On Thu, Nov 13, 2025 at 12:57:08PM +0100, Stephan Gerhold wrote:
> 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 *?
I kept it similar to align with other devm_* api, however, I can change it to
struct qcom_scm_pas_context if it looks more reasonable.
>
> > + 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
--
-Mukesh Ojha
