Introduce generic TPM support in u-boot

TPM (Trusted Platform Module) is an integrated circuit and
software platform that provides computer manufacturers with the
core components of a subsystem used to assure authenticity,
integrity and confidentiality.

This driver supports version 1.2 of the TCG (Trusted Computing
Group) specifications.

The TCG specification defines several so called localities in a
TPM chip, to be controlled by different software layers. When
used on a typical x86 platform during the firmware phase, only
locality 0 can be accessed by the CPU, so this driver even while
supporting the locality concept presumes that only locality zero
is used.

This implementation is loosely based on the article "Writing a
TPM Device Driver" published on http://ptgmedia.pearsoncmg.com

Compiling this driver with DEBUG defined will generate trace of
all accesses to TMP registers.

This driver has been tested and is being used in three different
functional ChromeOS machines (Pinetrail and Sandy Bridge Intel
chipsets) all using the same Infineon SLB 9635 TT 1.2 device.

A u-boot cli command allowing access to the TPM was also
implemented and is being submitted as a second patch.

Change-Id: I22a33c3e5b2e20eec9557a7621bd463b30389d73
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
CC: Wolfgang Denk <wd@denx.de>

2 files changed, 538 insertions, 0 deletions

diff --git a/drivers/tpm/Makefile b/drivers/tpm/Makefile
new file mode 100644
index 0000000..be11c8b
--- /dev/null
+++ b/drivers/tpm/Makefile
@@ -0,0 +1,43 @@
+# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
+#
+# See file CREDITS for list of people who contributed to this
+# project.
+#
+# 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, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+# MA 02111-1307 USA
+#
+
+include $(TOPDIR)/config.mk
+
+LIB := $(obj)libtpm.o
+
+COBJS-$(CONFIG_GENERIC_LPC_TPM) = generic_lpc_tpm.o
+
+COBJS	:= $(COBJS-y)
+SRCS	:= $(COBJS:.o=.c)
+OBJS	:= $(addprefix $(obj),$(COBJS))
+
+all:	$(LIB)
+
+$(LIB): $(obj).depend $(OBJS)
+	$(call cmd_link_o_target, $(OBJS))
+
+#########################################################################
+
+include $(SRCTREE)/rules.mk
+
+sinclude $(obj).depend
+
+#########################################################################
diff --git a/drivers/tpm/generic_lpc_tpm.c b/drivers/tpm/generic_lpc_tpm.c
new file mode 100644
index 0000000..6c494eb
--- /dev/null
+++ b/drivers/tpm/generic_lpc_tpm.c
@@ -0,0 +1,495 @@
+/*
+ * Copyright (c) 2011 The Chromium OS Authors.
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+/*
+ * The code in this file is based on the article "Writing a TPM Device Driver"
+ * published on http://ptgmedia.pearsoncmg.com.
+ *
+ * One principal difference is that in the simplest config the other than 0
+ * TPM localities do not get mapped by some devices (for instance, by Infineon
+ * slb9635), so this driver provides access to locality 0 only.
+ */
+
+#include <common.h>
+#include <asm/io.h>
+#include <tpm.h>
+
+#define PREFIX "lpc_tpm: "
+
+struct tpm_locality {
+	u32 access;
+	u8 padding0[4];
+	u32 int_enable;
+	u8 vector;
+	u8 padding1[3];
+	u32 int_status;
+	u32 int_capability;
+	u32 tpm_status;
+	u8 padding2[8];
+	u8 data;
+	u8 padding3[3803];
+	u32 did_vid;
+	u8 rid;
+	u8 padding4[251];
+};
+
+/*
+ * This pointer refers to the TPM chip, 5 of its localities are mapped as an
+ * array.
+ */
+#define TPM_TOTAL_LOCALITIES	5
+static struct tpm_locality *lpc_tpm_dev =
+	(struct tpm_locality *)CONFIG_TPM_TIS_BASE_ADDRESS;
+
+/* Some registers' bit field definitions */
+#define TIS_STS_VALID                  (1 << 7) /* 0x80 */
+#define TIS_STS_COMMAND_READY          (1 << 6) /* 0x40 */
+#define TIS_STS_TPM_GO                 (1 << 5) /* 0x20 */
+#define TIS_STS_DATA_AVAILABLE         (1 << 4) /* 0x10 */
+#define TIS_STS_EXPECT                 (1 << 3) /* 0x08 */
+#define TIS_STS_RESPONSE_RETRY         (1 << 1) /* 0x02 */
+
+#define TIS_ACCESS_TPM_REG_VALID_STS   (1 << 7) /* 0x80 */
+#define TIS_ACCESS_ACTIVE_LOCALITY     (1 << 5) /* 0x20 */
+#define TIS_ACCESS_BEEN_SEIZED         (1 << 4) /* 0x10 */
+#define TIS_ACCESS_SEIZE               (1 << 3) /* 0x08 */
+#define TIS_ACCESS_PENDING_REQUEST     (1 << 2) /* 0x04 */
+#define TIS_ACCESS_REQUEST_USE         (1 << 1) /* 0x02 */
+#define TIS_ACCESS_TPM_ESTABLISHMENT   (1 << 0) /* 0x01 */
+
+#define TIS_STS_BURST_COUNT_MASK       (0xffff)
+#define TIS_STS_BURST_COUNT_SHIFT      (8)
+
+/*
+ * Error value returned if a tpm register does not enter the expected state
+ * after continuous polling. No actual TPM register reading ever returns -1,
+ * so this value is a safe error indication to be mixed with possible status
+ * register values.
+ */
+#define TPM_TIMEOUT_ERR			(-1)
+
+/* Error value returned on various TPM driver errors. */
+#define TPM_DRIVER_ERR		(1)
+
+ /* 1 second is plenty for anything TPM does. */
+#define MAX_DELAY_US	(1000 * 1000)
+
+/* Retrieve burst count value out of the status register contents. */
+static u16 burst_count(u32 status)
+{
+	return (status >> TIS_STS_BURST_COUNT_SHIFT) & TIS_STS_BURST_COUNT_MASK;
+}
+
+/*
+ * Structures defined below allow creating descriptions of TPM vendor/device
+ * ID information for run time discovery. The only device the system knows
+ * about at this time is Infineon slb9635.
+ */
+struct device_name {
+	u16 dev_id;
+	const char * const dev_name;
+};
+
+struct vendor_name {
+	u16 vendor_id;
+	const char *vendor_name;
+	const struct device_name *dev_names;
+};
+
+static const struct device_name infineon_devices[] = {
+	{0xb, "SLB9635 TT 1.2"},
+	{0}
+};
+
+static const struct vendor_name vendor_names[] = {
+	{0x15d1, "Infineon", infineon_devices},
+};
+
+/*
+ * Cached vendor/device ID pair to indicate that the device has been already
+ * discovered.
+ */
+static u32 vendor_dev_id;
+
+/* TPM access wrappers to support tracing */
+static u8 tpm_read_byte(const u8 *ptr)
+{
+	u8  ret = readb(ptr);
+	debug(PREFIX "Read reg 0x%4.4x returns 0x%2.2x\n",
+	      (u32)ptr - (u32)lpc_tpm_dev, ret);
+	return ret;
+}
+
+static u32 tpm_read_word(const u32 *ptr)
+{
+	u32  ret = readl(ptr);
+	debug(PREFIX "Read reg 0x%4.4x returns 0x%8.8x\n",
+	      (u32)ptr - (u32)lpc_tpm_dev, ret);
+	return ret;
+}
+
+static void tpm_write_byte(u8 value, u8 *ptr)
+{
+	debug(PREFIX "Write reg 0x%4.4x with 0x%2.2x\n",
+	      (u32)ptr - (u32)lpc_tpm_dev, value);
+	writeb(value, ptr);
+}
+
+static void tpm_write_word(u32 value, u32 *ptr)
+{
+	debug(PREFIX "Write reg 0x%4.4x with 0x%8.8x\n",
+	      (u32)ptr - (u32)lpc_tpm_dev, value);
+	writel(value, ptr);
+}
+
+/*
+ * tis_wait_reg()
+ *
+ * Wait for at least a second for a register to change its state to match the
+ * expected state. Normally the transition happens within microseconds.
+ *
+ * @reg - pointer to the TPM register
+ * @mask - bitmask for the bitfield(s) to watch
+ * @expected - value the field(s) are supposed to be set to
+ *
+ * Returns the register contents in case the expected value was found in the
+ * appropriate register bits, or TPM_TIMEOUT_ERR on timeout.
+ */
+static u32 tis_wait_reg(u32 *reg, u8 mask, u8 expected)
+{
+	u32 time_us = MAX_DELAY_US;
+
+	while (time_us > 0) {
+		u32 value = tpm_read_word(reg);
+		if ((value & mask) == expected)
+			return value;
+		udelay(1); /* 1 us */
+		time_us--;
+	}
+	return TPM_TIMEOUT_ERR;
+}
+
+/*
+ * Probe the TPM device and try determining its manufacturer/device name.
+ *
+ * Returns 0 on success (the device is found or was found during an earlier
+ * invocation) or TPM_DRIVER_ERR if the device is not found.
+ */
+int tis_init(void)
+{
+	u32 didvid = tpm_read_word(&lpc_tpm_dev[0].did_vid);
+	int i;
+	const char *device_name = "unknown";
+	const char *vendor_name = device_name;
+	u16 vid, did;
+
+	if (vendor_dev_id)
+		return 0;  /* Already probed. */
+
+	if (!didvid || (didvid == 0xffffffff)) {
+		printf("%s: No TPM device found\n", __func__);
+		return TPM_DRIVER_ERR;
+	}
+
+	vendor_dev_id = didvid;
+
+	vid = didvid & 0xffff;
+	did = (didvid >> 16) & 0xffff;
+	for (i = 0; i < ARRAY_SIZE(vendor_names); i++) {
+		int j = 0;
+		u16 known_did;
+
+		if (vid == vendor_names[i].vendor_id)
+			vendor_name = vendor_names[i].vendor_name;
+
+		while ((known_did = vendor_names[i].dev_names[j].dev_id) != 0) {
+			if (known_did == did) {
+				device_name =
+					vendor_names[i].dev_names[j].dev_name;
+				break;
+			}
+			j++;
+		}
+		break;
+	}
+
+	printf("Found TPM %s by %s\n", device_name, vendor_name);
+	return 0;
+}
+
+/*
+ * tis_senddata()
+ *
+ * send the passed in data to the TPM device.
+ *
+ * @data - address of the data to send, byte by byte
+ * @len - length of the data to send
+ *
+ * Returns 0 on success, TPM_DRIVER_ERR on error (in case the device does
+ * not accept the entire command).
+ */
+static u32 tis_senddata(const u8 * const data, u32 len)
+{
+	u32 offset = 0;
+	u16 burst = 0;
+	u32 max_cycles = 0;
+	u8 locality = 0;
+	u32 value;
+
+	value = tis_wait_reg(&lpc_tpm_dev[locality].tpm_status,
+			     TIS_STS_COMMAND_READY, TIS_STS_COMMAND_READY);
+	if (value == TPM_TIMEOUT_ERR) {
+		printf("%s:%d - failed to get 'command_ready' status\n",
+		       __FILE__, __LINE__);
+		return TPM_DRIVER_ERR;
+	}
+	burst = burst_count(value);
+
+	while (1) {
+		unsigned count;
+
+		/* Wait till the device is ready to accept more data. */
+		while (!burst) {
+			if (max_cycles++ == MAX_DELAY_US) {
+				printf("%s:%d failed to feed %d bytes of %d\n",
+				       __FILE__, __LINE__, len - offset, len);
+				return TPM_DRIVER_ERR;
+			}
+			udelay(1);
+			burst = burst_count(tpm_read_word(&lpc_tpm_dev
+						     [locality].tpm_status));
+		}
+
+		max_cycles = 0;
+
+		/*
+		 * Calculate number of bytes the TPM is ready to accept in one
+		 * shot.
+		 *
+		 * We want to send the last byte outside of the loop (hence
+		 * the -1 below) to make sure that the 'expected' status bit
+		 * changes to zero exactly after the last byte is fed into the
+		 * FIFO.
+		 */
+		count = min(burst, len - offset - 1);
+		while (count--)
+			tpm_write_byte(data[offset++],
+				  &lpc_tpm_dev[locality].data);
+
+		value = tis_wait_reg(&lpc_tpm_dev[locality].tpm_status,
+				     TIS_STS_VALID, TIS_STS_VALID);
+
+		if ((value == TPM_TIMEOUT_ERR) || !(value & TIS_STS_EXPECT)) {
+			printf("%s:%d TPM command feed overflow\n",
+			       __FILE__, __LINE__);
+			return TPM_DRIVER_ERR;
+		}
+
+		burst = burst_count(value);
+		if ((offset == (len - 1)) && burst) {
+			/*
+			 * We need to be able to send the last byte to the
+			 * device, so burst size must be nonzero before we
+			 * break out.
+			 */
+			break;
+		}
+	}
+
+	/* Send the last byte. */
+	tpm_write_byte(data[offset++], &lpc_tpm_dev[locality].data);
+	/*
+	 * Verify that TPM does not expect any more data as part of this
+	 * command.
+	 */
+	value = tis_wait_reg(&lpc_tpm_dev[locality].tpm_status,
+			     TIS_STS_VALID, TIS_STS_VALID);
+	if ((value == TPM_TIMEOUT_ERR) || (value & TIS_STS_EXPECT)) {
+		printf("%s:%d unexpected TPM status 0x%x\n",
+		       __FILE__, __LINE__, value);
+		return TPM_DRIVER_ERR;
+	}
+
+	/* OK, sitting pretty, let's start the command execution. */
+	tpm_write_word(TIS_STS_TPM_GO, &lpc_tpm_dev[locality].tpm_status);
+	return 0;
+}
+
+/*
+ * tis_readresponse()
+ *
+ * read the TPM device response after a command was issued.
+ *
+ * @buffer - address where to read the response, byte by byte.
+ * @len - pointer to the size of buffer
+ *
+ * On success stores the number of received bytes to len and returns 0. On
+ * errors (misformatted TPM data or synchronization problems) returns
+ * TPM_DRIVER_ERR.
+ */
+static u32 tis_readresponse(u8 *buffer, u32 *len)
+{
+	u16 burst;
+	u32 value;
+	u32 offset = 0;
+	u8 locality = 0;
+	const u32 has_data = TIS_STS_DATA_AVAILABLE | TIS_STS_VALID;
+	u32 expected_count = *len;
+	int max_cycles = 0;
+
+	/* Wait for the TPM to process the command. */
+	value = tis_wait_reg(&lpc_tpm_dev[locality].tpm_status,
+			      has_data, has_data);
+	if (value == TPM_TIMEOUT_ERR) {
+		printf("%s:%d failed processing command\n",
+		       __FILE__, __LINE__);
+		return TPM_DRIVER_ERR;
+	}
+
+	do {
+		while ((burst = burst_count(value)) == 0) {
+			if (max_cycles++ == MAX_DELAY_US) {
+				printf("%s:%d TPM stuck on read\n",
+				       __FILE__, __LINE__);
+				return TPM_DRIVER_ERR;
+			}
+			udelay(1);
+			value = tpm_read_word(&lpc_tpm_dev
+					      [locality].tpm_status);
+		}
+
+		max_cycles = 0;
+
+		while (burst-- && (offset < expected_count)) {
+			buffer[offset++] = tpm_read_byte(&lpc_tpm_dev
+							 [locality].data);
+
+			if (offset == 6) {
+				/*
+				 * We got the first six bytes of the reply,
+				 * let's figure out how many bytes to expect
+				 * total - it is stored as a 4 byte number in
+				 * network order, starting with offset 2 into
+				 * the body of the reply.
+				 */
+				u32 real_length;
+				memcpy(&real_length,
+				       buffer + 2,
+				       sizeof(real_length));
+				expected_count = be32_to_cpu(real_length);
+
+				if ((expected_count < offset) ||
+				    (expected_count > *len)) {
+					printf("%s:%d bad response size %d\n",
+					       __FILE__, __LINE__,
+					       expected_count);
+					return TPM_DRIVER_ERR;
+				}
+			}
+		}
+
+		/* Wait for the next portion. */
+		value = tis_wait_reg(&lpc_tpm_dev[locality].tpm_status,
+				     TIS_STS_VALID, TIS_STS_VALID);
+		if (value == TPM_TIMEOUT_ERR) {
+			printf("%s:%d failed to read response\n",
+			       __FILE__, __LINE__);
+			return TPM_DRIVER_ERR;
+		}
+
+		if (offset == expected_count)
+			break;	/* We got all we needed. */
+
+	} while ((value & has_data) == has_data);
+
+	/*
+	 * Make sure we indeed read all there was. The TIS_STS_VALID bit is
+	 * known to be set.
+	 */
+	if (value & TIS_STS_DATA_AVAILABLE) {
+		printf("%s:%d wrong receive status %x\n",
+		       __FILE__, __LINE__, value);
+		return TPM_DRIVER_ERR;
+	}
+
+	/* Tell the TPM that we are done. */
+	tpm_write_word(TIS_STS_COMMAND_READY, &lpc_tpm_dev
+		  [locality].tpm_status);
+	*len = offset;
+	return 0;
+}
+
+int tis_open(void)
+{
+	u8 locality = 0; /* we use locality zero for everything. */
+
+	if (tis_close())
+		return TPM_DRIVER_ERR;
+
+	/* now request access to locality. */
+	tpm_write_word(TIS_ACCESS_REQUEST_USE, &lpc_tpm_dev[locality].access);
+
+	/* did we get a lock? */
+	if (tis_wait_reg(&lpc_tpm_dev[locality].access,
+			 TIS_ACCESS_ACTIVE_LOCALITY,
+			 TIS_ACCESS_ACTIVE_LOCALITY) == TPM_TIMEOUT_ERR) {
+		printf("%s:%d - failed to lock locality %d\n",
+		       __FILE__, __LINE__, locality);
+		return TPM_DRIVER_ERR;
+	}
+
+	tpm_write_word(TIS_STS_COMMAND_READY,
+		       &lpc_tpm_dev[locality].tpm_status);
+	return 0;
+}
+
+int tis_close(void)
+{
+	u8 locality = 0;
+
+	if (tpm_read_word(&lpc_tpm_dev[locality].access) &
+	    TIS_ACCESS_ACTIVE_LOCALITY) {
+		tpm_write_word(TIS_ACCESS_ACTIVE_LOCALITY,
+			       &lpc_tpm_dev[locality].access);
+
+		if (tis_wait_reg(&lpc_tpm_dev[locality].access,
+				 TIS_ACCESS_ACTIVE_LOCALITY, 0) ==
+		    TPM_TIMEOUT_ERR) {
+			printf("%s:%d - failed to release locality %d\n",
+			       __FILE__, __LINE__, locality);
+			return TPM_DRIVER_ERR;
+		}
+	}
+	return 0;
+}
+
+int tis_sendrecv(const u8 *sendbuf, size_t send_size,
+		 u8 *recvbuf, size_t *recv_len)
+{
+	if (tis_senddata(sendbuf, send_size)) {
+		printf("%s:%d failed sending data to TPM\n",
+		       __FILE__, __LINE__);
+		return TPM_DRIVER_ERR;
+	}
+
+	return tis_readresponse(recvbuf, recv_len);
+}