diff mbox series

[v2,1/5] tpm_crb: implement driver compliant to CRB over FF-A

Message ID 20250212220548.400447-2-stuart.yoder@arm.com (mailing list archive)
State Superseded, archived
Headers show
Series Add support for the TPM FF-A start method | expand

Commit Message

Stuart Yoder Feb. 12, 2025, 10:05 p.m. UTC 
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.

Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
---
 drivers/char/tpm/Kconfig       |   9 +
 drivers/char/tpm/Makefile      |   1 +
 drivers/char/tpm/tpm_ffa_crb.c | 310 +++++++++++++++++++++++++++++++++
 drivers/char/tpm/tpm_ffa_crb.h |  30 ++++
 4 files changed, 350 insertions(+)
 create mode 100644 drivers/char/tpm/tpm_ffa_crb.c
 create mode 100644 drivers/char/tpm/tpm_ffa_crb.h

Comments

Jarkko Sakkinen Feb. 13, 2025, 10:14 p.m. UTC | #1 
On Wed, Feb 12, 2025 at 04:05:44PM -0600, 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.
> 
> Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
> ---
>  drivers/char/tpm/Kconfig       |   9 +
>  drivers/char/tpm/Makefile      |   1 +
>  drivers/char/tpm/tpm_ffa_crb.c | 310 +++++++++++++++++++++++++++++++++
>  drivers/char/tpm/tpm_ffa_crb.h |  30 ++++
>  4 files changed, 350 insertions(+)
>  create mode 100644 drivers/char/tpm/tpm_ffa_crb.c
>  create mode 100644 drivers/char/tpm/tpm_ffa_crb.h
> 
> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index 0fc9a510e059..af5ba7c63927 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_FFA_CRB
> +	tristate "TPM CRB over Arm FF-A Transport"
> +	depends on ARM_FFA_TRANSPORT
> +	default y if (TCG_CRB && ARM_FFA_TRANSPORT)
> +	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_ffa_crb.
> +
>  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..21f2eb5a485e 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-$(CONFIG_TCG_ARM_FFA_CRB) += tpm_ffa_crb.o
>  obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
>  obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
> diff --git a/drivers/char/tpm/tpm_ffa_crb.c b/drivers/char/tpm/tpm_ffa_crb.c
> new file mode 100644
> index 000000000000..56bd77864a47
> --- /dev/null
> +++ b/drivers/char/tpm/tpm_ffa_crb.c
> @@ -0,0 +1,310 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2024 Arm Ltd.
> + *
> + * Maintained by: <tpmdd-devel@lists.sourceforge.net>
> + *
> + * 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) "FFA_CRB: " fmt
> +
> +#include <linux/arm_ffa.h>
> +#include "tpm_ffa_crb.h"
> +
> +/* TPM service function status codes */
> +#define FFA_CRB_OK			0x05000001
> +#define FFA_CRB_OK_RESULTS_RETURNED	0x05000002
> +#define FFA_CRB_NOFUNC			0x8e000001
> +#define FFA_CRB_NOTSUP			0x8e000002
> +#define FFA_CRB_INVARG			0x8e000005
> +#define FFA_CRB_INV_CRB_CTRL_DATA	0x8e000006
> +#define FFA_CRB_ALREADY			0x8e000009
> +#define FFA_CRB_DENIED			0x8e00000a
> +#define FFA_CRB_NOMEM			0x8e00000b
> +
> +#define FFA_CRB_VERSION_MAJOR	1
> +#define FFA_CRB_VERSION_MINOR	0
> +
> +/* version encoding */
> +#define FFA_CRB_MAJOR_VERSION_MASK  GENMASK(30, 16)
> +#define FFA_CRB_MINOR_VERSION_MASK  GENMASK(15, 0)
> +#define FFA_CRB_MAJOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MAJOR_VERSION_MASK, (x))))
> +#define FFA_CRB_MINOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_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, FFA_CRB_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 FFA_CRB_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, FFA_CRB_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:
> + *     FFA_CRB_OK: the TPM service has been notified successfully
> + *     FFA_CRB_INVARG: one or more arguments are not valid
> + *     FFA_CRB_INV_CRB_CTRL_DATA: CRB control data or locality control
> + *         data at the given TPM locality is not valid
> + *     FFA_CRB_DENIED: the TPM has previously disabled locality requests and
> + *         command processing at the given locality
> + */
> +#define FFA_CRB_START 0x0f000201
> +
> +struct ffa_crb {
> +	struct ffa_device *ffa_dev;
> +	u16 major_version;
> +	u16 minor_version;
> +	struct mutex msg_data_lock;
> +	struct ffa_send_direct_data direct_msg_data;
> +};
> +
> +static struct ffa_crb *ffa_crb;
> +
> +static int ffa_crb_to_linux_errno(int errno)
> +{
> +	int rc;
> +
> +	switch (errno) {
> +	case FFA_CRB_OK:
> +		rc = 0;
> +		break;
> +	case FFA_CRB_OK_RESULTS_RETURNED:
> +		rc = 0;
> +		break;
> +	case FFA_CRB_NOFUNC:
> +		rc = -ENOENT;
> +		break;
> +	case FFA_CRB_NOTSUP:
> +		rc = -EPERM;
> +		break;
> +	case FFA_CRB_INVARG:
> +		rc = -EINVAL;
> +		break;
> +	case FFA_CRB_INV_CRB_CTRL_DATA:
> +		rc = -ENOEXEC;
> +		break;
> +	case FFA_CRB_ALREADY:
> +		rc = -EEXIST;
> +		break;
> +	case FFA_CRB_DENIED:
> +		rc = -EACCES;
> +		break;
> +	case FFA_CRB_NOMEM:
> +		rc = -ENOMEM;
> +		break;
> +	default:
> +		rc = -EINVAL;
> +	}
> +
> +	return rc;
> +}
> +
> +int ffa_crb_init(void)
> +{
> +	if (ffa_crb == NULL)
> +		return -ENOENT;
> +
> +	if (IS_ERR_VALUE(ffa_crb))
> +		return -ENODEV;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(ffa_crb_init);
> +
> +static int __ffa_crb_send_recieve(unsigned long func_id,
> +		unsigned long a0, unsigned long a1, unsigned long a2)
> +{
> +	int ret;
> +	const struct ffa_msg_ops *msg_ops;
> +
> +	if (ffa_crb == NULL)
> +		return -ENOENT;
> +
> +	msg_ops = ffa_crb->ffa_dev->ops->msg_ops;
> +
> +	memset(&ffa_crb->direct_msg_data, 0x00,
> +			sizeof(struct ffa_send_direct_data));
> +
> +	ffa_crb->direct_msg_data.data1 = func_id;
> +	ffa_crb->direct_msg_data.data2 = a0;
> +	ffa_crb->direct_msg_data.data3 = a1;
> +	ffa_crb->direct_msg_data.data4 = a2;
> +
> +	ret = msg_ops->sync_send_receive(ffa_crb->ffa_dev,
> +			&ffa_crb->direct_msg_data);
> +	if (!ret)
> +		ret = ffa_crb_to_linux_errno(ffa_crb->direct_msg_data.data1);
> +
> +	return ret;
> +}
> +
> +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor)
> +{
> +	int rc;
> +
> +	if (ffa_crb == NULL)
> +		return -ENOENT;
> +
> +	if (IS_ERR_VALUE(ffa_crb))
> +		return -ENODEV;
> +
> +	if (major == NULL || minor == NULL)
> +		return -EINVAL;
> +
> +	guard(mutex)(&ffa_crb->msg_data_lock);
> +
> +	rc = __ffa_crb_send_recieve(FFA_CRB_GET_INTERFACE_VERSION, 0x00, 0x00, 0x00);
> +	if (!rc) {
> +		*major = FFA_CRB_MAJOR_VERSION(ffa_crb->direct_msg_data.data2);
> +		*minor = FFA_CRB_MINOR_VERSION(ffa_crb->direct_msg_data.data2);
> +	}
> +
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(ffa_crb_get_interface_version);
> +
> +int ffa_crb_start(int request_type, int locality)
> +{
> +	if (ffa_crb == NULL)
> +		return -ENOENT;
> +
> +	if (IS_ERR_VALUE(ffa_crb))
> +		return -ENODEV;
> +
> +	guard(mutex)(&ffa_crb->msg_data_lock);
> +
> +	return __ffa_crb_send_recieve(FFA_CRB_START, request_type, locality, 0x00);
> +}
> +EXPORT_SYMBOL_GPL(ffa_crb_start);
> +
> +static int ffa_crb_probe(struct ffa_device *ffa_dev)
> +{
> +	int rc;
> +	struct ffa_crb *p;
> +
> +	/* only one instance of a TPM partition is supported */
> +	if (ffa_crb && !IS_ERR_VALUE(ffa_crb))
> +		return -EEXIST;
> +
> +	ffa_crb = ERR_PTR(-ENODEV); // set ffa_crb 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(*ffa_crb), GFP_KERNEL);
> +	if (!p)
> +		return -ENOMEM;
> +	ffa_crb = p;
> +
> +	mutex_init(&ffa_crb->msg_data_lock);
> +	ffa_crb->ffa_dev = ffa_dev;
> +	ffa_dev_set_drvdata(ffa_dev, ffa_crb);
> +
> +	/* 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 = ffa_crb_get_interface_version(&ffa_crb->major_version,
> +			&ffa_crb->minor_version);
> +	if (rc) {
> +		pr_err("failed to get crb interface version. rc:%d", rc);
> +		goto out;
> +	}
> +
> +	pr_info("ABI version %u.%u", ffa_crb->major_version,
> +		ffa_crb->minor_version);
> +
> +	if ((ffa_crb->major_version != FFA_CRB_VERSION_MAJOR) ||
> +	    (ffa_crb->minor_version < FFA_CRB_VERSION_MINOR)) {
> +		pr_err("Incompatible ABI version");
> +		goto out;
> +	}
> +
> +	return 0;
> +
> +out:
> +	kfree(ffa_crb);
> +	ffa_crb = ERR_PTR(-ENODEV);
> +	return -EINVAL;
> +}
> +
> +static void ffa_crb_remove(struct ffa_device *ffa_dev)
> +{
> +	kfree(ffa_crb);
> +	ffa_crb = NULL;
> +}
> +
> +static const struct ffa_device_id ffa_crb_device_id[] = {
> +	/* 17b862a4-1806-4faf-86b3-089a58353861 */
> +	{ UUID_INIT(0x17b862a4, 0x1806, 0x4faf,
> +		    0x86, 0xb3, 0x08, 0x9a, 0x58, 0x35, 0x38, 0x61) },
> +	{}
> +};
> +
> +static struct ffa_driver ffa_crb_driver = {
> +	.name = "ffa-crb",
> +	.probe = ffa_crb_probe,
> +	.remove = ffa_crb_remove,
> +	.id_table = ffa_crb_device_id,
> +};
> +
> +module_ffa_driver(ffa_crb_driver);
> +
> +MODULE_AUTHOR("Arm");
> +MODULE_DESCRIPTION("FFA CRB driver");
> +MODULE_VERSION("1.0");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/char/tpm/tpm_ffa_crb.h b/drivers/char/tpm/tpm_ffa_crb.h
> new file mode 100644
> index 000000000000..42327d285165
> --- /dev/null
> +++ b/drivers/char/tpm/tpm_ffa_crb.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2024 Arm Ltd.
> + *
> + * Authors:
> + * Stuart Yoder <stuart.yoder@arm.com>
> + *
> + * Maintained by: <tpmdd-devel@lists.sourceforge.net>
> + *
> + * This device driver implements the TPM CRB start method
> + * as defined in the TPM Service Command Response Buffer
> + * Interface Over FF-A (DEN0138).
> + */
> +#ifndef _FFA_CRB_H
> +#define _FFA_CRB_H
> +
> +#if IS_ENABLED(CONFIG_TCG_ARM_FFA_CRB)
> +int ffa_crb_init(void);
> +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor);
> +int ffa_crb_start(int request_type, int locality);
> +#else
> +static inline int ffa_crb_init(void) { return 0; }
> +static inline int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor) { return 0; }
> +static inline int ffa_crb_start(int request_type, int locality) { return 0; }
> +#endif
> +
> +#define FFA_CRB_START_TYPE_COMMAND 0
> +#define FFA_CRB_START_TYPE_LOCALITY_REQUEST 1
> +
> +#endif
> -- 
> 2.34.1
> 
> 

tpm_crb_ffa_*

BR, Jarkko
Stuart Yoder Feb. 13, 2025, 10:22 p.m. UTC | #2 
On 2/13/25 4:14 PM, Jarkko Sakkinen wrote:
> On Wed, Feb 12, 2025 at 04:05:44PM -0600, 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.
>>
>> Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
>> ---
>>   drivers/char/tpm/Kconfig       |   9 +
>>   drivers/char/tpm/Makefile      |   1 +
>>   drivers/char/tpm/tpm_ffa_crb.c | 310 +++++++++++++++++++++++++++++++++
>>   drivers/char/tpm/tpm_ffa_crb.h |  30 ++++
>>   4 files changed, 350 insertions(+)
>>   create mode 100644 drivers/char/tpm/tpm_ffa_crb.c
>>   create mode 100644 drivers/char/tpm/tpm_ffa_crb.h
>>
>> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
>> index 0fc9a510e059..af5ba7c63927 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_FFA_CRB
>> +	tristate "TPM CRB over Arm FF-A Transport"
>> +	depends on ARM_FFA_TRANSPORT
>> +	default y if (TCG_CRB && ARM_FFA_TRANSPORT)
>> +	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_ffa_crb.
>> +
>>   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..21f2eb5a485e 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-$(CONFIG_TCG_ARM_FFA_CRB) += tpm_ffa_crb.o
>>   obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
>>   obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
>> diff --git a/drivers/char/tpm/tpm_ffa_crb.c b/drivers/char/tpm/tpm_ffa_crb.c
>> new file mode 100644
>> index 000000000000..56bd77864a47
>> --- /dev/null
>> +++ b/drivers/char/tpm/tpm_ffa_crb.c
>> @@ -0,0 +1,310 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (C) 2024 Arm Ltd.
>> + *
>> + * Maintained by: <tpmdd-devel@lists.sourceforge.net>
>> + *
>> + * 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) "FFA_CRB: " fmt
>> +
>> +#include <linux/arm_ffa.h>
>> +#include "tpm_ffa_crb.h"
>> +
>> +/* TPM service function status codes */
>> +#define FFA_CRB_OK			0x05000001
>> +#define FFA_CRB_OK_RESULTS_RETURNED	0x05000002
>> +#define FFA_CRB_NOFUNC			0x8e000001
>> +#define FFA_CRB_NOTSUP			0x8e000002
>> +#define FFA_CRB_INVARG			0x8e000005
>> +#define FFA_CRB_INV_CRB_CTRL_DATA	0x8e000006
>> +#define FFA_CRB_ALREADY			0x8e000009
>> +#define FFA_CRB_DENIED			0x8e00000a
>> +#define FFA_CRB_NOMEM			0x8e00000b
>> +
>> +#define FFA_CRB_VERSION_MAJOR	1
>> +#define FFA_CRB_VERSION_MINOR	0
>> +
>> +/* version encoding */
>> +#define FFA_CRB_MAJOR_VERSION_MASK  GENMASK(30, 16)
>> +#define FFA_CRB_MINOR_VERSION_MASK  GENMASK(15, 0)
>> +#define FFA_CRB_MAJOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MAJOR_VERSION_MASK, (x))))
>> +#define FFA_CRB_MINOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_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, FFA_CRB_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 FFA_CRB_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, FFA_CRB_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:
>> + *     FFA_CRB_OK: the TPM service has been notified successfully
>> + *     FFA_CRB_INVARG: one or more arguments are not valid
>> + *     FFA_CRB_INV_CRB_CTRL_DATA: CRB control data or locality control
>> + *         data at the given TPM locality is not valid
>> + *     FFA_CRB_DENIED: the TPM has previously disabled locality requests and
>> + *         command processing at the given locality
>> + */
>> +#define FFA_CRB_START 0x0f000201
>> +
>> +struct ffa_crb {
>> +	struct ffa_device *ffa_dev;
>> +	u16 major_version;
>> +	u16 minor_version;
>> +	struct mutex msg_data_lock;
>> +	struct ffa_send_direct_data direct_msg_data;
>> +};
>> +
>> +static struct ffa_crb *ffa_crb;
>> +
>> +static int ffa_crb_to_linux_errno(int errno)
>> +{
>> +	int rc;
>> +
>> +	switch (errno) {
>> +	case FFA_CRB_OK:
>> +		rc = 0;
>> +		break;
>> +	case FFA_CRB_OK_RESULTS_RETURNED:
>> +		rc = 0;
>> +		break;
>> +	case FFA_CRB_NOFUNC:
>> +		rc = -ENOENT;
>> +		break;
>> +	case FFA_CRB_NOTSUP:
>> +		rc = -EPERM;
>> +		break;
>> +	case FFA_CRB_INVARG:
>> +		rc = -EINVAL;
>> +		break;
>> +	case FFA_CRB_INV_CRB_CTRL_DATA:
>> +		rc = -ENOEXEC;
>> +		break;
>> +	case FFA_CRB_ALREADY:
>> +		rc = -EEXIST;
>> +		break;
>> +	case FFA_CRB_DENIED:
>> +		rc = -EACCES;
>> +		break;
>> +	case FFA_CRB_NOMEM:
>> +		rc = -ENOMEM;
>> +		break;
>> +	default:
>> +		rc = -EINVAL;
>> +	}
>> +
>> +	return rc;
>> +}
>> +
>> +int ffa_crb_init(void)
>> +{
>> +	if (ffa_crb == NULL)
>> +		return -ENOENT;
>> +
>> +	if (IS_ERR_VALUE(ffa_crb))
>> +		return -ENODEV;
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(ffa_crb_init);
>> +
>> +static int __ffa_crb_send_recieve(unsigned long func_id,
>> +		unsigned long a0, unsigned long a1, unsigned long a2)
>> +{
>> +	int ret;
>> +	const struct ffa_msg_ops *msg_ops;
>> +
>> +	if (ffa_crb == NULL)
>> +		return -ENOENT;
>> +
>> +	msg_ops = ffa_crb->ffa_dev->ops->msg_ops;
>> +
>> +	memset(&ffa_crb->direct_msg_data, 0x00,
>> +			sizeof(struct ffa_send_direct_data));
>> +
>> +	ffa_crb->direct_msg_data.data1 = func_id;
>> +	ffa_crb->direct_msg_data.data2 = a0;
>> +	ffa_crb->direct_msg_data.data3 = a1;
>> +	ffa_crb->direct_msg_data.data4 = a2;
>> +
>> +	ret = msg_ops->sync_send_receive(ffa_crb->ffa_dev,
>> +			&ffa_crb->direct_msg_data);
>> +	if (!ret)
>> +		ret = ffa_crb_to_linux_errno(ffa_crb->direct_msg_data.data1);
>> +
>> +	return ret;
>> +}
>> +
>> +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor)
>> +{
>> +	int rc;
>> +
>> +	if (ffa_crb == NULL)
>> +		return -ENOENT;
>> +
>> +	if (IS_ERR_VALUE(ffa_crb))
>> +		return -ENODEV;
>> +
>> +	if (major == NULL || minor == NULL)
>> +		return -EINVAL;
>> +
>> +	guard(mutex)(&ffa_crb->msg_data_lock);
>> +
>> +	rc = __ffa_crb_send_recieve(FFA_CRB_GET_INTERFACE_VERSION, 0x00, 0x00, 0x00);
>> +	if (!rc) {
>> +		*major = FFA_CRB_MAJOR_VERSION(ffa_crb->direct_msg_data.data2);
>> +		*minor = FFA_CRB_MINOR_VERSION(ffa_crb->direct_msg_data.data2);
>> +	}
>> +
>> +	return rc;
>> +}
>> +EXPORT_SYMBOL_GPL(ffa_crb_get_interface_version);
>> +
>> +int ffa_crb_start(int request_type, int locality)
>> +{
>> +	if (ffa_crb == NULL)
>> +		return -ENOENT;
>> +
>> +	if (IS_ERR_VALUE(ffa_crb))
>> +		return -ENODEV;
>> +
>> +	guard(mutex)(&ffa_crb->msg_data_lock);
>> +
>> +	return __ffa_crb_send_recieve(FFA_CRB_START, request_type, locality, 0x00);
>> +}
>> +EXPORT_SYMBOL_GPL(ffa_crb_start);
>> +
>> +static int ffa_crb_probe(struct ffa_device *ffa_dev)
>> +{
>> +	int rc;
>> +	struct ffa_crb *p;
>> +
>> +	/* only one instance of a TPM partition is supported */
>> +	if (ffa_crb && !IS_ERR_VALUE(ffa_crb))
>> +		return -EEXIST;
>> +
>> +	ffa_crb = ERR_PTR(-ENODEV); // set ffa_crb 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(*ffa_crb), GFP_KERNEL);
>> +	if (!p)
>> +		return -ENOMEM;
>> +	ffa_crb = p;
>> +
>> +	mutex_init(&ffa_crb->msg_data_lock);
>> +	ffa_crb->ffa_dev = ffa_dev;
>> +	ffa_dev_set_drvdata(ffa_dev, ffa_crb);
>> +
>> +	/* 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 = ffa_crb_get_interface_version(&ffa_crb->major_version,
>> +			&ffa_crb->minor_version);
>> +	if (rc) {
>> +		pr_err("failed to get crb interface version. rc:%d", rc);
>> +		goto out;
>> +	}
>> +
>> +	pr_info("ABI version %u.%u", ffa_crb->major_version,
>> +		ffa_crb->minor_version);
>> +
>> +	if ((ffa_crb->major_version != FFA_CRB_VERSION_MAJOR) ||
>> +	    (ffa_crb->minor_version < FFA_CRB_VERSION_MINOR)) {
>> +		pr_err("Incompatible ABI version");
>> +		goto out;
>> +	}
>> +
>> +	return 0;
>> +
>> +out:
>> +	kfree(ffa_crb);
>> +	ffa_crb = ERR_PTR(-ENODEV);
>> +	return -EINVAL;
>> +}
>> +
>> +static void ffa_crb_remove(struct ffa_device *ffa_dev)
>> +{
>> +	kfree(ffa_crb);
>> +	ffa_crb = NULL;
>> +}
>> +
>> +static const struct ffa_device_id ffa_crb_device_id[] = {
>> +	/* 17b862a4-1806-4faf-86b3-089a58353861 */
>> +	{ UUID_INIT(0x17b862a4, 0x1806, 0x4faf,
>> +		    0x86, 0xb3, 0x08, 0x9a, 0x58, 0x35, 0x38, 0x61) },
>> +	{}
>> +};
>> +
>> +static struct ffa_driver ffa_crb_driver = {
>> +	.name = "ffa-crb",
>> +	.probe = ffa_crb_probe,
>> +	.remove = ffa_crb_remove,
>> +	.id_table = ffa_crb_device_id,
>> +};
>> +
>> +module_ffa_driver(ffa_crb_driver);
>> +
>> +MODULE_AUTHOR("Arm");
>> +MODULE_DESCRIPTION("FFA CRB driver");
>> +MODULE_VERSION("1.0");
>> +MODULE_LICENSE("GPL");
>> diff --git a/drivers/char/tpm/tpm_ffa_crb.h b/drivers/char/tpm/tpm_ffa_crb.h
>> new file mode 100644
>> index 000000000000..42327d285165
>> --- /dev/null
>> +++ b/drivers/char/tpm/tpm_ffa_crb.h
>> @@ -0,0 +1,30 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Copyright (C) 2024 Arm Ltd.
>> + *
>> + * Authors:
>> + * Stuart Yoder <stuart.yoder@arm.com>
>> + *
>> + * Maintained by: <tpmdd-devel@lists.sourceforge.net>
>> + *
>> + * This device driver implements the TPM CRB start method
>> + * as defined in the TPM Service Command Response Buffer
>> + * Interface Over FF-A (DEN0138).
>> + */
>> +#ifndef _FFA_CRB_H
>> +#define _FFA_CRB_H
>> +
>> +#if IS_ENABLED(CONFIG_TCG_ARM_FFA_CRB)
>> +int ffa_crb_init(void);
>> +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor);
>> +int ffa_crb_start(int request_type, int locality);
>> +#else
>> +static inline int ffa_crb_init(void) { return 0; }
>> +static inline int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor) { return 0; }
>> +static inline int ffa_crb_start(int request_type, int locality) { return 0; }
>> +#endif
>> +
>> +#define FFA_CRB_START_TYPE_COMMAND 0
>> +#define FFA_CRB_START_TYPE_LOCALITY_REQUEST 1
>> +
>> +#endif
>> -- 
>> 2.34.1
>>
>>
> 
> tpm_crb_ffa_*

I had renamed the source file to be tpm_ffa_crb.c based on your
previous feedback.  It would be good to be consistent.  Would
you prefer:

tpm_crb_ffa_*
or
tpm_ffa_crb_*

Thanks,
Stuart
Jarkko Sakkinen Feb. 13, 2025, 11:37 p.m. UTC | #3 
On Thu, Feb 13, 2025 at 04:22:44PM -0600, Stuart Yoder wrote:
> 
> 
> On 2/13/25 4:14 PM, Jarkko Sakkinen wrote:
> > On Wed, Feb 12, 2025 at 04:05:44PM -0600, 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.
> > > 
> > > Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
> > > ---
> > >   drivers/char/tpm/Kconfig       |   9 +
> > >   drivers/char/tpm/Makefile      |   1 +
> > >   drivers/char/tpm/tpm_ffa_crb.c | 310 +++++++++++++++++++++++++++++++++
> > >   drivers/char/tpm/tpm_ffa_crb.h |  30 ++++
> > >   4 files changed, 350 insertions(+)
> > >   create mode 100644 drivers/char/tpm/tpm_ffa_crb.c
> > >   create mode 100644 drivers/char/tpm/tpm_ffa_crb.h
> > > 
> > > diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> > > index 0fc9a510e059..af5ba7c63927 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_FFA_CRB
> > > +	tristate "TPM CRB over Arm FF-A Transport"
> > > +	depends on ARM_FFA_TRANSPORT
> > > +	default y if (TCG_CRB && ARM_FFA_TRANSPORT)
> > > +	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_ffa_crb.
> > > +
> > >   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..21f2eb5a485e 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-$(CONFIG_TCG_ARM_FFA_CRB) += tpm_ffa_crb.o
> > >   obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
> > >   obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
> > > diff --git a/drivers/char/tpm/tpm_ffa_crb.c b/drivers/char/tpm/tpm_ffa_crb.c
> > > new file mode 100644
> > > index 000000000000..56bd77864a47
> > > --- /dev/null
> > > +++ b/drivers/char/tpm/tpm_ffa_crb.c
> > > @@ -0,0 +1,310 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * Copyright (C) 2024 Arm Ltd.
> > > + *
> > > + * Maintained by: <tpmdd-devel@lists.sourceforge.net>
> > > + *
> > > + * 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) "FFA_CRB: " fmt
> > > +
> > > +#include <linux/arm_ffa.h>
> > > +#include "tpm_ffa_crb.h"
> > > +
> > > +/* TPM service function status codes */
> > > +#define FFA_CRB_OK			0x05000001
> > > +#define FFA_CRB_OK_RESULTS_RETURNED	0x05000002
> > > +#define FFA_CRB_NOFUNC			0x8e000001
> > > +#define FFA_CRB_NOTSUP			0x8e000002
> > > +#define FFA_CRB_INVARG			0x8e000005
> > > +#define FFA_CRB_INV_CRB_CTRL_DATA	0x8e000006
> > > +#define FFA_CRB_ALREADY			0x8e000009
> > > +#define FFA_CRB_DENIED			0x8e00000a
> > > +#define FFA_CRB_NOMEM			0x8e00000b
> > > +
> > > +#define FFA_CRB_VERSION_MAJOR	1
> > > +#define FFA_CRB_VERSION_MINOR	0
> > > +
> > > +/* version encoding */
> > > +#define FFA_CRB_MAJOR_VERSION_MASK  GENMASK(30, 16)
> > > +#define FFA_CRB_MINOR_VERSION_MASK  GENMASK(15, 0)
> > > +#define FFA_CRB_MAJOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MAJOR_VERSION_MASK, (x))))
> > > +#define FFA_CRB_MINOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_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, FFA_CRB_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 FFA_CRB_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, FFA_CRB_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:
> > > + *     FFA_CRB_OK: the TPM service has been notified successfully
> > > + *     FFA_CRB_INVARG: one or more arguments are not valid
> > > + *     FFA_CRB_INV_CRB_CTRL_DATA: CRB control data or locality control
> > > + *         data at the given TPM locality is not valid
> > > + *     FFA_CRB_DENIED: the TPM has previously disabled locality requests and
> > > + *         command processing at the given locality
> > > + */
> > > +#define FFA_CRB_START 0x0f000201
> > > +
> > > +struct ffa_crb {
> > > +	struct ffa_device *ffa_dev;
> > > +	u16 major_version;
> > > +	u16 minor_version;
> > > +	struct mutex msg_data_lock;
> > > +	struct ffa_send_direct_data direct_msg_data;
> > > +};
> > > +
> > > +static struct ffa_crb *ffa_crb;
> > > +
> > > +static int ffa_crb_to_linux_errno(int errno)
> > > +{
> > > +	int rc;
> > > +
> > > +	switch (errno) {
> > > +	case FFA_CRB_OK:
> > > +		rc = 0;
> > > +		break;
> > > +	case FFA_CRB_OK_RESULTS_RETURNED:
> > > +		rc = 0;
> > > +		break;
> > > +	case FFA_CRB_NOFUNC:
> > > +		rc = -ENOENT;
> > > +		break;
> > > +	case FFA_CRB_NOTSUP:
> > > +		rc = -EPERM;
> > > +		break;
> > > +	case FFA_CRB_INVARG:
> > > +		rc = -EINVAL;
> > > +		break;
> > > +	case FFA_CRB_INV_CRB_CTRL_DATA:
> > > +		rc = -ENOEXEC;
> > > +		break;
> > > +	case FFA_CRB_ALREADY:
> > > +		rc = -EEXIST;
> > > +		break;
> > > +	case FFA_CRB_DENIED:
> > > +		rc = -EACCES;
> > > +		break;
> > > +	case FFA_CRB_NOMEM:
> > > +		rc = -ENOMEM;
> > > +		break;
> > > +	default:
> > > +		rc = -EINVAL;
> > > +	}
> > > +
> > > +	return rc;
> > > +}
> > > +
> > > +int ffa_crb_init(void)
> > > +{
> > > +	if (ffa_crb == NULL)
> > > +		return -ENOENT;
> > > +
> > > +	if (IS_ERR_VALUE(ffa_crb))
> > > +		return -ENODEV;
> > > +
> > > +	return 0;
> > > +}
> > > +EXPORT_SYMBOL_GPL(ffa_crb_init);
> > > +
> > > +static int __ffa_crb_send_recieve(unsigned long func_id,
> > > +		unsigned long a0, unsigned long a1, unsigned long a2)
> > > +{
> > > +	int ret;
> > > +	const struct ffa_msg_ops *msg_ops;
> > > +
> > > +	if (ffa_crb == NULL)
> > > +		return -ENOENT;
> > > +
> > > +	msg_ops = ffa_crb->ffa_dev->ops->msg_ops;
> > > +
> > > +	memset(&ffa_crb->direct_msg_data, 0x00,
> > > +			sizeof(struct ffa_send_direct_data));
> > > +
> > > +	ffa_crb->direct_msg_data.data1 = func_id;
> > > +	ffa_crb->direct_msg_data.data2 = a0;
> > > +	ffa_crb->direct_msg_data.data3 = a1;
> > > +	ffa_crb->direct_msg_data.data4 = a2;
> > > +
> > > +	ret = msg_ops->sync_send_receive(ffa_crb->ffa_dev,
> > > +			&ffa_crb->direct_msg_data);
> > > +	if (!ret)
> > > +		ret = ffa_crb_to_linux_errno(ffa_crb->direct_msg_data.data1);
> > > +
> > > +	return ret;
> > > +}
> > > +
> > > +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor)
> > > +{
> > > +	int rc;
> > > +
> > > +	if (ffa_crb == NULL)
> > > +		return -ENOENT;
> > > +
> > > +	if (IS_ERR_VALUE(ffa_crb))
> > > +		return -ENODEV;
> > > +
> > > +	if (major == NULL || minor == NULL)
> > > +		return -EINVAL;
> > > +
> > > +	guard(mutex)(&ffa_crb->msg_data_lock);
> > > +
> > > +	rc = __ffa_crb_send_recieve(FFA_CRB_GET_INTERFACE_VERSION, 0x00, 0x00, 0x00);
> > > +	if (!rc) {
> > > +		*major = FFA_CRB_MAJOR_VERSION(ffa_crb->direct_msg_data.data2);
> > > +		*minor = FFA_CRB_MINOR_VERSION(ffa_crb->direct_msg_data.data2);
> > > +	}
> > > +
> > > +	return rc;
> > > +}
> > > +EXPORT_SYMBOL_GPL(ffa_crb_get_interface_version);
> > > +
> > > +int ffa_crb_start(int request_type, int locality)
> > > +{
> > > +	if (ffa_crb == NULL)
> > > +		return -ENOENT;
> > > +
> > > +	if (IS_ERR_VALUE(ffa_crb))
> > > +		return -ENODEV;
> > > +
> > > +	guard(mutex)(&ffa_crb->msg_data_lock);
> > > +
> > > +	return __ffa_crb_send_recieve(FFA_CRB_START, request_type, locality, 0x00);
> > > +}
> > > +EXPORT_SYMBOL_GPL(ffa_crb_start);
> > > +
> > > +static int ffa_crb_probe(struct ffa_device *ffa_dev)
> > > +{
> > > +	int rc;
> > > +	struct ffa_crb *p;
> > > +
> > > +	/* only one instance of a TPM partition is supported */
> > > +	if (ffa_crb && !IS_ERR_VALUE(ffa_crb))
> > > +		return -EEXIST;
> > > +
> > > +	ffa_crb = ERR_PTR(-ENODEV); // set ffa_crb 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(*ffa_crb), GFP_KERNEL);
> > > +	if (!p)
> > > +		return -ENOMEM;
> > > +	ffa_crb = p;
> > > +
> > > +	mutex_init(&ffa_crb->msg_data_lock);
> > > +	ffa_crb->ffa_dev = ffa_dev;
> > > +	ffa_dev_set_drvdata(ffa_dev, ffa_crb);
> > > +
> > > +	/* 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 = ffa_crb_get_interface_version(&ffa_crb->major_version,
> > > +			&ffa_crb->minor_version);
> > > +	if (rc) {
> > > +		pr_err("failed to get crb interface version. rc:%d", rc);
> > > +		goto out;
> > > +	}
> > > +
> > > +	pr_info("ABI version %u.%u", ffa_crb->major_version,
> > > +		ffa_crb->minor_version);
> > > +
> > > +	if ((ffa_crb->major_version != FFA_CRB_VERSION_MAJOR) ||
> > > +	    (ffa_crb->minor_version < FFA_CRB_VERSION_MINOR)) {
> > > +		pr_err("Incompatible ABI version");
> > > +		goto out;
> > > +	}
> > > +
> > > +	return 0;
> > > +
> > > +out:
> > > +	kfree(ffa_crb);
> > > +	ffa_crb = ERR_PTR(-ENODEV);
> > > +	return -EINVAL;
> > > +}
> > > +
> > > +static void ffa_crb_remove(struct ffa_device *ffa_dev)
> > > +{
> > > +	kfree(ffa_crb);
> > > +	ffa_crb = NULL;
> > > +}
> > > +
> > > +static const struct ffa_device_id ffa_crb_device_id[] = {
> > > +	/* 17b862a4-1806-4faf-86b3-089a58353861 */
> > > +	{ UUID_INIT(0x17b862a4, 0x1806, 0x4faf,
> > > +		    0x86, 0xb3, 0x08, 0x9a, 0x58, 0x35, 0x38, 0x61) },
> > > +	{}
> > > +};
> > > +
> > > +static struct ffa_driver ffa_crb_driver = {
> > > +	.name = "ffa-crb",
> > > +	.probe = ffa_crb_probe,
> > > +	.remove = ffa_crb_remove,
> > > +	.id_table = ffa_crb_device_id,
> > > +};
> > > +
> > > +module_ffa_driver(ffa_crb_driver);
> > > +
> > > +MODULE_AUTHOR("Arm");
> > > +MODULE_DESCRIPTION("FFA CRB driver");
> > > +MODULE_VERSION("1.0");
> > > +MODULE_LICENSE("GPL");
> > > diff --git a/drivers/char/tpm/tpm_ffa_crb.h b/drivers/char/tpm/tpm_ffa_crb.h
> > > new file mode 100644
> > > index 000000000000..42327d285165
> > > --- /dev/null
> > > +++ b/drivers/char/tpm/tpm_ffa_crb.h
> > > @@ -0,0 +1,30 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-only */
> > > +/*
> > > + * Copyright (C) 2024 Arm Ltd.
> > > + *
> > > + * Authors:
> > > + * Stuart Yoder <stuart.yoder@arm.com>
> > > + *
> > > + * Maintained by: <tpmdd-devel@lists.sourceforge.net>
> > > + *
> > > + * This device driver implements the TPM CRB start method
> > > + * as defined in the TPM Service Command Response Buffer
> > > + * Interface Over FF-A (DEN0138).
> > > + */
> > > +#ifndef _FFA_CRB_H
> > > +#define _FFA_CRB_H
> > > +
> > > +#if IS_ENABLED(CONFIG_TCG_ARM_FFA_CRB)
> > > +int ffa_crb_init(void);
> > > +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor);
> > > +int ffa_crb_start(int request_type, int locality);
> > > +#else
> > > +static inline int ffa_crb_init(void) { return 0; }
> > > +static inline int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor) { return 0; }
> > > +static inline int ffa_crb_start(int request_type, int locality) { return 0; }
> > > +#endif
> > > +
> > > +#define FFA_CRB_START_TYPE_COMMAND 0
> > > +#define FFA_CRB_START_TYPE_LOCALITY_REQUEST 1
> > > +
> > > +#endif
> > > -- 
> > > 2.34.1
> > > 
> > > 
> > 
> > tpm_crb_ffa_*
> 
> I had renamed the source file to be tpm_ffa_crb.c based on your
> previous feedback.  It would be good to be consistent.  Would
> you prefer:
> 
> tpm_crb_ffa_*
> or
> tpm_ffa_crb_*

I made a mistake and apologize for that!

I thought about tpm_crb_ffa_* but wrote in misorder.

Sorry about this!

BR, Jarkko
kernel test robot Feb. 16, 2025, 12:28 a.m. UTC | #4 
Hi Stuart,

kernel test robot noticed the following build warnings:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus rafael-pm/linux-next rafael-pm/bleeding-edge linus/master v6.14-rc2 next-20250214]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Stuart-Yoder/tpm_crb-implement-driver-compliant-to-CRB-over-FF-A/20250213-060938
base:   char-misc/char-misc-testing
patch link:    https://lore.kernel.org/r/20250212220548.400447-2-stuart.yoder%40arm.com
patch subject: [PATCH v2 1/5] tpm_crb: implement driver compliant to CRB over FF-A
config: arm64-randconfig-r073-20250214 (https://download.01.org/0day-ci/archive/20250216/202502160801.zzYlGtHn-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502160801.zzYlGtHn-lkp@intel.com/

smatch warnings:
drivers/char/tpm/tpm_ffa_crb.c:272 ffa_crb_probe() warn: unsigned 'ffa_crb->minor_version' is never less than zero.

vim +272 drivers/char/tpm/tpm_ffa_crb.c

   230	
   231	static int ffa_crb_probe(struct ffa_device *ffa_dev)
   232	{
   233		int rc;
   234		struct ffa_crb *p;
   235	
   236		/* only one instance of a TPM partition is supported */
   237		if (ffa_crb && !IS_ERR_VALUE(ffa_crb))
   238			return -EEXIST;
   239	
   240		ffa_crb = ERR_PTR(-ENODEV); // set ffa_crb so we can detect probe failure
   241	
   242		if (!ffa_partition_supports_direct_recv(ffa_dev)) {
   243			pr_err("TPM partition doesn't support direct message receive.\n");
   244			return -EINVAL;
   245		}
   246	
   247		p = kzalloc(sizeof(*ffa_crb), GFP_KERNEL);
   248		if (!p)
   249			return -ENOMEM;
   250		ffa_crb = p;
   251	
   252		mutex_init(&ffa_crb->msg_data_lock);
   253		ffa_crb->ffa_dev = ffa_dev;
   254		ffa_dev_set_drvdata(ffa_dev, ffa_crb);
   255	
   256		/* if TPM is aarch32 use 32-bit SMCs */
   257		if (!ffa_partition_check_property(ffa_dev, FFA_PARTITION_AARCH64_EXEC))
   258			ffa_dev->ops->msg_ops->mode_32bit_set(ffa_dev);
   259	
   260		/* verify compatibility of TPM service version number */
   261		rc = ffa_crb_get_interface_version(&ffa_crb->major_version,
   262				&ffa_crb->minor_version);
   263		if (rc) {
   264			pr_err("failed to get crb interface version. rc:%d", rc);
   265			goto out;
   266		}
   267	
   268		pr_info("ABI version %u.%u", ffa_crb->major_version,
   269			ffa_crb->minor_version);
   270	
   271		if ((ffa_crb->major_version != FFA_CRB_VERSION_MAJOR) ||
 > 272		    (ffa_crb->minor_version < FFA_CRB_VERSION_MINOR)) {
   273			pr_err("Incompatible ABI version");
   274			goto out;
   275		}
   276	
   277		return 0;
   278	
   279	out:
   280		kfree(ffa_crb);
   281		ffa_crb = ERR_PTR(-ENODEV);
   282		return -EINVAL;
   283	}
   284
diff mbox series

Patch

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index 0fc9a510e059..af5ba7c63927 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_FFA_CRB
+	tristate "TPM CRB over Arm FF-A Transport"
+	depends on ARM_FFA_TRANSPORT
+	default y if (TCG_CRB && ARM_FFA_TRANSPORT)
+	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_ffa_crb.
+
 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..21f2eb5a485e 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-$(CONFIG_TCG_ARM_FFA_CRB) += tpm_ffa_crb.o
 obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
 obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
diff --git a/drivers/char/tpm/tpm_ffa_crb.c b/drivers/char/tpm/tpm_ffa_crb.c
new file mode 100644
index 000000000000..56bd77864a47
--- /dev/null
+++ b/drivers/char/tpm/tpm_ffa_crb.c
@@ -0,0 +1,310 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Arm Ltd.
+ *
+ * Maintained by: <tpmdd-devel@lists.sourceforge.net>
+ *
+ * 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) "FFA_CRB: " fmt
+
+#include <linux/arm_ffa.h>
+#include "tpm_ffa_crb.h"
+
+/* TPM service function status codes */
+#define FFA_CRB_OK			0x05000001
+#define FFA_CRB_OK_RESULTS_RETURNED	0x05000002
+#define FFA_CRB_NOFUNC			0x8e000001
+#define FFA_CRB_NOTSUP			0x8e000002
+#define FFA_CRB_INVARG			0x8e000005
+#define FFA_CRB_INV_CRB_CTRL_DATA	0x8e000006
+#define FFA_CRB_ALREADY			0x8e000009
+#define FFA_CRB_DENIED			0x8e00000a
+#define FFA_CRB_NOMEM			0x8e00000b
+
+#define FFA_CRB_VERSION_MAJOR	1
+#define FFA_CRB_VERSION_MINOR	0
+
+/* version encoding */
+#define FFA_CRB_MAJOR_VERSION_MASK  GENMASK(30, 16)
+#define FFA_CRB_MINOR_VERSION_MASK  GENMASK(15, 0)
+#define FFA_CRB_MAJOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MAJOR_VERSION_MASK, (x))))
+#define FFA_CRB_MINOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_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, FFA_CRB_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 FFA_CRB_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, FFA_CRB_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:
+ *     FFA_CRB_OK: the TPM service has been notified successfully
+ *     FFA_CRB_INVARG: one or more arguments are not valid
+ *     FFA_CRB_INV_CRB_CTRL_DATA: CRB control data or locality control
+ *         data at the given TPM locality is not valid
+ *     FFA_CRB_DENIED: the TPM has previously disabled locality requests and
+ *         command processing at the given locality
+ */
+#define FFA_CRB_START 0x0f000201
+
+struct ffa_crb {
+	struct ffa_device *ffa_dev;
+	u16 major_version;
+	u16 minor_version;
+	struct mutex msg_data_lock;
+	struct ffa_send_direct_data direct_msg_data;
+};
+
+static struct ffa_crb *ffa_crb;
+
+static int ffa_crb_to_linux_errno(int errno)
+{
+	int rc;
+
+	switch (errno) {
+	case FFA_CRB_OK:
+		rc = 0;
+		break;
+	case FFA_CRB_OK_RESULTS_RETURNED:
+		rc = 0;
+		break;
+	case FFA_CRB_NOFUNC:
+		rc = -ENOENT;
+		break;
+	case FFA_CRB_NOTSUP:
+		rc = -EPERM;
+		break;
+	case FFA_CRB_INVARG:
+		rc = -EINVAL;
+		break;
+	case FFA_CRB_INV_CRB_CTRL_DATA:
+		rc = -ENOEXEC;
+		break;
+	case FFA_CRB_ALREADY:
+		rc = -EEXIST;
+		break;
+	case FFA_CRB_DENIED:
+		rc = -EACCES;
+		break;
+	case FFA_CRB_NOMEM:
+		rc = -ENOMEM;
+		break;
+	default:
+		rc = -EINVAL;
+	}
+
+	return rc;
+}
+
+int ffa_crb_init(void)
+{
+	if (ffa_crb == NULL)
+		return -ENOENT;
+
+	if (IS_ERR_VALUE(ffa_crb))
+		return -ENODEV;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ffa_crb_init);
+
+static int __ffa_crb_send_recieve(unsigned long func_id,
+		unsigned long a0, unsigned long a1, unsigned long a2)
+{
+	int ret;
+	const struct ffa_msg_ops *msg_ops;
+
+	if (ffa_crb == NULL)
+		return -ENOENT;
+
+	msg_ops = ffa_crb->ffa_dev->ops->msg_ops;
+
+	memset(&ffa_crb->direct_msg_data, 0x00,
+			sizeof(struct ffa_send_direct_data));
+
+	ffa_crb->direct_msg_data.data1 = func_id;
+	ffa_crb->direct_msg_data.data2 = a0;
+	ffa_crb->direct_msg_data.data3 = a1;
+	ffa_crb->direct_msg_data.data4 = a2;
+
+	ret = msg_ops->sync_send_receive(ffa_crb->ffa_dev,
+			&ffa_crb->direct_msg_data);
+	if (!ret)
+		ret = ffa_crb_to_linux_errno(ffa_crb->direct_msg_data.data1);
+
+	return ret;
+}
+
+int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor)
+{
+	int rc;
+
+	if (ffa_crb == NULL)
+		return -ENOENT;
+
+	if (IS_ERR_VALUE(ffa_crb))
+		return -ENODEV;
+
+	if (major == NULL || minor == NULL)
+		return -EINVAL;
+
+	guard(mutex)(&ffa_crb->msg_data_lock);
+
+	rc = __ffa_crb_send_recieve(FFA_CRB_GET_INTERFACE_VERSION, 0x00, 0x00, 0x00);
+	if (!rc) {
+		*major = FFA_CRB_MAJOR_VERSION(ffa_crb->direct_msg_data.data2);
+		*minor = FFA_CRB_MINOR_VERSION(ffa_crb->direct_msg_data.data2);
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(ffa_crb_get_interface_version);
+
+int ffa_crb_start(int request_type, int locality)
+{
+	if (ffa_crb == NULL)
+		return -ENOENT;
+
+	if (IS_ERR_VALUE(ffa_crb))
+		return -ENODEV;
+
+	guard(mutex)(&ffa_crb->msg_data_lock);
+
+	return __ffa_crb_send_recieve(FFA_CRB_START, request_type, locality, 0x00);
+}
+EXPORT_SYMBOL_GPL(ffa_crb_start);
+
+static int ffa_crb_probe(struct ffa_device *ffa_dev)
+{
+	int rc;
+	struct ffa_crb *p;
+
+	/* only one instance of a TPM partition is supported */
+	if (ffa_crb && !IS_ERR_VALUE(ffa_crb))
+		return -EEXIST;
+
+	ffa_crb = ERR_PTR(-ENODEV); // set ffa_crb 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(*ffa_crb), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+	ffa_crb = p;
+
+	mutex_init(&ffa_crb->msg_data_lock);
+	ffa_crb->ffa_dev = ffa_dev;
+	ffa_dev_set_drvdata(ffa_dev, ffa_crb);
+
+	/* 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 = ffa_crb_get_interface_version(&ffa_crb->major_version,
+			&ffa_crb->minor_version);
+	if (rc) {
+		pr_err("failed to get crb interface version. rc:%d", rc);
+		goto out;
+	}
+
+	pr_info("ABI version %u.%u", ffa_crb->major_version,
+		ffa_crb->minor_version);
+
+	if ((ffa_crb->major_version != FFA_CRB_VERSION_MAJOR) ||
+	    (ffa_crb->minor_version < FFA_CRB_VERSION_MINOR)) {
+		pr_err("Incompatible ABI version");
+		goto out;
+	}
+
+	return 0;
+
+out:
+	kfree(ffa_crb);
+	ffa_crb = ERR_PTR(-ENODEV);
+	return -EINVAL;
+}
+
+static void ffa_crb_remove(struct ffa_device *ffa_dev)
+{
+	kfree(ffa_crb);
+	ffa_crb = NULL;
+}
+
+static const struct ffa_device_id ffa_crb_device_id[] = {
+	/* 17b862a4-1806-4faf-86b3-089a58353861 */
+	{ UUID_INIT(0x17b862a4, 0x1806, 0x4faf,
+		    0x86, 0xb3, 0x08, 0x9a, 0x58, 0x35, 0x38, 0x61) },
+	{}
+};
+
+static struct ffa_driver ffa_crb_driver = {
+	.name = "ffa-crb",
+	.probe = ffa_crb_probe,
+	.remove = ffa_crb_remove,
+	.id_table = ffa_crb_device_id,
+};
+
+module_ffa_driver(ffa_crb_driver);
+
+MODULE_AUTHOR("Arm");
+MODULE_DESCRIPTION("FFA CRB driver");
+MODULE_VERSION("1.0");
+MODULE_LICENSE("GPL");
diff --git a/drivers/char/tpm/tpm_ffa_crb.h b/drivers/char/tpm/tpm_ffa_crb.h
new file mode 100644
index 000000000000..42327d285165
--- /dev/null
+++ b/drivers/char/tpm/tpm_ffa_crb.h
@@ -0,0 +1,30 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2024 Arm Ltd.
+ *
+ * Authors:
+ * Stuart Yoder <stuart.yoder@arm.com>
+ *
+ * Maintained by: <tpmdd-devel@lists.sourceforge.net>
+ *
+ * This device driver implements the TPM CRB start method
+ * as defined in the TPM Service Command Response Buffer
+ * Interface Over FF-A (DEN0138).
+ */
+#ifndef _FFA_CRB_H
+#define _FFA_CRB_H
+
+#if IS_ENABLED(CONFIG_TCG_ARM_FFA_CRB)
+int ffa_crb_init(void);
+int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor);
+int ffa_crb_start(int request_type, int locality);
+#else
+static inline int ffa_crb_init(void) { return 0; }
+static inline int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor) { return 0; }
+static inline int ffa_crb_start(int request_type, int locality) { return 0; }
+#endif
+
+#define FFA_CRB_START_TYPE_COMMAND 0
+#define FFA_CRB_START_TYPE_LOCALITY_REQUEST 1
+
+#endif