Add documentation for SMMUv3 driver in Hafnium(SPM)
Change-Id: I0b38c114fd2958d2b4040585611cafa132ccfd9c
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
diff --git a/docs/components/secure-partition-manager.rst b/docs/components/secure-partition-manager.rst
index 9a65e64..842345a 100644
--- a/docs/components/secure-partition-manager.rst
+++ b/docs/components/secure-partition-manager.rst
@@ -7,6 +7,8 @@
========
+--------+-----------------------------------+
+| DMA | Direct Memory Access |
++--------+-----------------------------------+
| DTB | Device Tree Blob |
+--------+-----------------------------------+
| DTS | Device Tree Source |
@@ -33,6 +35,8 @@
+--------+-----------------------------------+
| PSA | Platform Security Architecture |
+--------+-----------------------------------+
+| SMMU | System Memory Management Unit |
++--------+-----------------------------------+
| SP | Secure Partition |
+--------+-----------------------------------+
| SPM | Secure Partition Manager |
@@ -832,6 +836,114 @@
to the SPMC when the primary SP EC boots, or be supplied through the SP
manifest.
+Support for SMMUv3 in Hafnium
+=============================
+
+An SMMU is analogous to an MMU in a CPU. It performs address translations for
+Direct Memory Access (DMA) requests from system I/O devices.
+The responsibilities of an SMMU include:
+
+- Translation: Incoming DMA requests are translated from bus address space to
+ system physical address space using translation tables compliant to
+ Armv8/Armv7 VMSA descriptor format.
+- Protection: An I/O device can be prohibited from read, write access to a
+ memory region or allowed.
+- Isolation: Traffic from each individial device can be independently managed.
+ The devices are differentiated from each other using unique translation
+ tables.
+
+The following diagram illustrates a typical SMMU IP integrated in a SoC with
+several I/O devices along with Interconnect and Memory system.
+
+.. image:: ../resources/diagrams/MMU-600.png
+
+SMMU has several versions including SMMUv1, SMMUv2 and SMMUv3. Hafnium provides
+support for SMMUv3 driver in both Normal and Secure World. A brief introduction
+of SMMUv3 functionality and the corresponding software support in Hafnium is
+provided here.
+
+SMMUv3 features
+---------------
+
+- SMMUv3 provides Stage1, Stage2 translation as well as nested (Stage1 + Stage2)
+ translation support. It can either bypass or abort incoming translations as
+ well.
+- Traffic (memory transactions) from each upstream I/O peripheral device,
+ referred to as Stream, can be independently managed using a combination of
+ several memory based configuration structures. This allows the SMMUv3 to
+ support a large number of streams with each stream assigned to a unique
+ translation context.
+- Support for Armv8.1 VMSA where the SMMU shares the translation tables with
+ a Processing Element. AArch32(LPAE) and AArch64 translation table format
+ are supported by SMMUv3.
+- SMMUv3 offers non-secure stream support with secure stream support being
+ optional. Logically, SMMUv3 behaves as if there is an indepdendent SMMU
+ instance for secure and non-secure stream support.
+- It also supports sub-streams to differentiate traffic from a virtualized
+ peripheral associated with a VM/SP.
+- Additionally, SMMUv3.2 provides support for PEs implementing Armv8.4-A
+ extensions. Consequently, SPM depends on Secure EL2 support in SMMUv3.2
+ for providing Secure Stage2 translation support to upstream peripheral
+ devices.
+
+SMMUv3 Programming Interfaces
+-----------------------------
+
+SMMUv3 has three software interfaces that are used by the Hafnium driver to
+configure the behaviour of SMMUv3 and manage the streams.
+
+- Memory based data strutures that provide unique translation context for
+ each stream.
+- Memory based circular buffers for command queue and event queue.
+- A large number of SMMU configuration registers that are memory mapped during
+ boot time by Hafnium driver. Except a few registers, all configuration
+ registers have independent secure and non-secure versions to configure the
+ behaviour of SMMUv3 for translation of secure and non-secure streams
+ respectively.
+
+Peripheral device manifest
+--------------------------
+
+Currently, SMMUv3 driver in Hafnium only supports dependent peripheral devices.
+These devices are dependent on PE endpoint to initiate and receive memory
+management transactions on their behalf. The acccess to the MMIO regions of
+any such device is assigned to the endpoint during boot. Moreover, SMMUv3 driver
+uses the same stage 2 translations for the device as those used by partition
+manager on behalf of the PE endpoint. This ensures that the peripheral device
+has the same visibility of the physical address space as the endpoint. The
+device node of the corresponding partition manifest (refer to `[1]`_ section 3.2
+) must specify these additional properties for each peripheral device in the
+system :
+
+- smmu-id: This field helps to identify the SMMU instance that this device is
+ upstream of.
+- stream-ids: List of stream IDs assigned to this device.
+
+.. code:: shell
+
+ smmuv3-testengine {
+ base-address = <0x00000000 0x2bfe0000>;
+ pages-count = <32>;
+ attributes = <0x3>;
+ smmu-id = <0>;
+ stream-ids = <0x0 0x1>;
+ interrupts = <0x2 0x3>, <0x4 0x5>;
+ exclusive-access;
+ };
+
+SMMUv3 driver limitations
+-------------------------
+
+The primary design goal for the Hafnium SMMU driver is to support secure
+streams.
+
+- Currently, the driver only supports Stage2 translations. No support for
+ Stage1 or nested translations.
+- Supports only AArch64 translation format.
+- No support for features such as PCI Express (PASIDs, ATS, PRI), MSI, RAS,
+ Fault handling, Performance Monitor Extensions, Event Handling, MPAM.
+- No support for independent peripheral devices.
+
References
==========