc < 0) {
+			dev_err(&chip->dev, "Write failed\n");
+			goto out_err;
+		}
+
+		sent += limit;
+		len -= limit;
+	}
+
+	/* Ensure TPM is not expecting more data */
+	rc = tpm_cr50_i2c_get_burst_and_status(chip, TPM_STS_VALID, &burstcnt, &status);
+	if (rc < 0)
+		goto out_err;
+	if (status & TPM_STS_DATA_EXPECT) {
+		dev_err(&chip->dev, "Data still expected\n");
+		rc = -EIO;
+		goto out_err;
+	}
+
+	/* Start the TPM command */
+	rc = tpm_cr50_i2c_write(chip, TPM_I2C_STS(0), tpm_go,
+				sizeof(tpm_go));
+	if (rc < 0) {
+		dev_err(&chip->dev, "Start command failed\n");
+		goto out_err;
+	}
+	return 0;
+
+out_err:
+	/* Abort current transaction if still pending */
+	if (tpm_cr50_i2c_tis_status(chip) & TPM_STS_COMMAND_READY)
+		tpm_cr50_i2c_tis_set_ready(chip);
+
+	tpm_cr50_release_locality(chip, false);
+	return rc;
+}
+
+/**
+ * tpm_cr50_i2c_req_canceled() - Callback to notify a request cancel.
+ * @chip:	A TPM chip.
+ * @status:	Status given by the cancel callback.
+ *
+ * Return:
+ *	True if command is ready, False otherwise.
+ */
+static bool tpm_cr50_i2c_req_canceled(struct tpm_chip *chip, u8 status)
+{
+	return status == TPM_STS_COMMAND_READY;
+}
+
+static const struct tpm_class_ops cr50_i2c = {
+	.flags = TPM_OPS_AUTO_STARTUP,
+	.status = &tpm_cr50_i2c_tis_status,
+	.recv = &tpm_cr50_i2c_tis_recv,
+	.send = &tpm_cr50_i2c_tis_send,
+	.cancel = &tpm_cr50_i2c_tis_set_ready,
+	.req_complete_mask = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
+	.req_complete_val = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
+	.req_canceled = &tpm_cr50_i2c_req_canceled,
+};
+
+static const struct i2c_device_id cr50_i2c_table[] = {
+	{"cr50_i2c", 0},
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, cr50_i2c_table);
+
+#ifdef CONFIG_ACPI
+static const struct acpi_device_id cr50_i2c_acpi_id[] = {
+	{ "GOOG0005", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(acpi, cr50_i2c_acpi_id);
+#endif
+
+#ifdef CONFIG_OF
+static const struct of_device_id of_cr50_i2c_match[] = {
+	{ .compatible = "google,cr50", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, of_cr50_i2c_match);
+#endif
+
+/**
+ * tpm_cr50_i2c_probe() - Driver probe function.
+ * @client:	I2C client information.
+ * @id:		I2C device id.
+ *
+ * Return:
+ * - 0:		Success.
+ * - -errno:	A POSIX error code.
+ */
+static int tpm_cr50_i2c_probe(struct i2c_client *client,
+			      const struct i2c_device_id *id)
+{
+	struct tpm_i2c_cr50_priv_data *priv;
+	struct device *dev = &client->dev;
+	struct tpm_chip *chip;
+	u32 vendor;
+	u8 buf[4];
+	int rc;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -ENODEV;
+
+	chip = tpmm_chip_alloc(dev, &cr50_i2c);
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	/* cr50 is a TPM 2.0 chip */
+	chip->flags |= TPM_CHIP_FLAG_TPM2;
+	chip->flags |= TPM_CHIP_FLAG_FIRMWARE_POWER_MANAGED;
+
+	/* Default timeouts */
+	chip->timeout_a = msecs_to_jiffies(TIS_SHORT_TIMEOUT);
+	chip->timeout_b = msecs_to_jiffies(TIS_LONG_TIMEOUT);
+	chip->timeout_c = msecs_to_jiffies(TIS_SHORT_TIMEOUT);
+	chip->timeout_d = msecs_to_jiffies(TIS_SHORT_TIMEOUT);
+
+	dev_set_drvdata(&chip->dev, priv);
+	init_completion(&priv->tpm_ready);
+
+	if (client->irq > 0) {
+		rc = devm_request_irq(dev, client->irq, tpm_cr50_i2c_int_handler,
+				      IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+				      dev->driver->name, chip);
+		if (rc < 0) {
+			dev_err(dev, "Failed to probe IRQ %d\n", client->irq);
+			return rc;
+		}
+
+		disable_irq(client->irq);
+		priv->irq = client->irq;
+	} else {
+		dev_warn(dev, "No IRQ, will use %ums delay for TPM ready\n",
+			 TPM_CR50_TIMEOUT_NOIRQ_MS);
+	}
+
+	rc = tpm_cr50_request_locality(chip);
+	if (rc < 0) {
+		dev_err(dev, "Could not request locality\n");
+		return rc;
+	}
+
+	/* Read four bytes from DID_VID register */
+	rc = tpm_cr50_i2c_read(chip, TPM_I2C_DID_VID(0), buf, sizeof(buf));
+	if (rc < 0) {
+		dev_err(dev, "Could not read vendor id\n");
+		tpm_cr50_release_locality(chip, true);
+		return rc;
+	}
+
+	vendor = le32_to_cpup((__le32 *)buf);
+	if (vendor != TPM_CR50_I2C_DID_VID) {
+		dev_err(dev, "Vendor ID did not match! ID was %08x\n", vendor);
+		tpm_cr50_release_locality(chip, true);
+		return -ENODEV;
+	}
+
+	dev_info(dev, "cr50 TPM 2.0 (i2c 0x%02x irq %d id 0x%x)\n",
+		 client->addr, client->irq, vendor >> 16);
+
+	return tpm_chip_register(chip);
+}
+
+/**
+ * tpm_cr50_i2c_remove() - Driver remove function.
+ * @client: I2C client information.
+ *
+ * Return:
+ * - 0:		Success.
+ * - -errno:	A POSIX error code.
+ */
+static int tpm_cr50_i2c_remove(struct i2c_client *client)
+{
+	struct tpm_chip *chip = i2c_get_clientdata(client);
+	struct device *dev = &client->dev;
+
+	if (!chip) {
+		dev_err(dev, "Could not get client data at remove\n");
+		return -ENODEV;
+	}
+
+	tpm_chip_unregister(chip);
+	tpm_cr50_release_locality(chip, true);
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(cr50_i2c_pm, tpm_pm_suspend, tpm_pm_resume);
+
+static struct i2c_driver cr50_i2c_driver = {
+	.id_table = cr50_i2c_table,
+	.probe = tpm_cr50_i2c_probe,
+	.remove = tpm_cr50_i2c_remove,
+	.driver = {
+		.name = "cr50_i2c",
+		.pm = &cr50_i2c_pm,
+		.acpi_match_table = ACPI_PTR(cr50_i2c_acpi_id),
+		.of_match_table = of_match_ptr(of_cr50_i2c_match),
+	},
+};
+
+module_i2c_driver(cr50_i2c_driver);
+
+MODULE_DESCRIPTION("cr50 TPM I2C Driver");
+MODULE_LICENSE("GPL");