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>

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

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

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

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");