Re: [PATCH v4 02/15] firmware: qcom: Add a generic PAS service

Sumit Garg
2026-05-01T13:33:19Z

On Wed, Apr 29, 2026 at 02:41:19AM +0530, Mukesh Ojha wrote:
> On Mon, Apr 27, 2026 at 03:25:50PM +0530, 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
> > using S-EL2 with 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 | 288 +++++++++++++++++++++++++
> > drivers/firmware/qcom/qcom_pas.h | 50 +++++
> > include/linux/firmware/qcom/qcom_pas.h | 43 ++++
> > 5 files changed, 390 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..caf7fff33e5c
> > --- /dev/null
> > +++ b/drivers/firmware/qcom/qcom_pas.c
> > @@ -0,0 +1,288 @@
> > +// 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"
> > +
> > +static 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)
> > +{
> > + if (!ops_ptr)
> > + return -ENODEV;
> > +
> > + return ops_ptr->init_image(ops_ptr->dev, pas_id, metadata, size, ctx);
> > +}
> > +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 || !ops_ptr)
>
> reverse order..
>
> > + return;
> > +
> > + 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 -ENODEV;
> > +
> > + return ops_ptr->mem_setup(ops_ptr->dev, pas_id, addr, size);
> > +}
> > +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)
> > +{
> > + if (!ctx)
> > + return ERR_PTR(-EINVAL);
> > + if (!ops_ptr)
> > + return ERR_PTR(-ENODEV);
>
> same as below
>
> > +
> > + return ops_ptr->get_rsc_table(ops_ptr->dev, ctx, input_rt,
> > + input_rt_size, output_rt_size);
> > +}
> > +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 -ENODEV;
> > +
> > + return ops_ptr->auth_and_reset(ops_ptr->dev, pas_id);
> > +}
> > +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)
> > +{
> > + if (!ctx)
> > + return -EINVAL;
> > + if (!ops_ptr)
> > + return -ENODEV;
>
> They should be checked in reverse order, no point in checking ctx if
> ops_ptr is NULL .,

Ack.

>
> > +
> > + return ops_ptr->prepare_and_auth_reset(ops_ptr->dev, ctx);
> > +}
> > +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 -ENODEV;
> > +
> > + return ops_ptr->set_remote_state(ops_ptr->dev, state, pas_id);
> > +}
> > +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 -ENODEV;
> > +
> > + return ops_ptr->shutdown(ops_ptr->dev, pas_id);
> > +}
> > +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 false;
> > +
> > + return ops_ptr->supported(ops_ptr->dev, pas_id);
> > +}
> > +EXPORT_SYMBOL_GPL(qcom_pas_supported);
> > +
> > +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);
> > +
> > +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");
>
> pr_err("qcom_pas: ops already registered by %s\n", ops_ptr->drv_name);
>

Ack.

> > +}
> > +EXPORT_SYMBOL_GPL(qcom_pas_ops_register);
> > +
> > +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");
>
> generic ??

Naming is hard but your suggestion sounds more reasonable.

>
> > diff --git a/drivers/firmware/qcom/qcom_pas.h b/drivers/firmware/qcom/qcom_pas.h
> > new file mode 100644
> > index 000000000000..8643e2760602
> > --- /dev/null
> > +++ b/drivers/firmware/qcom/qcom_pas.h
> > @@ -0,0 +1,50 @@
> > +/* 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..65b1c9564458
> > --- /dev/null
> > +++ b/include/linux/firmware/qcom/qcom_pas.h
> > @@ -0,0 +1,43 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Copyright (c) 2010-2015, 2018-2019 The Linux Foundation. All rights reserved.
> > + * Copyright (C) 2015 Linaro Ltd.
> > + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> > + */
>
> Here, you kept the copyright but not in the C file.., from my view, both qcom_pas.c
> and qcom_pas.h are derivative work(>50%) and should carry the original license while
> drivers/firmware/qcom/qcom_pas.h is new work...

I think we discussed this in earlier iteration. The code in the C file
is mostly wrappers which are new but API comments are carried over. If
you insist then I will carry over the copyright.

>
> > +
> > +#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 */
> > --
> > 2.51.0
> >
>
> With above change,
>
> Reviewed-by: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>
>

Thanks.

-Sumit