On Thu, Nov 13, 2025 at 04:05:54PM +0530, Mukesh Ojha wrote:
> When the Peripheral Authentication Service (PAS) method runs on a SoC
> where Linux operates at EL2 (i.e., without the Gunyah hypervisor), the
> reset sequences are handled by TrustZone. In such cases, Linux must
> perform additional steps before invoking PAS SMC calls, such as creating
> a SHM bridge. Therefore, PAS SMC calls require awareness and handling of
> these additional steps when Linux runs at EL2.
>
> To support this, there is a need for a data structure that can be
> initialized prior to invoking any SMC or MDT functions. This structure
> allows those functions to determine whether they are operating in the
> presence or absence of the Gunyah hypervisor and behave accordingly.
>
> Currently, remoteproc and non-remoteproc subsystems use different
> variants of the MDT loader helper API, primarily due to differences in
> metadata context handling. Remoteproc subsystems retain the metadata
> context until authentication and reset are completed, while
> non-remoteproc subsystems (e.g., video, graphics, IPA, etc.) do not
> retain the metadata context and can free it within the
> qcom_scm_pas_init() call by passing a NULL context parameter and due to
> these differences, it is not possible to extend metadata context
> handling to support remoteproc and non remoteproc subsystem use PAS
> operations, when Linux operates at EL2.
>
> Add PAS context data structure and initialization helper function.
>
> Signed-off-by: Mukesh Ojha <[email protected]>
> ---
> drivers/firmware/qcom/qcom_scm.c | 32 ++++++++++++++++++++++++++++++++
> include/linux/firmware/qcom/qcom_scm.h | 12 ++++++++++++
> 2 files changed, 44 insertions(+)
>
> diff --git a/drivers/firmware/qcom/qcom_scm.c
> b/drivers/firmware/qcom/qcom_scm.c
> index 0a0c48fca7cf..e4eb7f3ab7a5 100644
> --- a/drivers/firmware/qcom/qcom_scm.c
> +++ b/drivers/firmware/qcom/qcom_scm.c
> @@ -558,6 +558,38 @@ static void qcom_scm_set_download_mode(u32 dload_mode)
> dev_err(__scm->dev, "failed to set download mode: %d\n", ret);
> }
>
> +/**
> + * devm_qcom_scm_pas_context_init() - Initialize 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
> + *
> + * Upon successful, returns the PAS context or ERR_PTR() of the error
> otherwise.
> + */
> +void *devm_qcom_scm_pas_context_init(struct device *dev, u32 pas_id,
> phys_addr_t mem_phys,
Why does this return void* rather than struct qcom_scm_pas_context *?
> + size_t mem_size)
> +{
> + struct qcom_scm_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_scm_pas_context_init);
Thanks,
Stephan
