firmware: qcom_scm: Add a prep version of auth_and_reset function

For memory passed to TrustZone (TZ), it must either be part of a pool
registered with TZ or explicitly registered via SHMbridge SMC calls.
When Gunyah hypervisor is present, PAS SMC calls from Linux running at
EL1 are trapped by Gunyah running @ EL2, which handles SHMbridge
creation for both metadata and remoteproc carveout memory before
invoking the calls to TZ.

On SoCs running with a non-Gunyah-based hypervisor, Linux must take
responsibility for creating the SHM bridge before invoking PAS SMC
calls. For the auth_and_reset() call, the remoteproc carveout memory
must first be registered with TZ via a SHMbridge SMC call and once
authentication and reset are complete, the SHMbridge memory can be
deregistered.

Introduce qcom_scm_pas_prepare_and_auth_reset(), which sets up the SHM
bridge over the remoteproc carveout memory when Linux operates at EL2.
This behavior is indicated by a new field added to the PAS context data
structure. The function then invokes the auth_and_reset SMC call.

Signed-off-by: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20260105-kvmrprocv10-v10-8-022e96815380@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

1 files changed, 47 insertions, 0 deletions

diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c
index 4edd475ef848..d3783166fea1 100644
--- a/drivers/firmware/qcom/qcom_scm.c
+++ b/drivers/firmware/qcom/qcom_scm.c
@@ -766,6 +766,53 @@ disable_clk:
 EXPORT_SYMBOL_GPL(qcom_scm_pas_auth_and_reset);
 
 /**
+ * qcom_scm_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_scm_pas_prepare_and_auth_reset(struct qcom_scm_pas_context *ctx)
+{
+	u64 handle;
+	int ret;
+
+	/*
+	 * When Linux running @ EL1, Gunyah hypervisor running @ EL2 traps the
+	 * auth_and_reset call and create an shmbridge on the remote subsystem
+	 * memory region and then invokes a call to TrustZone to authenticate.
+	 */
+	if (!ctx->use_tzmem)
+		return qcom_scm_pas_auth_and_reset(ctx->pas_id);
+
+	/*
+	 * When Linux runs @ EL2 Linux must create the shmbridge itself and then
+	 * subsequently call TrustZone for authenticate and reset.
+	 */
+	ret = qcom_tzmem_shm_bridge_create(ctx->mem_phys, ctx->mem_size, &handle);
+	if (ret)
+		return ret;
+
+	ret = qcom_scm_pas_auth_and_reset(ctx->pas_id);
+	qcom_tzmem_shm_bridge_delete(handle);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(qcom_scm_pas_prepare_and_auth_reset);
+
+/**
  * qcom_scm_pas_shutdown() - Shut down the remote processor
  * @pas_id:	peripheral authentication service id
  *