tpm: Add support for Atmel I2C TPMs

This is based on the work of Teddy Reed <teddy@prosauce.org> published
on GitHub:
 https://github.com/theopolis/tpm-i2c-atmel.git
 34894b988b67e0ae55088d6388e77b0dbf10c07d

That driver was never merged, I have taken it as a starting port,
forward ported, tested and revised the driver:
 - Make it broadly textually similar to the Infineon and Nuvoton I2C
   driver
 - Place everything in a format suitable for mainline inclusion
 - Use high level I2C functions i2c_master_send and
   i2c_master_recv for data xfer
 - Use the timeout system from the core code, by faking out a status
   register
 - Only I2C transfer the number of bytes in the reply, not a fixed
   message size.
 - checkpatch cleanups
 - Testing on ARM Kirkwood, with this device tree, using a
   AT97SC3204T-X1A180
        tpm@29 {
                compatible = "atmel,at97sc3204t";
                reg = <0x29>;
        };

Signed-off-by: Teddy Reed <teddy@prosauce.org>
[jgg: revised and tested]
Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
[phuewe: minor whitespace changes]

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

4 files changed, 295 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/i2c/trivial-devices.txt b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
index 58454bdfa20e..f1fb26eed0e9 100644
--- a/Documentation/devicetree/bindings/i2c/trivial-devices.txt
+++ b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
@@ -15,6 +15,7 @@ adi,adt7461		+/-1C TDM Extended Temp Range I.C
 adt7461                 +/-1C TDM Extended Temp Range I.C
 at,24c08                i2c serial eeprom  (24cxx)
 atmel,24c02             i2c serial eeprom  (24cxx)
+atmel,at97sc3204t       i2c trusted platform module (TPM)
 catalyst,24c32          i2c serial eeprom
 dallas,ds1307           64 x 8, Serial, I2C Real-Time Clock
 dallas,ds1338           I2C RTC with 56-Byte NV RAM
diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index ade71c134a1a..f9085860b716 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -33,6 +33,15 @@ config TCG_TIS
           from within Linux.  To compile this driver as a module, choose
           M here; the module will be called tpm_tis.
 
+config TCG_TIS_I2C_ATMEL
+        tristate "TPM Interface Specification 1.2 Interface (I2C - Atmel)"
+        depends on I2C
+        ---help---
+          If you have an Atmel I2C TPM security chip 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_tis_i2c_atmel.
+
 config TCG_TIS_I2C_INFINEON
         tristate "TPM Interface Specification 1.2 Interface (I2C - Infineon)"
         depends on I2C
diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index 07ee67cf3341..b80a4000daee 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -13,6 +13,7 @@ ifdef CONFIG_TCG_IBMVTPM
 endif
 endif
 obj-$(CONFIG_TCG_TIS) += tpm_tis.o
+obj-$(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
 obj-$(CONFIG_TCG_NSC) += tpm_nsc.o
diff --git a/drivers/char/tpm/tpm_i2c_atmel.c b/drivers/char/tpm/tpm_i2c_atmel.c
new file mode 100644
index 000000000000..c3cd7fe481a1
--- /dev/null
+++ b/drivers/char/tpm/tpm_i2c_atmel.c
@@ -0,0 +1,284 @@
+/*
+ * ATMEL I2C TPM AT97SC3204T
+ *
+ * Copyright (C) 2012 V Lab Technologies
+ *  Teddy Reed <teddy@prosauce.org>
+ * Copyright (C) 2013, Obsidian Research Corp.
+ *  Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
+ * Device driver for ATMEL I2C TPMs.
+ *
+ * Teddy Reed determined the basic I2C command flow, unlike other I2C TPM
+ * devices the raw TCG formatted TPM command data is written via I2C and then
+ * raw TCG formatted TPM command data is returned via I2C.
+ *
+ * TGC status/locality/etc functions seen in the LPC implementation do not
+ * seem to be present.
+ *
+ * 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/>.
+ */
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include "tpm.h"
+
+#define I2C_DRIVER_NAME "tpm_i2c_atmel"
+
+#define TPM_I2C_SHORT_TIMEOUT  750     /* ms */
+#define TPM_I2C_LONG_TIMEOUT   2000    /* 2 sec */
+
+#define ATMEL_STS_OK 1
+
+struct priv_data {
+        size_t len;
+        /* This is the amount we read on the first try. 25 was chosen to fit a
+         * fair number of read responses in the buffer so a 2nd retry can be
+         * avoided in small message cases. */
+        u8 buffer[sizeof(struct tpm_output_header) + 25];
+};
+
+static int i2c_atmel_send(struct tpm_chip *chip, u8 *buf, size_t len)
+{
+        struct priv_data *priv = chip->vendor.priv;
+        struct i2c_client *client = to_i2c_client(chip->dev);
+        s32 status;
+
+        priv->len = 0;
+
+        if (len <= 2)
+                return -EIO;
+
+        status = i2c_master_send(client, buf, len);
+
+        dev_dbg(chip->dev,
+                "%s(buf=%*ph len=%0zx) -> sts=%d\n", __func__,
+                (int)min_t(size_t, 64, len), buf, len, status);
+        return status;
+}
+
+static int i2c_atmel_recv(struct tpm_chip *chip, u8 *buf, size_t count)
+{
+        struct priv_data *priv = chip->vendor.priv;
+        struct i2c_client *client = to_i2c_client(chip->dev);
+        struct tpm_output_header *hdr =
+                (struct tpm_output_header *)priv->buffer;
+        u32 expected_len;
+        int rc;
+
+        if (priv->len == 0)
+                return -EIO;
+
+        /* Get the message size from the message header, if we didn't get the
+         * whole message in read_status then we need to re-read the
+         * message. */
+        expected_len = be32_to_cpu(hdr->length);
+        if (expected_len > count)
+                return -ENOMEM;
+
+        if (priv->len >= expected_len) {
+                dev_dbg(chip->dev,
+                        "%s early(buf=%*ph count=%0zx) -> ret=%d\n", __func__,
+                        (int)min_t(size_t, 64, expected_len), buf, count,
+                        expected_len);
+                memcpy(buf, priv->buffer, expected_len);
+                return expected_len;
+        }
+
+        rc = i2c_master_recv(client, buf, expected_len);
+        dev_dbg(chip->dev,
+                "%s reread(buf=%*ph count=%0zx) -> ret=%d\n", __func__,
+                (int)min_t(size_t, 64, expected_len), buf, count,
+                expected_len);
+        return rc;
+}
+
+static void i2c_atmel_cancel(struct tpm_chip *chip)
+{
+        dev_err(chip->dev, "TPM operation cancellation was requested, but is not supported");
+}
+
+static u8 i2c_atmel_read_status(struct tpm_chip *chip)
+{
+        struct priv_data *priv = chip->vendor.priv;
+        struct i2c_client *client = to_i2c_client(chip->dev);
+        int rc;
+
+        /* The TPM fails the I2C read until it is ready, so we do the entire
+         * transfer here and buffer it locally. This way the common code can
+         * properly handle the timeouts. */
+        priv->len = 0;
+        memset(priv->buffer, 0, sizeof(priv->buffer));
+
+
+        /* Once the TPM has completed the command the command remains readable
+         * until another command is issued. */
+        rc = i2c_master_recv(client, priv->buffer, sizeof(priv->buffer));
+        dev_dbg(chip->dev,
+                "%s: sts=%d", __func__, rc);
+        if (rc <= 0)
+                return 0;
+
+        priv->len = rc;
+
+        return ATMEL_STS_OK;
+}
+
+static const struct file_operations i2c_atmel_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_atmel_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_atmel_attr_grp = {
+        .attrs = i2c_atmel_attrs
+};
+
+static bool i2c_atmel_req_canceled(struct tpm_chip *chip, u8 status)
+{
+        return 0;
+}
+
+static const struct tpm_vendor_specific i2c_atmel = {
+        .status = i2c_atmel_read_status,
+        .recv = i2c_atmel_recv,
+        .send = i2c_atmel_send,
+        .cancel = i2c_atmel_cancel,
+        .req_complete_mask = ATMEL_STS_OK,
+        .req_complete_val = ATMEL_STS_OK,
+        .req_canceled = i2c_atmel_req_canceled,
+        .attr_group = &i2c_atmel_attr_grp,
+        .miscdev.fops = &i2c_atmel_ops,
+};
+
+static int i2c_atmel_probe(struct i2c_client *client,
+                           const struct i2c_device_id *id)
+{
+        int rc;
+        struct tpm_chip *chip;
+        struct device *dev = &client->dev;
+
+        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+                return -ENODEV;
+
+        chip = tpm_register_hardware(dev, &i2c_atmel);
+        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);
+
+        /* 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);
+        chip->vendor.irq = 0;
+
+        /* There is no known way to probe for this device, and all version
+         * information seems to be read via TPM commands. Thus we rely on the
+         * TPM startup process in the common code to detect the device. */
+        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_atmel_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_atmel_id[] = {
+        {I2C_DRIVER_NAME, 0},
+        {}
+};
+MODULE_DEVICE_TABLE(i2c, i2c_atmel_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id i2c_atmel_of_match[] = {
+        {.compatible = "atmel,at97sc3204t"},
+        {},
+};
+MODULE_DEVICE_TABLE(of, i2c_atmel_of_match);
+#endif
+
+static SIMPLE_DEV_PM_OPS(i2c_atmel_pm_ops, tpm_pm_suspend, tpm_pm_resume);
+
+static struct i2c_driver i2c_atmel_driver = {
+        .id_table = i2c_atmel_id,
+        .probe = i2c_atmel_probe,
+        .remove = i2c_atmel_remove,
+        .driver = {
+                .name = I2C_DRIVER_NAME,
+                .owner = THIS_MODULE,
+                .pm = &i2c_atmel_pm_ops,
+                .of_match_table = of_match_ptr(i2c_atmel_of_match),
+        },
+};
+
+module_i2c_driver(i2c_atmel_driver);
+
+MODULE_AUTHOR("Jason Gunthorpe <jgunthorpe@obsidianresearch.com>");
+MODULE_DESCRIPTION("Atmel TPM I2C Driver");
+MODULE_LICENSE("GPL");