tpm: Add support for the Nuvoton NPCT501 I2C TPM
authorJason Gunthorpe <jgunthorpe@obsidianresearch.com>
Sun, 6 Oct 2013 18:43:13 +0000 (12:43 -0600)
committerPeter Huewe <peterhuewe@gmx.de>
Tue, 22 Oct 2013 17:43:04 +0000 (19:43 +0200)
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>
Documentation/devicetree/bindings/i2c/trivial-devices.txt
drivers/char/tpm/Kconfig
drivers/char/tpm/Makefile
drivers/char/tpm/tpm_i2c_nuvoton.c [new file with mode: 0644]

index ad6a738..58454bd 100644 (file)
@@ -44,6 +44,7 @@ mc,rv3029c2           Real Time Clock Module with I2C-Bus
 national,lm75          I2C TEMP SENSOR
 national,lm80          Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor
 national,lm92          ±0.33°C Accurate, 12-Bit + Sign Temperature Sensor and Thermal Window Comparator with Two-Wire Interface
+nuvoton,npct501                i2c trusted platform module (TPM)
 nxp,pca9556            Octal SMBus and I2C registered interface
 nxp,pca9557            8-bit I2C-bus and SMBus I/O port with reset
 nxp,pcf8563            Real-time clock/calendar
@@ -61,3 +62,4 @@ taos,tsl2550          Ambient Light Sensor with SMBUS/Two Wire Serial Interface
 ti,tsc2003             I2C Touch-Screen Controller
 ti,tmp102              Low Power Digital Temperature Sensor with SMBUS/Two Wire Serial Interface
 ti,tmp275              Digital Temperature Sensor
+winbond,wpct301                i2c trusted platform module (TPM)
index 94c0c74..ade71c1 100644 (file)
@@ -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
index 15df2f3..07ee67c 100644 (file)
@@ -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 (file)
index 0000000..6276fea
--- /dev/null
@@ -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");