tFrom 1dc5533382b9951c70b1a38f02065b41453b175a Mon Sep 17 00:00:00 2001

tFrom 1dc5533382b9951c70b1a38f02065b41453b175a Mon Sep 17 00:00:00 2001

[Stuart Yoder]

Firmware Framework for Arm A-profile (FF-A) is a messaging framework
for Arm-based systems, and in the context of the TPM CRB driver is used
to signal 'start' to a CRB-based TPM service which is hosted in an
FF-A secure partition running in TrustZone.

These patches add support for the CRB FF-A start method defined
in the TCG ACPI specification v1.4 and the FF-A ABI defined
in the Arm TPM Service CRB over FF-A (DEN0138) specification:
https://developer.arm.com/documentation/den0138/latest/

The first patch adds an FF-A driver to handle the FF-A messaging when
communicating with a CRB-based TPM secure partition built on FF-A.
The driver is probed when the TPM secure partition is discovered by
the Linux FF-A infrastructure.

The second patch consolidates the check for idle support in the CRB
driver to one place.

The third patch defines the new ACPI start method enumeration for
CRB over FF-A.

The fourth patch adds support for the FF-A ACPI start method to
the TPM crb driver.

The fifth patch adds documentation explaining how the CRB driver
and FF-A relate.

Version 8
-all changes made to patch 1:
  -fixed link error when tpm_crb was built-in and tpm_ffa_crb
   was built as module by changing IS_ENABLED() to IS_REACHABLE()
   in tpm_ffa_crb.h
  -cleaned up Kconfig definition for tpm_ffa_crb
  -added Jarkko's Reviewed-by tag
  -added ffa_tpm: to subject

Version 7
-added the tpm_ffa_crb documentation to index.rst

Version 6
-in tpm_crb removed unnecessary brackets from if statement and
 fixed comment style
-noticed and fixed bug in patch 2, polarity of return value
 from tpm_crb_has_idle() was wrong and wasn't caught in past
 testing
-added Reviewed-by tag to patches 2 and 5

Version 5
-tpm_ffa_crb patch: removed module version
-tpm_ffa_crb patch: fixed module description
-tpm_ffa_crb patch: updated comment on mutex declaration
-reworded commit message for patch 2 as per Jarkko's 
 suggestion
-added Acked tag by Sudeep to patch 1 for FF-A changes 
-added Reviewed-by tag to patches 3 and 4

Version 4
-fix warning from kernel test robot in patch 1
-fix warnings from checkpatch.pl --strict
-clean up unnecessary parenthesis usage
-update variable declaration to be reverse tree order
-document exported functions in tpm_crb_ffa driver
-remove unnecessary author and maintainer info in tpm_crb_ffa driver
-fix declaration of variables to be in reverse tree order

Version 3
-changed prefixes used throughout patch series to tpm_crb_ffa*

Version 2
-updates to cover letter to define FF-A
-added new patch with documentation
-created pull request in ACPIA and added link to the patch
 updating actbl3.h
-added tpm_ prefix to the FF-A CRB driver

Stuart Yoder (5):
  tpm_crb: ffa_tpm: implement driver compliant to CRB over FF-A
  tpm_crb: clean-up and refactor check for idle support
  ACPICA: add start method for Arm FF-A
  tpm_crb: add support for the Arm FF-A start method
  Documentation: tpm: add documentation for the CRB FF-A interface

 Documentation/security/tpm/index.rst       |   1 +
 Documentation/security/tpm/tpm_ffa_crb.rst |  65 ++++
 drivers/char/tpm/Kconfig                   |   9 +
 drivers/char/tpm/Makefile                  |   1 +
 drivers/char/tpm/tpm_crb.c                 | 105 +++++--
 drivers/char/tpm/tpm_crb_ffa.c             | 348 +++++++++++++++++++++
 drivers/char/tpm/tpm_crb_ffa.h             |  25 ++
 include/acpi/actbl3.h                      |   1 +
 8 files changed, 536 insertions(+), 19 deletions(-)
 create mode 100644 Documentation/security/tpm/tpm_ffa_crb.rst
 create mode 100644 drivers/char/tpm/tpm_crb_ffa.c
 create mode 100644 drivers/char/tpm/tpm_crb_ffa.h

-- 
2.34.1

[PATCH v8 1/5] tpm_crb: ffa_tpm: implement driver compliant to CRB over FF-A

[Stuart Yoder]

The Arm specification TPM Service CRB over FF-A specification
defines the FF-A messages to interact with a CRB-based TPM
implemented as an FF-A secure partition.

Spec URL:
https://developer.arm.com/documentation/den0138/latest/

This driver is probed when a TPM Secure Partition is
discovered by the FF-A subsystem. It exposes APIs
used by the TPM CRB driver to send notifications to
the TPM.

Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
---
 drivers/char/tpm/Kconfig       |   9 +
 drivers/char/tpm/Makefile      |   1 +
 drivers/char/tpm/tpm_crb_ffa.c | 348 +++++++++++++++++++++++++++++++++
 drivers/char/tpm/tpm_crb_ffa.h |  25 +++
 4 files changed, 383 insertions(+)
 create mode 100644 drivers/char/tpm/tpm_crb_ffa.c
 create mode 100644 drivers/char/tpm/tpm_crb_ffa.h

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index 0fc9a510e059..fe4f3a609934 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -210,6 +210,15 @@ config TCG_CRB
 	  from within Linux.  To compile this driver as a module, choose
 	  M here; the module will be called tpm_crb.
 
+config TCG_ARM_CRB_FFA
+	tristate "TPM CRB over Arm FF-A Transport"
+	depends on ARM_FFA_TRANSPORT && TCG_CRB
+	default TCG_CRB
+	help
+	  If the Arm FF-A transport is used to access the TPM say Yes.
+	  To compile this driver as a module, choose M here; the module
+	  will be called tpm_crb_ffa.
+
 config TCG_VTPM_PROXY
 	tristate "VTPM Proxy Interface"
 	depends on TCG_TPM
diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index 9bb142c75243..2b004df8c04b 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -42,5 +42,6 @@ obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
 obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
 obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
 obj-$(CONFIG_TCG_CRB) += tpm_crb.o
+obj-$(CONFIG_TCG_ARM_CRB_FFA) += tpm_crb_ffa.o
 obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
 obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c
new file mode 100644
index 000000000000..3169a87a56b6
--- /dev/null
+++ b/drivers/char/tpm/tpm_crb_ffa.c
@@ -0,0 +1,348 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Arm Ltd.
+ *
+ * This device driver implements the TPM CRB start method
+ * as defined in the TPM Service Command Response Buffer
+ * Interface Over FF-A (DEN0138).
+ */
+
+#define pr_fmt(fmt) "CRB_FFA: " fmt
+
+#include <linux/arm_ffa.h>
+#include "tpm_crb_ffa.h"
+
+/* TPM service function status codes */
+#define CRB_FFA_OK			0x05000001
+#define CRB_FFA_OK_RESULTS_RETURNED	0x05000002
+#define CRB_FFA_NOFUNC			0x8e000001
+#define CRB_FFA_NOTSUP			0x8e000002
+#define CRB_FFA_INVARG			0x8e000005
+#define CRB_FFA_INV_CRB_CTRL_DATA	0x8e000006
+#define CRB_FFA_ALREADY			0x8e000009
+#define CRB_FFA_DENIED			0x8e00000a
+#define CRB_FFA_NOMEM			0x8e00000b
+
+#define CRB_FFA_VERSION_MAJOR	1
+#define CRB_FFA_VERSION_MINOR	0
+
+/* version encoding */
+#define CRB_FFA_MAJOR_VERSION_MASK  GENMASK(30, 16)
+#define CRB_FFA_MINOR_VERSION_MASK  GENMASK(15, 0)
+#define CRB_FFA_MAJOR_VERSION(x)    ((u16)(FIELD_GET(CRB_FFA_MAJOR_VERSION_MASK, (x))))
+#define CRB_FFA_MINOR_VERSION(x)    ((u16)(FIELD_GET(CRB_FFA_MINOR_VERSION_MASK, (x))))
+
+/*
+ * Normal world sends requests with FFA_MSG_SEND_DIRECT_REQ and
+ * responses are returned with FFA_MSG_SEND_DIRECT_RESP for normal
+ * messages.
+ *
+ * All requests with FFA_MSG_SEND_DIRECT_REQ and FFA_MSG_SEND_DIRECT_RESP
+ * are using the AArch32 SMC calling convention with register usage as
+ * defined in FF-A specification:
+ * w0:    Function ID (0x8400006F or 0x84000070)
+ * w1:    Source/Destination IDs
+ * w2:    Reserved (MBZ)
+ * w3-w7: Implementation defined, free to be used below
+ */
+
+/*
+ * Returns the version of the interface that is available
+ * Call register usage:
+ * w3:    Not used (MBZ)
+ * w4:    TPM service function ID, CRB_FFA_GET_INTERFACE_VERSION
+ * w5-w7: Reserved (MBZ)
+ *
+ * Return register usage:
+ * w3:    Not used (MBZ)
+ * w4:    TPM service function status
+ * w5:    TPM service interface version
+ *        Bits[31:16]: major version
+ *        Bits[15:0]: minor version
+ * w6-w7: Reserved (MBZ)
+ *
+ * Possible function status codes in register w4:
+ *     CRB_FFA_OK_RESULTS_RETURNED: The version of the interface has been
+ *                                  returned.
+ */
+#define CRB_FFA_GET_INTERFACE_VERSION 0x0f000001
+
+/*
+ * Return information on a given feature of the TPM service
+ * Call register usage:
+ * w3:    Not used (MBZ)
+ * w4:    TPM service function ID, CRB_FFA_START
+ * w5:    Start function qualifier
+ *            Bits[31:8] (MBZ)
+ *            Bits[7:0]
+ *              0: Notifies TPM that a command is ready to be processed
+ *              1: Notifies TPM that a locality request is ready to be processed
+ * w6:    TPM locality, one of 0..4
+ *            -If the start function qualifier is 0, identifies the locality
+ *             from where the command originated.
+ *            -If the start function qualifier is 1, identifies the locality
+ *             of the locality request
+ * w6-w7: Reserved (MBZ)
+ *
+ * Return register usage:
+ * w3:    Not used (MBZ)
+ * w4:    TPM service function status
+ * w5-w7: Reserved (MBZ)
+ *
+ * Possible function status codes in register w4:
+ *     CRB_FFA_OK: the TPM service has been notified successfully
+ *     CRB_FFA_INVARG: one or more arguments are not valid
+ *     CRB_FFA_INV_CRB_CTRL_DATA: CRB control data or locality control
+ *         data at the given TPM locality is not valid
+ *     CRB_FFA_DENIED: the TPM has previously disabled locality requests and
+ *         command processing at the given locality
+ */
+#define CRB_FFA_START 0x0f000201
+
+struct tpm_crb_ffa {
+	struct ffa_device *ffa_dev;
+	u16 major_version;
+	u16 minor_version;
+	/* lock to protect sending of FF-A messages: */
+	struct mutex msg_data_lock;
+	struct ffa_send_direct_data direct_msg_data;
+};
+
+static struct tpm_crb_ffa *tpm_crb_ffa;
+
+static int tpm_crb_ffa_to_linux_errno(int errno)
+{
+	int rc;
+
+	switch (errno) {
+	case CRB_FFA_OK:
+		rc = 0;
+		break;
+	case CRB_FFA_OK_RESULTS_RETURNED:
+		rc = 0;
+		break;
+	case CRB_FFA_NOFUNC:
+		rc = -ENOENT;
+		break;
+	case CRB_FFA_NOTSUP:
+		rc = -EPERM;
+		break;
+	case CRB_FFA_INVARG:
+		rc = -EINVAL;
+		break;
+	case CRB_FFA_INV_CRB_CTRL_DATA:
+		rc = -ENOEXEC;
+		break;
+	case CRB_FFA_ALREADY:
+		rc = -EEXIST;
+		break;
+	case CRB_FFA_DENIED:
+		rc = -EACCES;
+		break;
+	case CRB_FFA_NOMEM:
+		rc = -ENOMEM;
+		break;
+	default:
+		rc = -EINVAL;
+	}
+
+	return rc;
+}
+
+/**
+ * tpm_crb_ffa_init - called by the CRB driver to do any needed initialization
+ *
+ * This function is called by the tpm_crb driver during the tpm_crb
+ * driver's initialization. If the tpm_crb_ffa has not been probed
+ * yet, returns -ENOENT in order to force a retry.  If th ffa_crb
+ * driver had been probed  but failed with an error, returns -ENODEV
+ * in order to prevent further retries.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int tpm_crb_ffa_init(void)
+{
+	if (!tpm_crb_ffa)
+		return -ENOENT;
+
+	if (IS_ERR_VALUE(tpm_crb_ffa))
+		return -ENODEV;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);
+
+static int __tpm_crb_ffa_send_recieve(unsigned long func_id,
+				      unsigned long a0,
+				      unsigned long a1,
+				      unsigned long a2)
+{
+	const struct ffa_msg_ops *msg_ops;
+	int ret;
+
+	if (!tpm_crb_ffa)
+		return -ENOENT;
+
+	msg_ops = tpm_crb_ffa->ffa_dev->ops->msg_ops;
+
+	memset(&tpm_crb_ffa->direct_msg_data, 0x00,
+	       sizeof(struct ffa_send_direct_data));
+
+	tpm_crb_ffa->direct_msg_data.data1 = func_id;
+	tpm_crb_ffa->direct_msg_data.data2 = a0;
+	tpm_crb_ffa->direct_msg_data.data3 = a1;
+	tpm_crb_ffa->direct_msg_data.data4 = a2;
+
+	ret = msg_ops->sync_send_receive(tpm_crb_ffa->ffa_dev,
+			&tpm_crb_ffa->direct_msg_data);
+	if (!ret)
+		ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data.data1);
+
+	return ret;
+}
+
+/**
+ * tpm_crb_ffa_get_interface_version() - gets the ABI version of the TPM service
+ * @major: Pointer to caller-allocated buffer to hold the major version
+ *         number the ABI
+ * @minor: Pointer to caller-allocated buffer to hold the minor version
+ *         number the ABI
+ *
+ * Returns the major and minor version of the ABI of the FF-A based TPM.
+ * Allows the caller to evaluate its compatibility with the version of
+ * the ABI.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int tpm_crb_ffa_get_interface_version(u16 *major, u16 *minor)
+{
+	int rc;
+
+	if (!tpm_crb_ffa)
+		return -ENOENT;
+
+	if (IS_ERR_VALUE(tpm_crb_ffa))
+		return -ENODEV;
+
+	if (!major || !minor)
+		return -EINVAL;
+
+	guard(mutex)(&tpm_crb_ffa->msg_data_lock);
+
+	rc = __tpm_crb_ffa_send_recieve(CRB_FFA_GET_INTERFACE_VERSION, 0x00, 0x00, 0x00);
+	if (!rc) {
+		*major = CRB_FFA_MAJOR_VERSION(tpm_crb_ffa->direct_msg_data.data2);
+		*minor = CRB_FFA_MINOR_VERSION(tpm_crb_ffa->direct_msg_data.data2);
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(tpm_crb_ffa_get_interface_version);
+
+/**
+ * tpm_crb_ffa_start() - signals the TPM that a field has changed in the CRB
+ * @request_type: Identifies whether the change to the CRB is in the command
+ *                fields or locality fields.
+ * @locality: Specifies the locality number.
+ *
+ * Used by the CRB driver
+ * that might be useful to those using or modifying it.  Begins with
+ * empty comment line, and may include additional embedded empty
+ * comment lines.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int tpm_crb_ffa_start(int request_type, int locality)
+{
+	if (!tpm_crb_ffa)
+		return -ENOENT;
+
+	if (IS_ERR_VALUE(tpm_crb_ffa))
+		return -ENODEV;
+
+	guard(mutex)(&tpm_crb_ffa->msg_data_lock);
+
+	return __tpm_crb_ffa_send_recieve(CRB_FFA_START, request_type, locality, 0x00);
+}
+EXPORT_SYMBOL_GPL(tpm_crb_ffa_start);
+
+static int tpm_crb_ffa_probe(struct ffa_device *ffa_dev)
+{
+	struct tpm_crb_ffa *p;
+	int rc;
+
+	/* only one instance of a TPM partition is supported */
+	if (tpm_crb_ffa && !IS_ERR_VALUE(tpm_crb_ffa))
+		return -EEXIST;
+
+	tpm_crb_ffa = ERR_PTR(-ENODEV); // set tpm_crb_ffa so we can detect probe failure
+
+	if (!ffa_partition_supports_direct_recv(ffa_dev)) {
+		pr_err("TPM partition doesn't support direct message receive.\n");
+		return -EINVAL;
+	}
+
+	p = kzalloc(sizeof(*tpm_crb_ffa), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+	tpm_crb_ffa = p;
+
+	mutex_init(&tpm_crb_ffa->msg_data_lock);
+	tpm_crb_ffa->ffa_dev = ffa_dev;
+	ffa_dev_set_drvdata(ffa_dev, tpm_crb_ffa);
+
+	/* if TPM is aarch32 use 32-bit SMCs */
+	if (!ffa_partition_check_property(ffa_dev, FFA_PARTITION_AARCH64_EXEC))
+		ffa_dev->ops->msg_ops->mode_32bit_set(ffa_dev);
+
+	/* verify compatibility of TPM service version number */
+	rc = tpm_crb_ffa_get_interface_version(&tpm_crb_ffa->major_version,
+					       &tpm_crb_ffa->minor_version);
+	if (rc) {
+		pr_err("failed to get crb interface version. rc:%d", rc);
+		goto out;
+	}
+
+	pr_info("ABI version %u.%u", tpm_crb_ffa->major_version,
+		tpm_crb_ffa->minor_version);
+
+	if (tpm_crb_ffa->major_version != CRB_FFA_VERSION_MAJOR ||
+	    (tpm_crb_ffa->minor_version > 0 &&
+	    tpm_crb_ffa->minor_version < CRB_FFA_VERSION_MINOR)) {
+		pr_err("Incompatible ABI version");
+		goto out;
+	}
+
+	return 0;
+
+out:
+	kfree(tpm_crb_ffa);
+	tpm_crb_ffa = ERR_PTR(-ENODEV);
+	return -EINVAL;
+}
+
+static void tpm_crb_ffa_remove(struct ffa_device *ffa_dev)
+{
+	kfree(tpm_crb_ffa);
+	tpm_crb_ffa = NULL;
+}
+
+static const struct ffa_device_id tpm_crb_ffa_device_id[] = {
+	/* 17b862a4-1806-4faf-86b3-089a58353861 */
+	{ UUID_INIT(0x17b862a4, 0x1806, 0x4faf,
+		    0x86, 0xb3, 0x08, 0x9a, 0x58, 0x35, 0x38, 0x61) },
+	{}
+};
+
+static struct ffa_driver tpm_crb_ffa_driver = {
+	.name = "ffa-crb",
+	.probe = tpm_crb_ffa_probe,
+	.remove = tpm_crb_ffa_remove,
+	.id_table = tpm_crb_ffa_device_id,
+};
+
+module_ffa_driver(tpm_crb_ffa_driver);
+
+MODULE_AUTHOR("Arm");
+MODULE_DESCRIPTION("TPM CRB FFA driver");
+MODULE_LICENSE("GPL");
diff --git a/drivers/char/tpm/tpm_crb_ffa.h b/drivers/char/tpm/tpm_crb_ffa.h
new file mode 100644
index 000000000000..645c41ede10e
--- /dev/null
+++ b/drivers/char/tpm/tpm_crb_ffa.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2024 Arm Ltd.
+ *
+ * This device driver implements the TPM CRB start method
+ * as defined in the TPM Service Command Response Buffer
+ * Interface Over FF-A (DEN0138).
+ */
+#ifndef _TPM_CRB_FFA_H
+#define _TPM_CRB_FFA_H
+
+#if IS_REACHABLE(CONFIG_TCG_ARM_CRB_FFA)
+int tpm_crb_ffa_init(void);
+int tpm_crb_ffa_get_interface_version(u16 *major, u16 *minor);
+int tpm_crb_ffa_start(int request_type, int locality);
+#else
+static inline int tpm_crb_ffa_init(void) { return 0; }
+static inline int tpm_crb_ffa_get_interface_version(u16 *major, u16 *minor) { return 0; }
+static inline int tpm_crb_ffa_start(int request_type, int locality) { return 0; }
+#endif
+
+#define CRB_FFA_START_TYPE_COMMAND 0
+#define CRB_FFA_START_TYPE_LOCALITY_REQUEST 1
+
+#endif
-- 
2.34.1

[PATCH v8 2/5] tpm_crb: clean-up and refactor check for idle support

[Stuart Yoder]

Refactor TPM idle check to tpm_crb_has_idle(), and reduce paraentheses
usage in start method checks

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
---
 drivers/char/tpm/tpm_crb.c | 36 +++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index ea085b14ab7c..c6898710a66b 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -115,6 +115,16 @@ struct tpm2_crb_pluton {
 	u64 reply_addr;
 };
 
+/*
+ * Returns true if the start method supports idle.
+ */
+static inline bool tpm_crb_has_idle(u32 start_method)
+{
+	return !(start_method == ACPI_TPM2_START_METHOD ||
+	       start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD ||
+	       start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC);
+}
+
 static bool crb_wait_for_reg_32(u32 __iomem *reg, u32 mask, u32 value,
 				unsigned long timeout)
 {
@@ -173,9 +183,7 @@ static int __crb_go_idle(struct device *dev, struct crb_priv *priv)
 {
 	int rc;
 
-	if ((priv->sm == ACPI_TPM2_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
+	if (!tpm_crb_has_idle(priv->sm))
 		return 0;
 
 	iowrite32(CRB_CTRL_REQ_GO_IDLE, &priv->regs_t->ctrl_req);
@@ -222,9 +230,7 @@ static int __crb_cmd_ready(struct device *dev, struct crb_priv *priv)
 {
 	int rc;
 
-	if ((priv->sm == ACPI_TPM2_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
+	if (!tpm_crb_has_idle(priv->sm))
 		return 0;
 
 	iowrite32(CRB_CTRL_REQ_CMD_READY, &priv->regs_t->ctrl_req);
@@ -423,13 +429,13 @@ static int crb_send(struct tpm_chip *chip, u8 *buf, size_t len)
 	 * report only ACPI start but in practice seems to require both
 	 * CRB start, hence invoking CRB start method if hid == MSFT0101.
 	 */
-	if ((priv->sm == ACPI_TPM2_COMMAND_BUFFER) ||
-	    (priv->sm == ACPI_TPM2_MEMORY_MAPPED) ||
-	    (!strcmp(priv->hid, "MSFT0101")))
+	if (priv->sm == ACPI_TPM2_COMMAND_BUFFER ||
+	    priv->sm == ACPI_TPM2_MEMORY_MAPPED ||
+	    !strcmp(priv->hid, "MSFT0101"))
 		iowrite32(CRB_START_INVOKE, &priv->regs_t->ctrl_start);
 
-	if ((priv->sm == ACPI_TPM2_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD))
+	if (priv->sm == ACPI_TPM2_START_METHOD ||
+	    priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD)
 		rc = crb_do_acpi_start(chip);
 
 	if (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC) {
@@ -449,8 +455,8 @@ static void crb_cancel(struct tpm_chip *chip)
 
 	iowrite32(CRB_CANCEL_INVOKE, &priv->regs_t->ctrl_cancel);
 
-	if (((priv->sm == ACPI_TPM2_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD)) &&
+	if ((priv->sm == ACPI_TPM2_START_METHOD ||
+	     priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) &&
 	     crb_do_acpi_start(chip))
 		dev_err(&chip->dev, "ACPI Start failed\n");
 }
@@ -609,8 +615,8 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 	 * the control area, as one nice sane region except for some older
 	 * stuff that puts the control area outside the ACPI IO region.
 	 */
-	if ((priv->sm == ACPI_TPM2_COMMAND_BUFFER) ||
-	    (priv->sm == ACPI_TPM2_MEMORY_MAPPED)) {
+	if (priv->sm == ACPI_TPM2_COMMAND_BUFFER ||
+	    priv->sm == ACPI_TPM2_MEMORY_MAPPED) {
 		if (iores &&
 		    buf->control_address == iores->start +
 		    sizeof(*priv->regs_h))
-- 
2.34.1

[PATCH v8 3/5] ACPICA: add start method for Arm FF-A

[Stuart Yoder]

Add TPM start method for Arm FF-A defined in the TCG ACPI
specification v1.4.

Link: https://github.com/acpica/acpica/pull/1000
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
---
 include/acpi/actbl3.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/acpi/actbl3.h b/include/acpi/actbl3.h
index 5cd755143b7d..a97b1dbab975 100644
--- a/include/acpi/actbl3.h
+++ b/include/acpi/actbl3.h
@@ -466,6 +466,7 @@ struct acpi_tpm2_phy {
 #define ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC       11	/* V1.2 Rev 8 */
 #define ACPI_TPM2_RESERVED                          12
 #define ACPI_TPM2_COMMAND_BUFFER_WITH_PLUTON        13
+#define ACPI_TPM2_CRB_WITH_ARM_FFA                  15
 
 /* Optional trailer appears after any start_method subtables */
 
-- 
2.34.1

[PATCH v8 4/5] tpm_crb: add support for the Arm FF-A start method

[Stuart Yoder]

The TCG ACPI spec v1.4 defines a start method for the
TPMs implemented with the Arm CRB over FF-A ABI.

Add support for the FF-A start method, and use interfaces
provided by the ffa_crb driver to interact with the
FF-A based TPM.

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
---
 drivers/char/tpm/tpm_crb.c | 71 +++++++++++++++++++++++++++++++++++---
 1 file changed, 66 insertions(+), 5 deletions(-)

diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index c6898710a66b..876edf2705ab 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -19,6 +19,7 @@
 #ifdef CONFIG_ARM64
 #include <linux/arm-smccc.h>
 #endif
+#include "tpm_crb_ffa.h"
 #include "tpm.h"
 
 #define ACPI_SIG_TPM2 "TPM2"
@@ -100,6 +101,8 @@ struct crb_priv {
 	u32 smc_func_id;
 	u32 __iomem *pluton_start_addr;
 	u32 __iomem *pluton_reply_addr;
+	u8 ffa_flags;
+	u8 ffa_attributes;
 };
 
 struct tpm2_crb_smc {
@@ -110,6 +113,14 @@ struct tpm2_crb_smc {
 	u32 smc_func_id;
 };
 
+/* CRB over FFA start method parameters in TCG2 ACPI table */
+struct tpm2_crb_ffa {
+	u8 flags;
+	u8 attributes;
+	u16 partition_id;
+	u8 reserved[8];
+};
+
 struct tpm2_crb_pluton {
 	u64 start_addr;
 	u64 reply_addr;
@@ -122,7 +133,8 @@ static inline bool tpm_crb_has_idle(u32 start_method)
 {
 	return !(start_method == ACPI_TPM2_START_METHOD ||
 	       start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD ||
-	       start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC);
+	       start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC ||
+	       start_method == ACPI_TPM2_CRB_WITH_ARM_FFA);
 }
 
 static bool crb_wait_for_reg_32(u32 __iomem *reg, u32 mask, u32 value,
@@ -261,13 +273,20 @@ static int crb_cmd_ready(struct tpm_chip *chip)
 static int __crb_request_locality(struct device *dev,
 				  struct crb_priv *priv, int loc)
 {
-	u32 value = CRB_LOC_STATE_LOC_ASSIGNED |
-		    CRB_LOC_STATE_TPM_REG_VALID_STS;
+	u32 value = CRB_LOC_STATE_LOC_ASSIGNED | CRB_LOC_STATE_TPM_REG_VALID_STS;
+	int rc;
 
 	if (!priv->regs_h)
 		return 0;
 
 	iowrite32(CRB_LOC_CTRL_REQUEST_ACCESS, &priv->regs_h->loc_ctrl);
+
+	if (priv->sm == ACPI_TPM2_CRB_WITH_ARM_FFA) {
+		rc = tpm_crb_ffa_start(CRB_FFA_START_TYPE_LOCALITY_REQUEST, loc);
+		if (rc)
+			return rc;
+	}
+
 	if (!crb_wait_for_reg_32(&priv->regs_h->loc_state, value, value,
 				 TPM2_TIMEOUT_C)) {
 		dev_warn(dev, "TPM_LOC_STATE_x.requestAccess timed out\n");
@@ -287,14 +306,21 @@ static int crb_request_locality(struct tpm_chip *chip, int loc)
 static int __crb_relinquish_locality(struct device *dev,
 				     struct crb_priv *priv, int loc)
 {
-	u32 mask = CRB_LOC_STATE_LOC_ASSIGNED |
-		   CRB_LOC_STATE_TPM_REG_VALID_STS;
+	u32 mask = CRB_LOC_STATE_LOC_ASSIGNED | CRB_LOC_STATE_TPM_REG_VALID_STS;
 	u32 value = CRB_LOC_STATE_TPM_REG_VALID_STS;
+	int rc;
 
 	if (!priv->regs_h)
 		return 0;
 
 	iowrite32(CRB_LOC_CTRL_RELINQUISH, &priv->regs_h->loc_ctrl);
+
+	if (priv->sm == ACPI_TPM2_CRB_WITH_ARM_FFA) {
+		rc = tpm_crb_ffa_start(CRB_FFA_START_TYPE_LOCALITY_REQUEST, loc);
+		if (rc)
+			return rc;
+	}
+
 	if (!crb_wait_for_reg_32(&priv->regs_h->loc_state, mask, value,
 				 TPM2_TIMEOUT_C)) {
 		dev_warn(dev, "TPM_LOC_STATE_x.Relinquish timed out\n");
@@ -443,6 +469,11 @@ static int crb_send(struct tpm_chip *chip, u8 *buf, size_t len)
 		rc = tpm_crb_smc_start(&chip->dev, priv->smc_func_id);
 	}
 
+	if (priv->sm == ACPI_TPM2_CRB_WITH_ARM_FFA) {
+		iowrite32(CRB_START_INVOKE, &priv->regs_t->ctrl_start);
+		rc = tpm_crb_ffa_start(CRB_FFA_START_TYPE_COMMAND, chip->locality);
+	}
+
 	if (rc)
 		return rc;
 
@@ -452,6 +483,7 @@ static int crb_send(struct tpm_chip *chip, u8 *buf, size_t len)
 static void crb_cancel(struct tpm_chip *chip)
 {
 	struct crb_priv *priv = dev_get_drvdata(&chip->dev);
+	int rc;
 
 	iowrite32(CRB_CANCEL_INVOKE, &priv->regs_t->ctrl_cancel);
 
@@ -459,6 +491,12 @@ static void crb_cancel(struct tpm_chip *chip)
 	     priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) &&
 	     crb_do_acpi_start(chip))
 		dev_err(&chip->dev, "ACPI Start failed\n");
+
+	if (priv->sm == ACPI_TPM2_CRB_WITH_ARM_FFA) {
+		rc = tpm_crb_ffa_start(CRB_FFA_START_TYPE_COMMAND, chip->locality);
+		if (rc)
+			dev_err(&chip->dev, "FF-A Start failed\n");
+	}
 }
 
 static bool crb_req_canceled(struct tpm_chip *chip, u8 status)
@@ -616,6 +654,7 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 	 * stuff that puts the control area outside the ACPI IO region.
 	 */
 	if (priv->sm == ACPI_TPM2_COMMAND_BUFFER ||
+	    priv->sm == ACPI_TPM2_CRB_WITH_ARM_FFA ||
 	    priv->sm == ACPI_TPM2_MEMORY_MAPPED) {
 		if (iores &&
 		    buf->control_address == iores->start +
@@ -737,6 +776,7 @@ static int crb_acpi_add(struct acpi_device *device)
 	struct tpm_chip *chip;
 	struct device *dev = &device->dev;
 	struct tpm2_crb_smc *crb_smc;
+	struct tpm2_crb_ffa *crb_ffa;
 	struct tpm2_crb_pluton *crb_pluton;
 	acpi_status status;
 	u32 sm;
@@ -775,6 +815,27 @@ static int crb_acpi_add(struct acpi_device *device)
 		priv->smc_func_id = crb_smc->smc_func_id;
 	}
 
+	if (sm == ACPI_TPM2_CRB_WITH_ARM_FFA) {
+		if (buf->header.length < (sizeof(*buf) + sizeof(*crb_ffa))) {
+			dev_err(dev,
+				FW_BUG "TPM2 ACPI table has wrong size %u for start method type %d\n",
+				buf->header.length,
+				ACPI_TPM2_CRB_WITH_ARM_FFA);
+			rc = -EINVAL;
+			goto out;
+		}
+		crb_ffa = ACPI_ADD_PTR(struct tpm2_crb_ffa, buf, sizeof(*buf));
+		priv->ffa_flags = crb_ffa->flags;
+		priv->ffa_attributes = crb_ffa->attributes;
+		rc = tpm_crb_ffa_init();
+		if (rc) {
+			/* If FF-A driver is not available yet, request probe retry */
+			if (rc == -ENOENT)
+				rc = -EPROBE_DEFER;
+			goto out;
+		}
+	}
+
 	if (sm == ACPI_TPM2_COMMAND_BUFFER_WITH_PLUTON) {
 		if (buf->header.length < (sizeof(*buf) + sizeof(*crb_pluton))) {
 			dev_err(dev,
-- 
2.34.1

[PATCH v8 5/5] Documentation: tpm: add documentation for the CRB FF-A interface

[Stuart Yoder]

Add documentation providing details of how the CRB driver interacts
with FF-A.

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
---
 Documentation/security/tpm/index.rst       |  1 +
 Documentation/security/tpm/tpm_ffa_crb.rst | 65 ++++++++++++++++++++++
 2 files changed, 66 insertions(+)
 create mode 100644 Documentation/security/tpm/tpm_ffa_crb.rst

diff --git a/Documentation/security/tpm/index.rst b/Documentation/security/tpm/index.rst
index fa593d960040..deda952eacbe 100644
--- a/Documentation/security/tpm/index.rst
+++ b/Documentation/security/tpm/index.rst
@@ -10,3 +10,4 @@ Trusted Platform Module documentation
    tpm_vtpm_proxy
    xen-tpmfront
    tpm_ftpm_tee
+   tpm_ffa_crb
diff --git a/Documentation/security/tpm/tpm_ffa_crb.rst b/Documentation/security/tpm/tpm_ffa_crb.rst
new file mode 100644
index 000000000000..0184193da3c7
--- /dev/null
+++ b/Documentation/security/tpm/tpm_ffa_crb.rst
@@ -0,0 +1,65 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================
+TPM CRB over FF-A Driver
+========================
+
+The TPM Command Response Buffer (CRB) interface is a standard TPM interface
+defined in the TCG PC Client Platform TPM Profile (PTP) Specification [1]_.
+The CRB provides a structured set of control registers a client uses when
+interacting with a TPM as well as a data buffer for storing TPM commands and
+responses. A CRB interface can be implemented in:
+
+- hardware registers in a discrete TPM chip
+
+- in memory for a TPM running in isolated environment where shared memory
+  allows a client to interact with the TPM
+
+The Firmware Framework for Arm A-profile (FF-A) [2]_ is a specification
+that defines interfaces and protocols for the following purposes:
+
+- Compartmentalize firmware into software partitions that run in the Arm
+  Secure world environment (also know as TrustZone)
+
+- Provide a standard interface for software components in the Non-secure
+  state, for example OS and Hypervisors, to communicate with this firmware.
+
+A TPM can be implemented as an FF-A secure service.  This could be a firmware
+TPM or could potentially be a TPM service that acts as a proxy to a discrete
+TPM chip. An FF-A based TPM abstracts hardware details (e.g. bus controller
+and chip selects) away from the OS and can protect locality 4 from access
+by an OS.  The TCG-defined CRB interface is used by clients to interact
+with the TPM service.
+
+The Arm TPM Service Command Response Buffer Interface Over FF-A [3]_
+specification defines FF-A messages that can be used by a client to signal
+when updates have been made to the CRB.
+
+How the Linux CRB driver interacts with FF-A is summarized below:
+
+- The tpm_crb_ffa driver registers with the FF-A subsystem in the kernel
+  with an architected TPM service UUID defined in the CRB over FF-A spec.
+
+- If a TPM service is discovered by FF-A, the probe() function in the
+  tpm_crb_ffa driver runs, and the driver initializes.
+
+- The probing and initialization of the Linux CRB driver is triggered
+  by the discovery of a TPM advertised via ACPI.  The CRB driver can
+  detect the type of TPM through the ACPI 'start' method.  The start
+  method for Arm FF-A was defined in TCG ACPI v1.4 [4]_.
+
+- When the CRB driver performs its normal functions such as signaling 'start'
+  and locality request/relinquish it invokes the tpm_crb_ffa_start() funnction
+  in the tpm_crb_ffa driver which handles the FF-A messaging to the TPM.
+
+References
+==========
+
+.. [1] **TCG PC Client Platform TPM Profile (PTP) Specification**
+   https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
+.. [2] **Arm Firmware Framework for Arm A-profile (FF-A)**
+   https://developer.arm.com/documentation/den0077/latest/
+.. [3] **Arm TPM Service Command Response Buffer Interface Over FF-A**
+   https://developer.arm.com/documentation/den0138/latest/
+.. [4] **TCG ACPI Specification**
+   https://trustedcomputinggroup.org/resource/tcg-acpi-specification/
-- 
2.34.1

Re: [PATCH v8 1/5] tpm_crb: ffa_tpm: implement driver compliant to CRB over FF-A

[Jarkko Sakkinen]

On Wed, Mar 12, 2025 at 04:58:24PM -0500, Stuart Yoder wrote:
> The Arm specification TPM Service CRB over FF-A specification
> defines the FF-A messages to interact with a CRB-based TPM
> implemented as an FF-A secure partition.
> 
> Spec URL:
> https://developer.arm.com/documentation/den0138/latest/
> 
> This driver is probed when a TPM Secure Partition is
> discovered by the FF-A subsystem. It exposes APIs
> used by the TPM CRB driver to send notifications to
> the TPM.
> 
> Acked-by: Sudeep Holla <sudeep.holla@arm.com>
> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

nit: should have been removed given the build issue (to make
apparent the need for review).

> Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
> ---
>  drivers/char/tpm/Kconfig       |   9 +
>  drivers/char/tpm/Makefile      |   1 +
>  drivers/char/tpm/tpm_crb_ffa.c | 348 +++++++++++++++++++++++++++++++++
>  drivers/char/tpm/tpm_crb_ffa.h |  25 +++
>  4 files changed, 383 insertions(+)
>  create mode 100644 drivers/char/tpm/tpm_crb_ffa.c
>  create mode 100644 drivers/char/tpm/tpm_crb_ffa.h
> 
> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index 0fc9a510e059..fe4f3a609934 100644
> --- a/drivers/char/tpm/Kconfig
> +++ b/drivers/char/tpm/Kconfig
> @@ -210,6 +210,15 @@ config TCG_CRB
>  	  from within Linux.  To compile this driver as a module, choose
>  	  M here; the module will be called tpm_crb.
>  
> +config TCG_ARM_CRB_FFA
> +	tristate "TPM CRB over Arm FF-A Transport"
> +	depends on ARM_FFA_TRANSPORT && TCG_CRB
> +	default TCG_CRB
> +	help
> +	  If the Arm FF-A transport is used to access the TPM say Yes.
> +	  To compile this driver as a module, choose M here; the module
> +	  will be called tpm_crb_ffa.
> +
>  config TCG_VTPM_PROXY
>  	tristate "VTPM Proxy Interface"
>  	depends on TCG_TPM
> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> index 9bb142c75243..2b004df8c04b 100644
> --- a/drivers/char/tpm/Makefile
> +++ b/drivers/char/tpm/Makefile
> @@ -42,5 +42,6 @@ obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
>  obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
>  obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
>  obj-$(CONFIG_TCG_CRB) += tpm_crb.o
> +obj-$(CONFIG_TCG_ARM_CRB_FFA) += tpm_crb_ffa.o
>  obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
>  obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
> diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c
> new file mode 100644
> index 000000000000..3169a87a56b6
> --- /dev/null
> +++ b/drivers/char/tpm/tpm_crb_ffa.c
> @@ -0,0 +1,348 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2024 Arm Ltd.
> + *
> + * This device driver implements the TPM CRB start method
> + * as defined in the TPM Service Command Response Buffer
> + * Interface Over FF-A (DEN0138).
> + */
> +
> +#define pr_fmt(fmt) "CRB_FFA: " fmt
> +
> +#include <linux/arm_ffa.h>
> +#include "tpm_crb_ffa.h"
> +
> +/* TPM service function status codes */
> +#define CRB_FFA_OK			0x05000001
> +#define CRB_FFA_OK_RESULTS_RETURNED	0x05000002
> +#define CRB_FFA_NOFUNC			0x8e000001
> +#define CRB_FFA_NOTSUP			0x8e000002
> +#define CRB_FFA_INVARG			0x8e000005
> +#define CRB_FFA_INV_CRB_CTRL_DATA	0x8e000006
> +#define CRB_FFA_ALREADY			0x8e000009
> +#define CRB_FFA_DENIED			0x8e00000a
> +#define CRB_FFA_NOMEM			0x8e00000b
> +
> +#define CRB_FFA_VERSION_MAJOR	1
> +#define CRB_FFA_VERSION_MINOR	0
> +
> +/* version encoding */
> +#define CRB_FFA_MAJOR_VERSION_MASK  GENMASK(30, 16)
> +#define CRB_FFA_MINOR_VERSION_MASK  GENMASK(15, 0)
> +#define CRB_FFA_MAJOR_VERSION(x)    ((u16)(FIELD_GET(CRB_FFA_MAJOR_VERSION_MASK, (x))))
> +#define CRB_FFA_MINOR_VERSION(x)    ((u16)(FIELD_GET(CRB_FFA_MINOR_VERSION_MASK, (x))))
> +
> +/*
> + * Normal world sends requests with FFA_MSG_SEND_DIRECT_REQ and
> + * responses are returned with FFA_MSG_SEND_DIRECT_RESP for normal
> + * messages.
> + *
> + * All requests with FFA_MSG_SEND_DIRECT_REQ and FFA_MSG_SEND_DIRECT_RESP
> + * are using the AArch32 SMC calling convention with register usage as
> + * defined in FF-A specification:
> + * w0:    Function ID (0x8400006F or 0x84000070)
> + * w1:    Source/Destination IDs
> + * w2:    Reserved (MBZ)
> + * w3-w7: Implementation defined, free to be used below
> + */
> +
> +/*
> + * Returns the version of the interface that is available
> + * Call register usage:
> + * w3:    Not used (MBZ)
> + * w4:    TPM service function ID, CRB_FFA_GET_INTERFACE_VERSION
> + * w5-w7: Reserved (MBZ)
> + *
> + * Return register usage:
> + * w3:    Not used (MBZ)
> + * w4:    TPM service function status
> + * w5:    TPM service interface version
> + *        Bits[31:16]: major version
> + *        Bits[15:0]: minor version
> + * w6-w7: Reserved (MBZ)
> + *
> + * Possible function status codes in register w4:
> + *     CRB_FFA_OK_RESULTS_RETURNED: The version of the interface has been
> + *                                  returned.
> + */
> +#define CRB_FFA_GET_INTERFACE_VERSION 0x0f000001
> +
> +/*
> + * Return information on a given feature of the TPM service
> + * Call register usage:
> + * w3:    Not used (MBZ)
> + * w4:    TPM service function ID, CRB_FFA_START
> + * w5:    Start function qualifier
> + *            Bits[31:8] (MBZ)
> + *            Bits[7:0]
> + *              0: Notifies TPM that a command is ready to be processed
> + *              1: Notifies TPM that a locality request is ready to be processed
> + * w6:    TPM locality, one of 0..4
> + *            -If the start function qualifier is 0, identifies the locality
> + *             from where the command originated.
> + *            -If the start function qualifier is 1, identifies the locality
> + *             of the locality request
> + * w6-w7: Reserved (MBZ)
> + *
> + * Return register usage:
> + * w3:    Not used (MBZ)
> + * w4:    TPM service function status
> + * w5-w7: Reserved (MBZ)
> + *
> + * Possible function status codes in register w4:
> + *     CRB_FFA_OK: the TPM service has been notified successfully
> + *     CRB_FFA_INVARG: one or more arguments are not valid
> + *     CRB_FFA_INV_CRB_CTRL_DATA: CRB control data or locality control
> + *         data at the given TPM locality is not valid
> + *     CRB_FFA_DENIED: the TPM has previously disabled locality requests and
> + *         command processing at the given locality
> + */
> +#define CRB_FFA_START 0x0f000201
> +
> +struct tpm_crb_ffa {
> +	struct ffa_device *ffa_dev;
> +	u16 major_version;
> +	u16 minor_version;
> +	/* lock to protect sending of FF-A messages: */
> +	struct mutex msg_data_lock;
> +	struct ffa_send_direct_data direct_msg_data;
> +};
> +
> +static struct tpm_crb_ffa *tpm_crb_ffa;
> +
> +static int tpm_crb_ffa_to_linux_errno(int errno)
> +{
> +	int rc;
> +
> +	switch (errno) {
> +	case CRB_FFA_OK:
> +		rc = 0;
> +		break;
> +	case CRB_FFA_OK_RESULTS_RETURNED:
> +		rc = 0;
> +		break;
> +	case CRB_FFA_NOFUNC:
> +		rc = -ENOENT;
> +		break;
> +	case CRB_FFA_NOTSUP:
> +		rc = -EPERM;
> +		break;
> +	case CRB_FFA_INVARG:
> +		rc = -EINVAL;
> +		break;
> +	case CRB_FFA_INV_CRB_CTRL_DATA:
> +		rc = -ENOEXEC;
> +		break;
> +	case CRB_FFA_ALREADY:
> +		rc = -EEXIST;
> +		break;
> +	case CRB_FFA_DENIED:
> +		rc = -EACCES;
> +		break;
> +	case CRB_FFA_NOMEM:
> +		rc = -ENOMEM;
> +		break;
> +	default:
> +		rc = -EINVAL;
> +	}
> +
> +	return rc;
> +}
> +
> +/**
> + * tpm_crb_ffa_init - called by the CRB driver to do any needed initialization
> + *
> + * This function is called by the tpm_crb driver during the tpm_crb
> + * driver's initialization. If the tpm_crb_ffa has not been probed
> + * yet, returns -ENOENT in order to force a retry.  If th ffa_crb
> + * driver had been probed  but failed with an error, returns -ENODEV
> + * in order to prevent further retries.
> + *
> + * Return: 0 on success, negative error code on failure.
> + */
> +int tpm_crb_ffa_init(void)
> +{
> +	if (!tpm_crb_ffa)
> +		return -ENOENT;
> +
> +	if (IS_ERR_VALUE(tpm_crb_ffa))
> +		return -ENODEV;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);
> +
> +static int __tpm_crb_ffa_send_recieve(unsigned long func_id,
> +				      unsigned long a0,
> +				      unsigned long a1,
> +				      unsigned long a2)
> +{
> +	const struct ffa_msg_ops *msg_ops;
> +	int ret;
> +
> +	if (!tpm_crb_ffa)
> +		return -ENOENT;
> +
> +	msg_ops = tpm_crb_ffa->ffa_dev->ops->msg_ops;
> +
> +	memset(&tpm_crb_ffa->direct_msg_data, 0x00,
> +	       sizeof(struct ffa_send_direct_data));
> +
> +	tpm_crb_ffa->direct_msg_data.data1 = func_id;
> +	tpm_crb_ffa->direct_msg_data.data2 = a0;
> +	tpm_crb_ffa->direct_msg_data.data3 = a1;
> +	tpm_crb_ffa->direct_msg_data.data4 = a2;
> +
> +	ret = msg_ops->sync_send_receive(tpm_crb_ffa->ffa_dev,
> +			&tpm_crb_ffa->direct_msg_data);
> +	if (!ret)
> +		ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data.data1);
> +
> +	return ret;
> +}
> +
> +/**
> + * tpm_crb_ffa_get_interface_version() - gets the ABI version of the TPM service
> + * @major: Pointer to caller-allocated buffer to hold the major version
> + *         number the ABI
> + * @minor: Pointer to caller-allocated buffer to hold the minor version
> + *         number the ABI
> + *
> + * Returns the major and minor version of the ABI of the FF-A based TPM.
> + * Allows the caller to evaluate its compatibility with the version of
> + * the ABI.
> + *
> + * Return: 0 on success, negative error code on failure.
> + */
> +int tpm_crb_ffa_get_interface_version(u16 *major, u16 *minor)
> +{
> +	int rc;
> +
> +	if (!tpm_crb_ffa)
> +		return -ENOENT;
> +
> +	if (IS_ERR_VALUE(tpm_crb_ffa))
> +		return -ENODEV;
> +
> +	if (!major || !minor)
> +		return -EINVAL;
> +
> +	guard(mutex)(&tpm_crb_ffa->msg_data_lock);
> +
> +	rc = __tpm_crb_ffa_send_recieve(CRB_FFA_GET_INTERFACE_VERSION, 0x00, 0x00, 0x00);
> +	if (!rc) {
> +		*major = CRB_FFA_MAJOR_VERSION(tpm_crb_ffa->direct_msg_data.data2);
> +		*minor = CRB_FFA_MINOR_VERSION(tpm_crb_ffa->direct_msg_data.data2);
> +	}
> +
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(tpm_crb_ffa_get_interface_version);
> +
> +/**
> + * tpm_crb_ffa_start() - signals the TPM that a field has changed in the CRB
> + * @request_type: Identifies whether the change to the CRB is in the command
> + *                fields or locality fields.
> + * @locality: Specifies the locality number.
> + *
> + * Used by the CRB driver
> + * that might be useful to those using or modifying it.  Begins with
> + * empty comment line, and may include additional embedded empty
> + * comment lines.
> + *
> + * Return: 0 on success, negative error code on failure.
> + */
> +int tpm_crb_ffa_start(int request_type, int locality)
> +{
> +	if (!tpm_crb_ffa)
> +		return -ENOENT;
> +
> +	if (IS_ERR_VALUE(tpm_crb_ffa))
> +		return -ENODEV;
> +
> +	guard(mutex)(&tpm_crb_ffa->msg_data_lock);
> +
> +	return __tpm_crb_ffa_send_recieve(CRB_FFA_START, request_type, locality, 0x00);
> +}
> +EXPORT_SYMBOL_GPL(tpm_crb_ffa_start);
> +
> +static int tpm_crb_ffa_probe(struct ffa_device *ffa_dev)
> +{
> +	struct tpm_crb_ffa *p;
> +	int rc;
> +
> +	/* only one instance of a TPM partition is supported */
> +	if (tpm_crb_ffa && !IS_ERR_VALUE(tpm_crb_ffa))
> +		return -EEXIST;
> +
> +	tpm_crb_ffa = ERR_PTR(-ENODEV); // set tpm_crb_ffa so we can detect probe failure
> +
> +	if (!ffa_partition_supports_direct_recv(ffa_dev)) {
> +		pr_err("TPM partition doesn't support direct message receive.\n");
> +		return -EINVAL;
> +	}
> +
> +	p = kzalloc(sizeof(*tpm_crb_ffa), GFP_KERNEL);
> +	if (!p)
> +		return -ENOMEM;
> +	tpm_crb_ffa = p;
> +
> +	mutex_init(&tpm_crb_ffa->msg_data_lock);
> +	tpm_crb_ffa->ffa_dev = ffa_dev;
> +	ffa_dev_set_drvdata(ffa_dev, tpm_crb_ffa);
> +
> +	/* if TPM is aarch32 use 32-bit SMCs */
> +	if (!ffa_partition_check_property(ffa_dev, FFA_PARTITION_AARCH64_EXEC))
> +		ffa_dev->ops->msg_ops->mode_32bit_set(ffa_dev);
> +
> +	/* verify compatibility of TPM service version number */
> +	rc = tpm_crb_ffa_get_interface_version(&tpm_crb_ffa->major_version,
> +					       &tpm_crb_ffa->minor_version);
> +	if (rc) {
> +		pr_err("failed to get crb interface version. rc:%d", rc);
> +		goto out;
> +	}
> +
> +	pr_info("ABI version %u.%u", tpm_crb_ffa->major_version,
> +		tpm_crb_ffa->minor_version);
> +
> +	if (tpm_crb_ffa->major_version != CRB_FFA_VERSION_MAJOR ||
> +	    (tpm_crb_ffa->minor_version > 0 &&
> +	    tpm_crb_ffa->minor_version < CRB_FFA_VERSION_MINOR)) {
> +		pr_err("Incompatible ABI version");
> +		goto out;
> +	}
> +
> +	return 0;
> +
> +out:
> +	kfree(tpm_crb_ffa);
> +	tpm_crb_ffa = ERR_PTR(-ENODEV);
> +	return -EINVAL;
> +}
> +
> +static void tpm_crb_ffa_remove(struct ffa_device *ffa_dev)
> +{
> +	kfree(tpm_crb_ffa);
> +	tpm_crb_ffa = NULL;
> +}
> +
> +static const struct ffa_device_id tpm_crb_ffa_device_id[] = {
> +	/* 17b862a4-1806-4faf-86b3-089a58353861 */
> +	{ UUID_INIT(0x17b862a4, 0x1806, 0x4faf,
> +		    0x86, 0xb3, 0x08, 0x9a, 0x58, 0x35, 0x38, 0x61) },
> +	{}
> +};
> +
> +static struct ffa_driver tpm_crb_ffa_driver = {
> +	.name = "ffa-crb",
> +	.probe = tpm_crb_ffa_probe,
> +	.remove = tpm_crb_ffa_remove,
> +	.id_table = tpm_crb_ffa_device_id,
> +};
> +
> +module_ffa_driver(tpm_crb_ffa_driver);
> +
> +MODULE_AUTHOR("Arm");
> +MODULE_DESCRIPTION("TPM CRB FFA driver");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/char/tpm/tpm_crb_ffa.h b/drivers/char/tpm/tpm_crb_ffa.h
> new file mode 100644
> index 000000000000..645c41ede10e
> --- /dev/null
> +++ b/drivers/char/tpm/tpm_crb_ffa.h
> @@ -0,0 +1,25 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2024 Arm Ltd.
> + *
> + * This device driver implements the TPM CRB start method
> + * as defined in the TPM Service Command Response Buffer
> + * Interface Over FF-A (DEN0138).
> + */
> +#ifndef _TPM_CRB_FFA_H
> +#define _TPM_CRB_FFA_H
> +
> +#if IS_REACHABLE(CONFIG_TCG_ARM_CRB_FFA)

Yes, this is correct given that it returns false on "vmlinux -> module"
situation ("vmlinux -> vmlinux" and "module -> module" still work).

> +int tpm_crb_ffa_init(void);
> +int tpm_crb_ffa_get_interface_version(u16 *major, u16 *minor);
> +int tpm_crb_ffa_start(int request_type, int locality);
> +#else
> +static inline int tpm_crb_ffa_init(void) { return 0; }
> +static inline int tpm_crb_ffa_get_interface_version(u16 *major, u16 *minor) { return 0; }
> +static inline int tpm_crb_ffa_start(int request_type, int locality) { return 0; }
> +#endif
> +
> +#define CRB_FFA_START_TYPE_COMMAND 0
> +#define CRB_FFA_START_TYPE_LOCALITY_REQUEST 1
> +
> +#endif
> -- 
> 2.34.1
> 
> 

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

[applying next week]

BR, Jarkko