From: Thierry Reding treding@nvidia.com
The Video Protection Region (VPR) found on NVIDIA Tegra chips is a region of memory that is protected from CPU accesses. It is used to decode and play back DRM protected content.
It is a standard reserved memory region that can exist in two forms: static VPR where the base address and size are fixed (uses the "reg" property to describe the memory) and a resizable VPR where only the size is known upfront and the OS can allocate it wherever it can be accomodated.
Reviewed-by: Rob Herring (Arm) robh@kernel.org Signed-off-by: Thierry Reding treding@nvidia.com --- Changes in v2: - add examples for fixed and resizable VPR --- .../nvidia,tegra-video-protection-region.yaml | 76 ++++++++++++++++++++++ 1 file changed, 76 insertions(+)
diff --git a/Documentation/devicetree/bindings/reserved-memory/nvidia,tegra-video-protection-region.yaml b/Documentation/devicetree/bindings/reserved-memory/nvidia,tegra-video-protection-region.yaml new file mode 100644 index 000000000000..1c524bae9ce3 --- /dev/null +++ b/Documentation/devicetree/bindings/reserved-memory/nvidia,tegra-video-protection-region.yaml @@ -0,0 +1,76 @@ +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/reserved-memory/nvidia,tegra-video-protection-... +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: NVIDIA Tegra Video Protection Region (VPR) + +maintainers: + - Thierry Reding thierry.reding@gmail.com + - Jon Hunter jonathanh@nvidia.com + +description: | + NVIDIA Tegra chips have long supported a mechanism to protect a single, + contiguous memory region from non-secure memory accesses. Typically this + region is used for decoding and playback of DRM protected content. Various + devices, such as the display controller and multimedia engines (video + decoder) can access this region in a secure way. Access from the CPU is + generally forbidden. + + Two variants exist for VPR: one is fixed in both the base address and size, + while the other is resizable. Fixed VPR can be described by just a "reg" + property specifying the base address and size, whereas the resizable VPR + is defined by a size/alignment pair of properties. For resizable VPR the + memory is reusable by the rest of the system when it's unused for VPR and + therefore the "reusable" property must be specified along with it. For a + fixed VPR, the memory is permanently protected, and therefore it's not + reusable and must also be marked as "no-map" to prevent any (including + speculative) accesses to it. + +allOf: + - $ref: reserved-memory.yaml + +properties: + compatible: + const: nvidia,tegra-video-protection-region + +dependencies: + size: [alignment, reusable] + alignment: [size, reusable] + reusable: [alignment, size] + + reg: [no-map] + no-map: [reg] + +unevaluatedProperties: false + +oneOf: + - required: + - compatible + - reg + + - required: + - compatible + - size + +examples: + - | + /* resizable VPR */ + protected { + compatible = "nvidia,tegra-video-protection-region"; + + size = <0x0 0x70000000>; + alignment = <0x0 0x100000>; + reusable; + }; + + - | + /* fixed VPR */ + protected@2a8000000 { + compatible = "nvidia,tegra-video-protection-region"; + + /* fixed VPR */ + reg = <0x2 0xa8000000 0x0 0x70000000>; + no-map; + };