Re: [PATCH v2 02/15] firmware: qcom: Add a generic PAS service

[Harshal Dev <harshal.dev@oss.qualcomm.com>]

On 3/12/2026 11:57 AM, Sumit Garg wrote:
> From: Sumit Garg <sumit.garg@oss.qualcomm.com>
> 
> Qcom platforms has the legacy of using non-standard SCM calls
> splintered over the various kernel drivers. These SCM calls aren't
> compliant with the standard SMC calling conventions which is a
> prerequisite to enable migration to the FF-A specifications from Arm.
> 
> OP-TEE as an alternative trusted OS to Qualcomm TEE (QTEE) can't
> support these non-standard SCM calls. And even for newer architectures
> with S-EL2 and Hafnium support, QTEE won't be able to support SCM
> calls either with FF-A requirements coming in. And with both OP-TEE
> and QTEE drivers well integrated in the TEE subsystem, it makes further
> sense to reuse the TEE bus client drivers infrastructure.
> 
> The added benefit of TEE bus infrastructure is that there is support
> for discoverable/enumerable services. With that client drivers don't
> have to manually invoke a special SCM call to know the service status.
> 
> So enable the generic Peripheral Authentication Service (PAS) provided
> by the firmware. It acts as the common layer with different TZ
> backends plugged in whether it's an SCM implementation or a proper
> TEE bus based PAS service implementation.
> 
> Signed-off-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
> ---
>  drivers/firmware/qcom/Kconfig          |   8 +
>  drivers/firmware/qcom/Makefile         |   1 +
>  drivers/firmware/qcom/qcom_pas.c       | 298 +++++++++++++++++++++++++
>  drivers/firmware/qcom/qcom_pas.h       |  53 +++++
>  include/linux/firmware/qcom/qcom_pas.h |  41 ++++
>  5 files changed, 401 insertions(+)
>  create mode 100644 drivers/firmware/qcom/qcom_pas.c
>  create mode 100644 drivers/firmware/qcom/qcom_pas.h
>  create mode 100644 include/linux/firmware/qcom/qcom_pas.h
> 
> diff --git a/drivers/firmware/qcom/Kconfig b/drivers/firmware/qcom/Kconfig
> index b477d54b495a..8653639d06db 100644
> --- a/drivers/firmware/qcom/Kconfig
> +++ b/drivers/firmware/qcom/Kconfig
> @@ -6,6 +6,14 @@
>  
>  menu "Qualcomm firmware drivers"
>  
> +config QCOM_PAS
> +	tristate
> +	help
> +	  Enable the generic Peripheral Authentication Service (PAS) provided
> +	  by the firmware. It acts as the common layer with different TZ
> +	  backends plugged in whether it's an SCM implementation or a proper
> +	  TEE bus based PAS service implementation.
> +
>  config QCOM_SCM
>  	select QCOM_TZMEM
>  	tristate
> diff --git a/drivers/firmware/qcom/Makefile b/drivers/firmware/qcom/Makefile
> index 0be40a1abc13..dc5ab45f906a 100644
> --- a/drivers/firmware/qcom/Makefile
> +++ b/drivers/firmware/qcom/Makefile
> @@ -8,3 +8,4 @@ qcom-scm-objs += qcom_scm.o qcom_scm-smc.o qcom_scm-legacy.o
>  obj-$(CONFIG_QCOM_TZMEM)	+= qcom_tzmem.o
>  obj-$(CONFIG_QCOM_QSEECOM)	+= qcom_qseecom.o
>  obj-$(CONFIG_QCOM_QSEECOM_UEFISECAPP) += qcom_qseecom_uefisecapp.o
> +obj-$(CONFIG_QCOM_PAS)		+= qcom_pas.o
> diff --git a/drivers/firmware/qcom/qcom_pas.c b/drivers/firmware/qcom/qcom_pas.c
> new file mode 100644
> index 000000000000..beb1bae55546
> --- /dev/null
> +++ b/drivers/firmware/qcom/qcom_pas.c
> @@ -0,0 +1,298 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> + */
> +
> +#include <linux/device/devres.h>
> +#include <linux/firmware/qcom/qcom_pas.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +
> +#include "qcom_pas.h"
> +
> +struct qcom_pas_ops *ops_ptr;
> +
> +/**
> + * devm_qcom_pas_context_alloc() - Allocate peripheral authentication service
> + *				   context for a given peripheral
> + *
> + * PAS context is device-resource managed, so the caller does not need
> + * to worry about freeing the context memory.
> + *
> + * @dev:	  PAS firmware device
> + * @pas_id:	  peripheral authentication service id
> + * @mem_phys:	  Subsystem reserve memory start address
> + * @mem_size:	  Subsystem reserve memory size
> + *
> + * Return: The new PAS context, or ERR_PTR() on failure.
> + */
> +struct qcom_pas_context *devm_qcom_pas_context_alloc(struct device *dev,
> +						     u32 pas_id,
> +						     phys_addr_t mem_phys,
> +						     size_t mem_size)
> +{
> +	struct qcom_pas_context *ctx;
> +
> +	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
> +	if (!ctx)
> +		return ERR_PTR(-ENOMEM);
> +
> +	ctx->dev = dev;
> +	ctx->pas_id = pas_id;
> +	ctx->mem_phys = mem_phys;
> +	ctx->mem_size = mem_size;
> +
> +	return ctx;
> +}
> +EXPORT_SYMBOL_GPL(devm_qcom_pas_context_alloc);
> +
> +/**
> + * qcom_pas_init_image() - Initialize peripheral authentication service state
> + *			   machine for a given peripheral, using the metadata
> + * @pas_id:	peripheral authentication service id
> + * @metadata:	pointer to memory containing ELF header, program header table
> + *		and optional blob of data used for authenticating the metadata
> + *		and the rest of the firmware
> + * @size:	size of the metadata
> + * @ctx:	optional pas context
> + *
> + * Return: 0 on success.
> + *
> + * Upon successful return, the PAS metadata context (@ctx) will be used to
> + * track the metadata allocation, this needs to be released by invoking
> + * qcom_pas_metadata_release() by the caller.
> + */
> +int qcom_pas_init_image(u32 pas_id, const void *metadata, size_t size,
> +			struct qcom_pas_context *ctx)
> +{

I think we should check for !ctx everywhere the way we are doing in qcom_pas_metadata_release().
!ctx->ptr may be checked conditionally based on whether the underlying implementation
uses it.

> +	if (ops_ptr)
> +		return ops_ptr->init_image(ops_ptr->dev, pas_id,
> +					   metadata, size, ctx);
> +
> +	return -ENODEV;
> +}
> +EXPORT_SYMBOL_GPL(qcom_pas_init_image);
> +
> +/**
> + * qcom_pas_metadata_release() - release metadata context
> + * @ctx:	pas context
> + */
> +void qcom_pas_metadata_release(struct qcom_pas_context *ctx)
> +{
> +	if (!ctx || !ctx->ptr)
> +		return;
> +
> +	if (ops_ptr)
> +		ops_ptr->metadata_release(ops_ptr->dev, ctx);
> +}
> +EXPORT_SYMBOL_GPL(qcom_pas_metadata_release);
> +
> +/**
> + * qcom_pas_mem_setup() - Prepare the memory related to a given peripheral
> + *			  for firmware loading
> + * @pas_id:	peripheral authentication service id
> + * @addr:	start address of memory area to prepare
> + * @size:	size of the memory area to prepare
> + *
> + * Return: 0 on success.
> + */
> +int qcom_pas_mem_setup(u32 pas_id, phys_addr_t addr, phys_addr_t size)
> +{
> +	if (ops_ptr)
> +		return ops_ptr->mem_setup(ops_ptr->dev, pas_id, addr, size);
> +
> +	return -ENODEV;
> +}
> +EXPORT_SYMBOL_GPL(qcom_pas_mem_setup);
> +
> +/**
> + * qcom_pas_get_rsc_table() - Retrieve the resource table in passed output buffer
> + *			      for a given peripheral.
> + *
> + * Qualcomm remote processor may rely on both static and dynamic resources for
> + * its functionality. Static resources typically refer to memory-mapped
> + * addresses required by the subsystem and are often embedded within the
> + * firmware binary and dynamic resources, such as shared memory in DDR etc.,
> + * are determined at runtime during the boot process.
> + *
> + * On Qualcomm Technologies devices, it's possible that static resources are
> + * not embedded in the firmware binary and instead are provided by TrustZone.
> + * However, dynamic resources are always expected to come from TrustZone. This
> + * indicates that for Qualcomm devices, all resources (static and dynamic) will
> + * be provided by TrustZone PAS service.
> + *
> + * If the remote processor firmware binary does contain static resources, they
> + * should be passed in input_rt. These will be forwarded to TrustZone for
> + * authentication. TrustZone will then append the dynamic resources and return
> + * the complete resource table in output_rt_tzm.
> + *
> + * If the remote processor firmware binary does not include a resource table,
> + * the caller of this function should set input_rt as NULL and input_rt_size
> + * as zero respectively.
> + *
> + * More about documentation on resource table data structures can be found in
> + * include/linux/remoteproc.h
> + *
> + * @ctx:	    PAS context
> + * @pas_id:	    peripheral authentication service id
> + * @input_rt:       resource table buffer which is present in firmware binary
> + * @input_rt_size:  size of the resource table present in firmware binary
> + * @output_rt_size: TrustZone expects caller should pass worst case size for
> + *		    the output_rt_tzm.
> + *
> + * Return:
> + *  On success, returns a pointer to the allocated buffer containing the final
> + *  resource table and output_rt_size will have actual resource table size from
> + *  TrustZone. The caller is responsible for freeing the buffer. On failure,
> + *  returns ERR_PTR(-errno).
> + */
> +struct resource_table *qcom_pas_get_rsc_table(struct qcom_pas_context *ctx,
> +					      void *input_rt,
> +					      size_t input_rt_size,
> +					      size_t *output_rt_size)
> +{

Check for !ctx here as well.

> +	if (ops_ptr)
> +		return ops_ptr->get_rsc_table(ops_ptr->dev, ctx, input_rt,
> +					      input_rt_size, output_rt_size);
> +
> +	return ERR_PTR(-ENODEV);
> +}
> +EXPORT_SYMBOL_GPL(qcom_pas_get_rsc_table);
> +
> +/**
> + * qcom_pas_auth_and_reset() - Authenticate the given peripheral firmware
> + *			       and reset the remote processor
> + * @pas_id:	peripheral authentication service id
> + *
> + * Return: 0 on success.
> + */
> +int qcom_pas_auth_and_reset(u32 pas_id)
> +{
> +	if (ops_ptr)
> +		return ops_ptr->auth_and_reset(ops_ptr->dev, pas_id);
> +
> +	return -ENODEV;
> +}
> +EXPORT_SYMBOL_GPL(qcom_pas_auth_and_reset);
> +
> +/**
> + * qcom_pas_prepare_and_auth_reset() - Prepare, authenticate, and reset the
> + *				       remote processor
> + *
> + * @ctx:	Context saved during call to qcom_scm_pas_context_init()
> + *
> + * This function performs the necessary steps to prepare a PAS subsystem,
> + * authenticate it using the provided metadata, and initiate a reset sequence.
> + *
> + * It should be used when Linux is in control setting up the IOMMU hardware
> + * for remote subsystem during secure firmware loading processes. The
> + * preparation step sets up a shmbridge over the firmware memory before
> + * TrustZone accesses the firmware memory region for authentication. The
> + * authentication step verifies the integrity and authenticity of the firmware
> + * or configuration using secure metadata. Finally, the reset step ensures the
> + * subsystem starts in a clean and sane state.
> + *
> + * Return: 0 on success, negative errno on failure.
> + */
> +int qcom_pas_prepare_and_auth_reset(struct qcom_pas_context *ctx)
> +{

Same here.

> +	if (ops_ptr)
> +		return ops_ptr->prepare_and_auth_reset(ops_ptr->dev, ctx);
> +
> +	return -ENODEV;
> +}
> +EXPORT_SYMBOL_GPL(qcom_pas_prepare_and_auth_reset);
> +
> +/**
> + * qcom_pas_set_remote_state() - Set the remote processor state
> + * @state:	peripheral state
> + * @pas_id:	peripheral authentication service id
> + *
> + * Return: 0 on success.
> + */
> +int qcom_pas_set_remote_state(u32 state, u32 pas_id)
> +{
> +	if (ops_ptr)
> +		return ops_ptr->set_remote_state(ops_ptr->dev, state, pas_id);
> +
> +	return -ENODEV;
> +}
> +EXPORT_SYMBOL_GPL(qcom_pas_set_remote_state);
> +
> +/**
> + * qcom_pas_shutdown() - Shut down the remote processor
> + * @pas_id:	peripheral authentication service id
> + *
> + * Return: 0 on success.
> + */
> +int qcom_pas_shutdown(u32 pas_id)
> +{
> +	if (ops_ptr)
> +		return ops_ptr->shutdown(ops_ptr->dev, pas_id);
> +
> +	return -ENODEV;
> +}
> +EXPORT_SYMBOL_GPL(qcom_pas_shutdown);
> +
> +/**
> + * qcom_pas_supported() - Check if the peripheral authentication service is
> + *			  available for the given peripheral
> + * @pas_id:	peripheral authentication service id
> + *
> + * Return: true if PAS is supported for this peripheral, otherwise false.
> + */
> +bool qcom_pas_supported(u32 pas_id)
> +{
> +	if (ops_ptr)
> +		return ops_ptr->supported(ops_ptr->dev, pas_id);
> +
> +	return false;
> +}
> +EXPORT_SYMBOL_GPL(qcom_pas_supported);
> +
> +/**
> + * qcom_pas_is_available() - Check for PAS service
> + *
> + * Return: true on success.
> + */
> +bool qcom_pas_is_available(void)
> +{
> +	/*
> +	 * The barrier for ops_ptr is intended to synchronize the data stores
> +	 * for the ops data structure when client drivers are in parallel
> +	 * checking for PAS service availability.
> +	 *
> +	 * Once the PAS backend becomes available, it is allowed for multiple
> +	 * threads to enter TZ for parallel bringup of co-processors during
> +	 * boot.
> +	 */
> +	return !!smp_load_acquire(&ops_ptr);
> +}
> +EXPORT_SYMBOL_GPL(qcom_pas_is_available);
> +
> +/**
> + * qcom_pas_ops_register() - Register PAS service ops
> + * @ops:	PAS service ops pointer
> + */
> +void qcom_pas_ops_register(struct qcom_pas_ops *ops)
> +{
> +	if (!qcom_pas_is_available())
> +		/* Paired with smp_load_acquire() in qcom_pas_is_available() */
> +		smp_store_release(&ops_ptr, ops);
> +	else
> +		pr_err("qcom_pas: ops already registered\n");
> +}
> +EXPORT_SYMBOL_GPL(qcom_pas_ops_register);
> +
> +/**
> + * qcom_pas_ops_unregister() - Unregister PAS service ops
> + */
> +void qcom_pas_ops_unregister(void)
> +{
> +	/* Paired with smp_load_acquire() in qcom_pas_is_available() */
> +	smp_store_release(&ops_ptr, NULL);
> +}
> +EXPORT_SYMBOL_GPL(qcom_pas_ops_unregister);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Qualcomm common TZ PAS driver");
> diff --git a/drivers/firmware/qcom/qcom_pas.h b/drivers/firmware/qcom/qcom_pas.h
> new file mode 100644
> index 000000000000..4ebed22178f8
> --- /dev/null
> +++ b/drivers/firmware/qcom/qcom_pas.h
> @@ -0,0 +1,53 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> + */
> +
> +#ifndef __QCOM_PAS_INT_H
> +#define __QCOM_PAS_INT_H
> +
> +struct device;
> +
> +/**
> + * struct qcom_pas_ops - Qcom Peripheral Authentication Service (PAS) ops
> + * @drv_name:			PAS driver name.
> + * @dev:			PAS device pointer.
> + * @supported:			Peripheral supported callback.
> + * @init_image:			Peripheral image initialization callback.
> + * @mem_setup:			Peripheral memory setup callback.
> + * @get_rsc_table:		Peripheral get resource table callback.
> + * @prepare_and_auth_reset:	Peripheral prepare firmware authentication and
> + *				reset callback.
> + * @auth_and_reset:		Peripheral firmware authentication and reset
> + *				callback.
> + * @set_remote_state:		Peripheral set remote state callback.
> + * @shutdown:			Peripheral shutdown callback.
> + * @metadata_release:		Image metadata release callback.
> + */
> +struct qcom_pas_ops {
> +	const char *drv_name;
> +	struct device *dev;
> +	bool (*supported)(struct device *dev, u32 pas_id);
> +	int (*init_image)(struct device *dev, u32 pas_id,
> +			  const void *metadata, size_t size,
> +			  struct qcom_pas_context *ctx);
> +	int (*mem_setup)(struct device *dev, u32 pas_id,
> +			 phys_addr_t addr, phys_addr_t size);
> +	void *(*get_rsc_table)(struct device *dev,
> +			       struct qcom_pas_context *ctx,
> +			       void *input_rt,
> +			       size_t input_rt_size,
> +			       size_t *output_rt_size);
> +	int (*prepare_and_auth_reset)(struct device *dev,
> +				      struct qcom_pas_context *ctx);
> +	int (*auth_and_reset)(struct device *dev, u32 pas_id);
> +	int (*set_remote_state)(struct device *dev, u32 state, u32 pas_id);
> +	int (*shutdown)(struct device *dev, u32 pas_id);
> +	void (*metadata_release)(struct device *dev,
> +				 struct qcom_pas_context *ctx);
> +};
> +
> +void qcom_pas_ops_register(struct qcom_pas_ops *ops);
> +void qcom_pas_ops_unregister(void);
> +
> +#endif /* __QCOM_PAS_INT_H */
> diff --git a/include/linux/firmware/qcom/qcom_pas.h b/include/linux/firmware/qcom/qcom_pas.h
> new file mode 100644
> index 000000000000..ef7328ecfa47
> --- /dev/null
> +++ b/include/linux/firmware/qcom/qcom_pas.h
> @@ -0,0 +1,41 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> + */
> +
> +#ifndef __QCOM_PAS_H
> +#define __QCOM_PAS_H
> +
> +#include <linux/err.h>
> +#include <linux/types.h>
> +
> +struct qcom_pas_context {
> +	struct device *dev;
> +	u32 pas_id;
> +	phys_addr_t mem_phys;
> +	size_t mem_size;
> +	void *ptr;
> +	dma_addr_t phys;
> +	ssize_t size;
> +	bool use_tzmem;
> +};
> +
> +bool qcom_pas_is_available(void);
> +struct qcom_pas_context *devm_qcom_pas_context_alloc(struct device *dev,
> +						     u32 pas_id,
> +						     phys_addr_t mem_phys,
> +						     size_t mem_size);
> +int qcom_pas_init_image(u32 pas_id, const void *metadata, size_t size,
> +			struct qcom_pas_context *ctx);
> +struct resource_table *qcom_pas_get_rsc_table(struct qcom_pas_context *ctx,
> +					      void *input_rt, size_t input_rt_size,
> +					      size_t *output_rt_size);
> +int qcom_pas_mem_setup(u32 pas_id, phys_addr_t addr, phys_addr_t size);
> +int qcom_pas_auth_and_reset(u32 pas_id);
> +int qcom_pas_prepare_and_auth_reset(struct qcom_pas_context *ctx);
> +int qcom_pas_set_remote_state(u32 state, u32 pas_id);
> +int qcom_pas_shutdown(u32 pas_id);
> +bool qcom_pas_supported(u32 pas_id);
> +void qcom_pas_metadata_release(struct qcom_pas_context *ctx);
> +
> +#endif /* __QCOM_PAS_H */

Regards,
Harshal