tpm: Add support for the Nuvoton NPCT501 I2C TPM

This chip is/was also branded as a Winbond WPCT301.

Originally written by Dan Morav <dmorav@nuvoton.com> and posted to LKML:
https://lkml.org/lkml/2011/9/7/206

The original posting was not merged, I have taken it as a
starting point, forward ported, tested and revised the driver:
 - Rework interrupt handling to work properly with level triggered
   interrupts. The old version just locked up.
 - Synchronize various items with Peter Huewe's Infineon driver:
    * Add durations/timeouts sysfs calls
    * Remove I2C device auto-detection
    * Don't fiddle with chip->release
    * Call tpm_dev_vendor_release in the probe error path
    * Use MODULE_DEVICE_TABLE for the I2C ids
    * Provide OF compatible strings for DT support
    * Use SIMPLE_DEV_PM_OPS
    * Use module_i2c_driver
 - checkpatch cleanups
 - Testing on ARM Kirkwood with GPIO interrupts, with this device tree:
	tpm@57 {
                compatible = "nuvoton,npct501";
                reg = <0x57>;
                interrupt-parent = <&gpio1>;
                interrupts = <6 IRQ_TYPE_LEVEL_LOW>;
        };

Signed-off-by: Dan Morav <dmorav@nuvoton.com>
[jgg: revised and tested]
Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
[phuewe: minor whitespace changes, fixed module name in kconfig]

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>

3 files changed, 721 insertions, 0 deletions

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index 94c0c74434ea..ade71c134a1a 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -44,6 +44,16 @@ config TCG_TIS_I2C_INFINEON
 	  To compile this driver as a module, choose M here; the module
 	  will be called tpm_tis_i2c_infineon.
 
+config TCG_TIS_I2C_NUVOTON
+	tristate "TPM Interface Specification 1.2 Interface (I2C - Nuvoton)"
+	depends on I2C
+	---help---
+	  If you have a TPM security chip with an I2C interface from
+	  Nuvoton Technology Corp. say Yes and it will be accessible
+	  from within Linux.
+	  To compile this driver as a module, choose M here; the module
+	  will be called tpm_i2c_nuvoton.
+
 config TCG_NSC
 	tristate "National Semiconductor TPM Interface"
 	depends on X86
diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index 15df2f38ae42..07ee67cf3341 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -14,6 +14,7 @@ endif
 endif
 obj-$(CONFIG_TCG_TIS) += tpm_tis.o
 obj-$(CONFIG_TCG_TIS_I2C_INFINEON) += tpm_i2c_infineon.o
+obj-$(CONFIG_TCG_TIS_I2C_NUVOTON) += tpm_i2c_nuvoton.o
 obj-$(CONFIG_TCG_NSC) += tpm_nsc.o
 obj-$(CONFIG_TCG_ATMEL) += tpm_atmel.o
 obj-$(CONFIG_TCG_INFINEON) += tpm_infineon.o
diff --git a/drivers/char/tpm/tpm_i2c_nuvoton.c b/drivers/char/tpm/tpm_i2c_nuvoton.c
new file mode 100644
index 000000000000..6276fea01ff0
--- /dev/null
+++ b/drivers/char/tpm/tpm_i2c_nuvoton.c
@@ -0,0 +1,710 @@
+/******************************************************************************
+ * Nuvoton TPM I2C Device Driver Interface for WPCT301/NPCT501,
+ * based on the TCG TPM Interface Spec version 1.2.
+ * Specifications at www.trustedcomputinggroup.org
+ *
+ * Copyright (C) 2011, Nuvoton Technology Corporation.
+ *  Dan Morav <dan.morav@nuvoton.com>
+ * Copyright (C) 2013, Obsidian Research Corp.
+ *  Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
+ *
+ * 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, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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, see http://www.gnu.org/licenses/>.
+ *
+ * Nuvoton contact information: APC.Support@nuvoton.com
+ *****************************************************************************/
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/wait.h>
+#include <linux/i2c.h>
+#include "tpm.h"
+
+/* I2C interface offsets */
+#define TPM_STS                0x00
+#define TPM_BURST_COUNT        0x01
+#define TPM_DATA_FIFO_W        0x20
+#define TPM_DATA_FIFO_R        0x40
+#define TPM_VID_DID_RID        0x60
+/* TPM command header size */
+#define TPM_HEADER_SIZE        10
+#define TPM_RETRY      5
+/*
+ * I2C bus device maximum buffer size w/o counting I2C address or command
+ * i.e. max size required for I2C write is 34 = addr, command, 32 bytes data
+ */
+#define TPM_I2C_MAX_BUF_SIZE           32
+#define TPM_I2C_RETRY_COUNT            32
+#define TPM_I2C_BUS_DELAY              1       /* msec */
+#define TPM_I2C_RETRY_DELAY_SHORT      2       /* msec */
+#define TPM_I2C_RETRY_DELAY_LONG       10      /* msec */
+
+#define I2C_DRIVER_NAME "tpm_i2c_nuvoton"
+
+struct priv_data {
+	unsigned int intrs;
+};
+
+static s32 i2c_nuvoton_read_buf(struct i2c_client *client, u8 offset, u8 size,
+				u8 *data)
+{
+	s32 status;
+
+	status = i2c_smbus_read_i2c_block_data(client, offset, size, data);
+	dev_dbg(&client->dev,
+		"%s(offset=%u size=%u data=%*ph) -> sts=%d\n", __func__,
+		offset, size, (int)size, data, status);
+	return status;
+}
+
+static s32 i2c_nuvoton_write_buf(struct i2c_client *client, u8 offset, u8 size,
+				 u8 *data)
+{
+	s32 status;
+
+	status = i2c_smbus_write_i2c_block_data(client, offset, size, data);
+	dev_dbg(&client->dev,
+		"%s(offset=%u size=%u data=%*ph) -> sts=%d\n", __func__,
+		offset, size, (int)size, data, status);
+	return status;
+}
+
+#define TPM_STS_VALID          0x80
+#define TPM_STS_COMMAND_READY  0x40
+#define TPM_STS_GO             0x20
+#define TPM_STS_DATA_AVAIL     0x10
+#define TPM_STS_EXPECT         0x08
+#define TPM_STS_RESPONSE_RETRY 0x02
+#define TPM_STS_ERR_VAL        0x07    /* bit2...bit0 reads always 0 */
+
+#define TPM_I2C_SHORT_TIMEOUT  750     /* ms */
+#define TPM_I2C_LONG_TIMEOUT   2000    /* 2 sec */
+
+/* read TPM_STS register */
+static u8 i2c_nuvoton_read_status(struct tpm_chip *chip)
+{
+	struct i2c_client *client = to_i2c_client(chip->dev);
+	s32 status;
+	u8 data;
+
+	status = i2c_nuvoton_read_buf(client, TPM_STS, 1, &data);
+	if (status <= 0) {
+		dev_err(chip->dev, "%s() error return %d\n", __func__,
+			status);
+		data = TPM_STS_ERR_VAL;
+	}
+
+	return data;
+}
+
+/* write byte to TPM_STS register */
+static s32 i2c_nuvoton_write_status(struct i2c_client *client, u8 data)
+{
+	s32 status;
+	int i;
+
+	/* this causes the current command to be aborted */
+	for (i = 0, status = -1; i < TPM_I2C_RETRY_COUNT && status < 0; i++) {
+		status = i2c_nuvoton_write_buf(client, TPM_STS, 1, &data);
+		msleep(TPM_I2C_BUS_DELAY);
+	}
+	return status;
+}
+
+/* write commandReady to TPM_STS register */
+static void i2c_nuvoton_ready(struct tpm_chip *chip)
+{
+	struct i2c_client *client = to_i2c_client(chip->dev);
+	s32 status;
+
+	/* this causes the current command to be aborted */
+	status = i2c_nuvoton_write_status(client, TPM_STS_COMMAND_READY);
+	if (status < 0)
+		dev_err(chip->dev,
+			"%s() fail to write TPM_STS.commandReady\n", __func__);
+}
+
+/* read burstCount field from TPM_STS register
+ * return -1 on fail to read */
+static int i2c_nuvoton_get_burstcount(struct i2c_client *client,
+				      struct tpm_chip *chip)
+{
+	unsigned long stop = jiffies + chip->vendor.timeout_d;
+	s32 status;
+	int burst_count = -1;
+	u8 data;
+
+	/* wait for burstcount to be non-zero */
+	do {
+		/* in I2C burstCount is 1 byte */
+		status = i2c_nuvoton_read_buf(client, TPM_BURST_COUNT, 1,
+					      &data);
+		if (status > 0 && data > 0) {
+			burst_count = min_t(u8, TPM_I2C_MAX_BUF_SIZE, data);
+			break;
+		}
+		msleep(TPM_I2C_BUS_DELAY);
+	} while (time_before(jiffies, stop));
+
+	return burst_count;
+}
+
+/*
+ * WPCT301/NPCT501 SINT# supports only dataAvail
+ * any call to this function which is not waiting for dataAvail will
+ * set queue to NULL to avoid waiting for interrupt
+ */
+static bool i2c_nuvoton_check_status(struct tpm_chip *chip, u8 mask, u8 value)
+{
+	u8 status = i2c_nuvoton_read_status(chip);
+	return (status != TPM_STS_ERR_VAL) && ((status & mask) == value);
+}
+
+static int i2c_nuvoton_wait_for_stat(struct tpm_chip *chip, u8 mask, u8 value,
+				     u32 timeout, wait_queue_head_t *queue)
+{
+	if (chip->vendor.irq && queue) {
+		s32 rc;
+		DEFINE_WAIT(wait);
+		struct priv_data *priv = chip->vendor.priv;
+		unsigned int cur_intrs = priv->intrs;
+
+		enable_irq(chip->vendor.irq);
+		rc = wait_event_interruptible_timeout(*queue,
+						      cur_intrs != priv->intrs,
+						      timeout);
+		if (rc > 0)
+			return 0;
+		/* At this point we know that the SINT pin is asserted, so we
+		 * do not need to do i2c_nuvoton_check_status */
+	} else {
+		unsigned long ten_msec, stop;
+		bool status_valid;
+
+		/* check current status */
+		status_valid = i2c_nuvoton_check_status(chip, mask, value);
+		if (status_valid)
+			return 0;
+
+		/* use polling to wait for the event */
+		ten_msec = jiffies + msecs_to_jiffies(TPM_I2C_RETRY_DELAY_LONG);
+		stop = jiffies + timeout;
+		do {
+			if (time_before(jiffies, ten_msec))
+				msleep(TPM_I2C_RETRY_DELAY_SHORT);
+			else
+				msleep(TPM_I2C_RETRY_DELAY_LONG);
+			status_valid = i2c_nuvoton_check_status(chip, mask,
+								value);
+			if (status_valid)
+				return 0;
+		} while (time_before(jiffies, stop));
+	}
+	dev_err(chip->dev, "%s(%02x, %02x) -> timeout\n", __func__, mask,
+		value);
+	return -ETIMEDOUT;
+}
+
+/* wait for dataAvail field to be set in the TPM_STS register */
+static int i2c_nuvoton_wait_for_data_avail(struct tpm_chip *chip, u32 timeout,
+					   wait_queue_head_t *queue)
+{
+	return i2c_nuvoton_wait_for_stat(chip,
+					 TPM_STS_DATA_AVAIL | TPM_STS_VALID,
+					 TPM_STS_DATA_AVAIL | TPM_STS_VALID,
+					 timeout, queue);
+}
+
+/* Read @count bytes into @buf from TPM_RD_FIFO register */
+static int i2c_nuvoton_recv_data(struct i2c_client *client,
+				 struct tpm_chip *chip, u8 *buf, size_t count)
+{
+	s32 rc;
+	int burst_count, bytes2read, size = 0;
+
+	while (size < count &&
+	       i2c_nuvoton_wait_for_data_avail(chip,
+					       chip->vendor.timeout_c,
+					       &chip->vendor.read_queue) == 0) {
+		burst_count = i2c_nuvoton_get_burstcount(client, chip);
+		if (burst_count < 0) {
+			dev_err(chip->dev,
+				"%s() fail to read burstCount=%d\n", __func__,
+				burst_count);
+			return -EIO;
+		}
+		bytes2read = min_t(size_t, burst_count, count - size);
+		rc = i2c_nuvoton_read_buf(client, TPM_DATA_FIFO_R,
+					  bytes2read, &buf[size]);
+		if (rc < 0) {
+			dev_err(chip->dev,
+				"%s() fail on i2c_nuvoton_read_buf()=%d\n",
+				__func__, rc);
+			return -EIO;
+		}
+		dev_dbg(chip->dev, "%s(%d):", __func__, bytes2read);
+		size += bytes2read;
+	}
+
+	return size;
+}
+
+/* Read TPM command results */
+static int i2c_nuvoton_recv(struct tpm_chip *chip, u8 *buf, size_t count)
+{
+	struct device *dev = chip->dev;
+	struct i2c_client *client = to_i2c_client(dev);
+	s32 rc;
+	int expected, status, burst_count, retries, size = 0;
+
+	if (count < TPM_HEADER_SIZE) {
+		i2c_nuvoton_ready(chip);    /* return to idle */
+		dev_err(dev, "%s() count < header size\n", __func__);
+		return -EIO;
+	}
+	for (retries = 0; retries < TPM_RETRY; retries++) {
+		if (retries > 0) {
+			/* if this is not the first trial, set responseRetry */
+			i2c_nuvoton_write_status(client,
+						 TPM_STS_RESPONSE_RETRY);
+		}
+		/*
+		 * read first available (> 10 bytes), including:
+		 * tag, paramsize, and result
+		 */
+		status = i2c_nuvoton_wait_for_data_avail(
+			chip, chip->vendor.timeout_c, &chip->vendor.read_queue);
+		if (status != 0) {
+			dev_err(dev, "%s() timeout on dataAvail\n", __func__);
+			size = -ETIMEDOUT;
+			continue;
+		}
+		burst_count = i2c_nuvoton_get_burstcount(client, chip);
+		if (burst_count < 0) {
+			dev_err(dev, "%s() fail to get burstCount\n", __func__);
+			size = -EIO;
+			continue;
+		}
+		size = i2c_nuvoton_recv_data(client, chip, buf,
+					     burst_count);
+		if (size < TPM_HEADER_SIZE) {
+			dev_err(dev, "%s() fail to read header\n", __func__);
+			size = -EIO;
+			continue;
+		}
+		/*
+		 * convert number of expected bytes field from big endian 32 bit
+		 * to machine native
+		 */
+		expected = be32_to_cpu(*(__be32 *) (buf + 2));
+		if (expected > count) {
+			dev_err(dev, "%s() expected > count\n", __func__);
+			size = -EIO;
+			continue;
+		}
+		rc = i2c_nuvoton_recv_data(client, chip, &buf[size],
+					   expected - size);
+		size += rc;
+		if (rc < 0 || size < expected) {
+			dev_err(dev, "%s() fail to read remainder of result\n",
+				__func__);
+			size = -EIO;
+			continue;
+		}
+		if (i2c_nuvoton_wait_for_stat(
+			    chip, TPM_STS_VALID | TPM_STS_DATA_AVAIL,
+			    TPM_STS_VALID, chip->vendor.timeout_c,
+			    NULL)) {
+			dev_err(dev, "%s() error left over data\n", __func__);
+			size = -ETIMEDOUT;
+			continue;
+		}
+		break;
+	}
+	i2c_nuvoton_ready(chip);
+	dev_dbg(chip->dev, "%s() -> %d\n", __func__, size);
+	return size;
+}
+
+/*
+ * Send TPM command.
+ *
+ * If interrupts are used (signaled by an irq set in the vendor structure)
+ * tpm.c can skip polling for the data to be available as the interrupt is
+ * waited for here
+ */
+static int i2c_nuvoton_send(struct tpm_chip *chip, u8 *buf, size_t len)
+{
+	struct device *dev = chip->dev;
+	struct i2c_client *client = to_i2c_client(dev);
+	u32 ordinal;
+	size_t count = 0;
+	int burst_count, bytes2write, retries, rc = -EIO;
+
+	for (retries = 0; retries < TPM_RETRY; retries++) {
+		i2c_nuvoton_ready(chip);
+		if (i2c_nuvoton_wait_for_stat(chip, TPM_STS_COMMAND_READY,
+					      TPM_STS_COMMAND_READY,
+					      chip->vendor.timeout_b, NULL)) {
+			dev_err(dev, "%s() timeout on commandReady\n",
+				__func__);
+			rc = -EIO;
+			continue;
+		}
+		rc = 0;
+		while (count < len - 1) {
+			burst_count = i2c_nuvoton_get_burstcount(client,
+								 chip);
+			if (burst_count < 0) {
+				dev_err(dev, "%s() fail get burstCount\n",
+					__func__);
+				rc = -EIO;
+				break;
+			}
+			bytes2write = min_t(size_t, burst_count,
+					    len - 1 - count);
+			rc = i2c_nuvoton_write_buf(client, TPM_DATA_FIFO_W,
+						   bytes2write, &buf[count]);
+			if (rc < 0) {
+				dev_err(dev, "%s() fail i2cWriteBuf\n",
+					__func__);
+				break;
+			}
+			dev_dbg(dev, "%s(%d):", __func__, bytes2write);
+			count += bytes2write;
+			rc = i2c_nuvoton_wait_for_stat(chip,
+						       TPM_STS_VALID |
+						       TPM_STS_EXPECT,
+						       TPM_STS_VALID |
+						       TPM_STS_EXPECT,
+						       chip->vendor.timeout_c,
+						       NULL);
+			if (rc < 0) {
+				dev_err(dev, "%s() timeout on Expect\n",
+					__func__);
+				rc = -ETIMEDOUT;
+				break;
+			}
+		}
+		if (rc < 0)
+			continue;
+
+		/* write last byte */
+		rc = i2c_nuvoton_write_buf(client, TPM_DATA_FIFO_W, 1,
+					   &buf[count]);
+		if (rc < 0) {
+			dev_err(dev, "%s() fail to write last byte\n",
+				__func__);
+			rc = -EIO;
+			continue;
+		}
+		dev_dbg(dev, "%s(last): %02x", __func__, buf[count]);
+		rc = i2c_nuvoton_wait_for_stat(chip,
+					       TPM_STS_VALID | TPM_STS_EXPECT,
+					       TPM_STS_VALID,
+					       chip->vendor.timeout_c, NULL);
+		if (rc) {
+			dev_err(dev, "%s() timeout on Expect to clear\n",
+				__func__);
+			rc = -ETIMEDOUT;
+			continue;
+		}
+		break;
+	}
+	if (rc < 0) {
+		/* retries == TPM_RETRY */
+		i2c_nuvoton_ready(chip);
+		return rc;
+	}
+	/* execute the TPM command */
+	rc = i2c_nuvoton_write_status(client, TPM_STS_GO);
+	if (rc < 0) {
+		dev_err(dev, "%s() fail to write Go\n", __func__);
+		i2c_nuvoton_ready(chip);
+		return rc;
+	}
+	ordinal = be32_to_cpu(*((__be32 *) (buf + 6)));
+	rc = i2c_nuvoton_wait_for_data_avail(chip,
+					     tpm_calc_ordinal_duration(chip,
+								       ordinal),
+					     &chip->vendor.read_queue);
+	if (rc) {
+		dev_err(dev, "%s() timeout command duration\n", __func__);
+		i2c_nuvoton_ready(chip);
+		return rc;
+	}
+
+	dev_dbg(dev, "%s() -> %zd\n", __func__, len);
+	return len;
+}
+
+static bool i2c_nuvoton_req_canceled(struct tpm_chip *chip, u8 status)
+{
+	return (status == TPM_STS_COMMAND_READY);
+}
+
+static const struct file_operations i2c_nuvoton_ops = {
+	.owner = THIS_MODULE,
+	.llseek = no_llseek,
+	.open = tpm_open,
+	.read = tpm_read,
+	.write = tpm_write,
+	.release = tpm_release,
+};
+
+static DEVICE_ATTR(pubek, S_IRUGO, tpm_show_pubek, NULL);
+static DEVICE_ATTR(pcrs, S_IRUGO, tpm_show_pcrs, NULL);
+static DEVICE_ATTR(enabled, S_IRUGO, tpm_show_enabled, NULL);
+static DEVICE_ATTR(active, S_IRUGO, tpm_show_active, NULL);
+static DEVICE_ATTR(owned, S_IRUGO, tpm_show_owned, NULL);
+static DEVICE_ATTR(temp_deactivated, S_IRUGO, tpm_show_temp_deactivated, NULL);
+static DEVICE_ATTR(caps, S_IRUGO, tpm_show_caps, NULL);
+static DEVICE_ATTR(cancel, S_IWUSR | S_IWGRP, NULL, tpm_store_cancel);
+static DEVICE_ATTR(durations, S_IRUGO, tpm_show_durations, NULL);
+static DEVICE_ATTR(timeouts, S_IRUGO, tpm_show_timeouts, NULL);
+
+static struct attribute *i2c_nuvoton_attrs[] = {
+	&dev_attr_pubek.attr,
+	&dev_attr_pcrs.attr,
+	&dev_attr_enabled.attr,
+	&dev_attr_active.attr,
+	&dev_attr_owned.attr,
+	&dev_attr_temp_deactivated.attr,
+	&dev_attr_caps.attr,
+	&dev_attr_cancel.attr,
+	&dev_attr_durations.attr,
+	&dev_attr_timeouts.attr,
+	NULL,
+};
+
+static struct attribute_group i2c_nuvoton_attr_grp = {
+	.attrs = i2c_nuvoton_attrs
+};
+
+static const struct tpm_vendor_specific tpm_i2c = {
+	.status = i2c_nuvoton_read_status,
+	.recv = i2c_nuvoton_recv,
+	.send = i2c_nuvoton_send,
+	.cancel = i2c_nuvoton_ready,
+	.req_complete_mask = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
+	.req_complete_val = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
+	.req_canceled = i2c_nuvoton_req_canceled,
+	.attr_group = &i2c_nuvoton_attr_grp,
+	.miscdev.fops = &i2c_nuvoton_ops,
+};
+
+/* The only purpose for the handler is to signal to any waiting threads that
+ * the interrupt is currently being asserted. The driver does not do any
+ * processing triggered by interrupts, and the chip provides no way to mask at
+ * the source (plus that would be slow over I2C). Run the IRQ as a one-shot,
+ * this means it cannot be shared. */
+static irqreturn_t i2c_nuvoton_int_handler(int dummy, void *dev_id)
+{
+	struct tpm_chip *chip = dev_id;
+	struct priv_data *priv = chip->vendor.priv;
+
+	priv->intrs++;
+	wake_up(&chip->vendor.read_queue);
+	disable_irq_nosync(chip->vendor.irq);
+	return IRQ_HANDLED;
+}
+
+static int get_vid(struct i2c_client *client, u32 *res)
+{
+	static const u8 vid_did_rid_value[] = { 0x50, 0x10, 0xfe };
+	u32 temp;
+	s32 rc;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -ENODEV;
+	rc = i2c_nuvoton_read_buf(client, TPM_VID_DID_RID, 4, (u8 *)&temp);
+	if (rc < 0)
+		return rc;
+
+	/* check WPCT301 values - ignore RID */
+	if (memcmp(&temp, vid_did_rid_value, sizeof(vid_did_rid_value))) {
+		/*
+		 * f/w rev 2.81 has an issue where the VID_DID_RID is not
+		 * reporting the right value. so give it another chance at
+		 * offset 0x20 (FIFO_W).
+		 */
+		rc = i2c_nuvoton_read_buf(client, TPM_DATA_FIFO_W, 4,
+					  (u8 *) (&temp));
+		if (rc < 0)
+			return rc;
+
+		/* check WPCT301 values - ignore RID */
+		if (memcmp(&temp, vid_did_rid_value,
+			   sizeof(vid_did_rid_value)))
+			return -ENODEV;
+	}
+
+	*res = temp;
+	return 0;
+}
+
+static int i2c_nuvoton_probe(struct i2c_client *client,
+			     const struct i2c_device_id *id)
+{
+	int rc;
+	struct tpm_chip *chip;
+	struct device *dev = &client->dev;
+	u32 vid = 0;
+
+	rc = get_vid(client, &vid);
+	if (rc)
+		return rc;
+
+	dev_info(dev, "VID: %04X DID: %02X RID: %02X\n", (u16) vid,
+		 (u8) (vid >> 16), (u8) (vid >> 24));
+
+	chip = tpm_register_hardware(dev, &tpm_i2c);
+	if (!chip) {
+		dev_err(dev, "%s() error in tpm_register_hardware\n", __func__);
+		return -ENODEV;
+	}
+
+	chip->vendor.priv = devm_kzalloc(dev, sizeof(struct priv_data),
+					 GFP_KERNEL);
+	init_waitqueue_head(&chip->vendor.read_queue);
+	init_waitqueue_head(&chip->vendor.int_queue);
+
+	/* Default timeouts */
+	chip->vendor.timeout_a = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
+	chip->vendor.timeout_b = msecs_to_jiffies(TPM_I2C_LONG_TIMEOUT);
+	chip->vendor.timeout_c = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
+	chip->vendor.timeout_d = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
+
+	/*
+	 * I2C intfcaps (interrupt capabilitieis) in the chip are hard coded to:
+	 *   TPM_INTF_INT_LEVEL_LOW | TPM_INTF_DATA_AVAIL_INT
+	 * The IRQ should be set in the i2c_board_info (which is done
+	 * automatically in of_i2c_register_devices, for device tree users */
+	chip->vendor.irq = client->irq;
+
+	if (chip->vendor.irq) {
+		dev_dbg(dev, "%s() chip-vendor.irq\n", __func__);
+		rc = devm_request_irq(dev, chip->vendor.irq,
+				      i2c_nuvoton_int_handler,
+				      IRQF_TRIGGER_LOW,
+				      chip->vendor.miscdev.name,
+				      chip);
+		if (rc) {
+			dev_err(dev, "%s() Unable to request irq: %d for use\n",
+				__func__, chip->vendor.irq);
+			chip->vendor.irq = 0;
+		} else {
+			/* Clear any pending interrupt */
+			i2c_nuvoton_ready(chip);
+			/* - wait for TPM_STS==0xA0 (stsValid, commandReady) */
+			rc = i2c_nuvoton_wait_for_stat(chip,
+						       TPM_STS_COMMAND_READY,
+						       TPM_STS_COMMAND_READY,
+						       chip->vendor.timeout_b,
+						       NULL);
+			if (rc == 0) {
+				/*
+				 * TIS is in ready state
+				 * write dummy byte to enter reception state
+				 * TPM_DATA_FIFO_W <- rc (0)
+				 */
+				rc = i2c_nuvoton_write_buf(client,
+							   TPM_DATA_FIFO_W,
+							   1, (u8 *) (&rc));
+				if (rc < 0)
+					goto out_err;
+				/* TPM_STS <- 0x40 (commandReady) */
+				i2c_nuvoton_ready(chip);
+			} else {
+				/*
+				 * timeout_b reached - command was
+				 * aborted. TIS should now be in idle state -
+				 * only TPM_STS_VALID should be set
+				 */
+				if (i2c_nuvoton_read_status(chip) !=
+				    TPM_STS_VALID) {
+					rc = -EIO;
+					goto out_err;
+				}
+			}
+		}
+	}
+
+	if (tpm_get_timeouts(chip)) {
+		rc = -ENODEV;
+		goto out_err;
+	}
+
+	if (tpm_do_selftest(chip)) {
+		rc = -ENODEV;
+		goto out_err;
+	}
+
+	return 0;
+
+out_err:
+	tpm_dev_vendor_release(chip);
+	tpm_remove_hardware(chip->dev);
+	return rc;
+}
+
+static int i2c_nuvoton_remove(struct i2c_client *client)
+{
+	struct device *dev = &(client->dev);
+	struct tpm_chip *chip = dev_get_drvdata(dev);
+
+	if (chip)
+		tpm_dev_vendor_release(chip);
+	tpm_remove_hardware(dev);
+	kfree(chip);
+	return 0;
+}
+
+
+static const struct i2c_device_id i2c_nuvoton_id[] = {
+	{I2C_DRIVER_NAME, 0},
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, i2c_nuvoton_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id i2c_nuvoton_of_match[] = {
+	{.compatible = "nuvoton,npct501"},
+	{.compatible = "winbond,wpct301"},
+	{},
+};
+MODULE_DEVICE_TABLE(of, i2c_nuvoton_of_match);
+#endif
+
+static SIMPLE_DEV_PM_OPS(i2c_nuvoton_pm_ops, tpm_pm_suspend, tpm_pm_resume);
+
+static struct i2c_driver i2c_nuvoton_driver = {
+	.id_table = i2c_nuvoton_id,
+	.probe = i2c_nuvoton_probe,
+	.remove = i2c_nuvoton_remove,
+	.driver = {
+		.name = I2C_DRIVER_NAME,
+		.owner = THIS_MODULE,
+		.pm = &i2c_nuvoton_pm_ops,
+		.of_match_table = of_match_ptr(i2c_nuvoton_of_match),
+	},
+};
+
+module_i2c_driver(i2c_nuvoton_driver);
+
+MODULE_AUTHOR("Dan Morav (dan.morav@nuvoton.com)");
+MODULE_DESCRIPTION("Nuvoton TPM I2C Driver");
+MODULE_LICENSE("GPL");