[PATCH v3 01/13] dt-bindings: media: qcom,venus: Add context bank subnodes to common schema

[Vikash Garodia]

The VPU issues DMA through several SMMU streams, and the hardware does
not give every stream the same addressable range. The non-pixel stream
cannot address the low 600MB of IOVA space, while the pixel stream can
address the full range:
    +-----------------------------------------------------------+
    | non-pixel stream addressable range (600 MB - 3.5 GB)      |
    | 0x25800000 - 0xe0000000                                   |
    +-----------------------------------------------------------+
    | pixel stream addressable range (0 - 3.5 GB)               |
    | 0x00000000 - 0xe0000000                                   |
    +-----------------------------------------------------------+
A single "iommus" property on the video-codec node puts every stream in
one IOMMU domain sharing one IOVA allocator, so nothing restricts a
non-pixel buffer to avoid 0 to 600MB. Once an allocation lands below
that boundary the hardware faults, which shows up as unhandled SMMU page
faults and spontaneous reboots:
https://gitlab.freedesktop.org/drm/msm/-/work_items/100

Given that the address range restriction is for specific VPU stream, it
should be ideally be moved to that stream. To achieve the same, a subset
of streams is now represented as subnodes, so that each can be
associated with its respective addressable range. The design was
discussed and agreed by mainatiners here
https://lore.kernel.org/all/c7b956a9-d3e8-4e18-b780-5d08f5cd2ca1@xxxxxxxxxx

In the past, this limitation was addressed with an iommu-map approach,
with the iris driver dynamically creating the devices. That approach was
later concluded to be a hack to avoid having subnodes, and was NAKed by
the iommu maintainers. It was discussed in detail here:
https://lore.kernel.org/all/c7b956a9-d3e8-4e18-b780-5d08f5cd2ca1@xxxxxxxxxx/

"iommu-ranges" on the subnode describes the *allowed* IOVA range that
stream is allowed to use, so the IOVA is allocated from the specified
range only. Define all the possible subnodes so as to describe all the
VPU hardware iommu interfaces, both secure as well as non secure.

address-cells, size-cells and dma-ranges declares the 1:1 DMA
translation into the parent.

The parent "iommus" is kept as an alternative via "oneOf", so platforms
that have not been converted to subnodes still validate. New platforms
should use the subnode form.

This patch depends-on:
https://github.com/devicetree-org/dt-schema/pull/207

 Tested-by: Daniel J Blueman <daniel@xxxxxxxxx>
Signed-off-by: Vikash Garodia <vikash.garodia@xxxxxxxxxxxxxxxx>
---
 .../bindings/media/qcom,sc7180-venus.yaml          | 15 ----
 .../bindings/media/qcom,venus-common.yaml          | 97 ++++++++++++++++++++++
 2 files changed, 97 insertions(+), 15 deletions(-)

diff --git a/Documentation/devicetree/bindings/media/qcom,sc7180-venus.yaml b/Documentation/devicetree/bindings/media/qcom,sc7180-venus.yaml
index b21bed314848480b82153e49602f0b19e08e7335..bfd8b1ad473128c974bce84639cb0aff59d8c2cc 100644
--- a/Documentation/devicetree/bindings/media/qcom,sc7180-venus.yaml
+++ b/Documentation/devicetree/bindings/media/qcom,sc7180-venus.yaml
@@ -91,21 +91,6 @@ properties:
     deprecated: true
     additionalProperties: false
 
-  video-firmware:
-    type: object
-    additionalProperties: false
-
-    description: |
-      Firmware subnode is needed when the platform does not
-      have TrustZone.
-
-    properties:
-      iommus:
-        maxItems: 1
-
-    required:
-      - iommus
-
 required:
   - compatible
   - power-domain-names
diff --git a/Documentation/devicetree/bindings/media/qcom,venus-common.yaml b/Documentation/devicetree/bindings/media/qcom,venus-common.yaml
index 59a3fde846d2196ab1e4588eb396012ba6860712..68d5e592a028c5eecde04ce72cd5ae6815ba5c82 100644
--- a/Documentation/devicetree/bindings/media/qcom,venus-common.yaml
+++ b/Documentation/devicetree/bindings/media/qcom,venus-common.yaml
@@ -47,6 +47,93 @@ properties:
     minItems: 1
     maxItems: 4
 
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 1
+
+  dma-ranges:
+    maxItems: 1
+
+  non-pixel:
+    type: object
+    description:
+      Context bank for VPU non-pixel buffers, including compressed and internal buffers.
+    additionalProperties: false
+
+    properties:
+      iommus:
+        maxItems: 1
+      iommu-ranges:
+        maxItems: 1
+    required:
+      - iommus
+      - iommu-ranges
+
+  pixel:
+    type: object
+    description:
+      Context bank for VPU pixel buffers containing uncompressed video data.
+    additionalProperties: false
+
+    properties:
+      iommus:
+        maxItems: 1
+    required:
+      - iommus
+
+  video-firmware:
+    type: object
+    description:
+      Context bank for the VPU firmware processing domain.
+    additionalProperties: false
+
+    properties:
+      iommus:
+        maxItems: 1
+    required:
+      - iommus
+
+  secure-non-pixel:
+    type: object
+    description:
+      Context bank for VPU secure non-pixel buffers.
+    additionalProperties: false
+
+    properties:
+      iommus:
+        maxItems: 1
+      iommu-ranges:
+        maxItems: 1
+    required:
+      - iommus
+      - iommu-ranges
+
+  secure-pixel:
+    type: object
+    description:
+      Context bank for VPU secure pixel buffers containing uncompressed video data.
+    additionalProperties: false
+
+    properties:
+      iommus:
+        maxItems: 1
+    required:
+      - iommus
+
+  secure-bitstream:
+    type: object
+    description:
+      Context bank for VPU secure bitstream buffers containing compressed video data.
+    additionalProperties: false
+
+    properties:
+      iommus:
+        maxItems: 1
+    required:
+      - iommus
+
 required:
   - reg
   - clocks
@@ -55,4 +142,14 @@ required:
   - memory-region
   - power-domains
 
+oneOf:
+  - required:
+      - iommus
+  - required:
+      - '#address-cells'
+      - '#size-cells'
+      - dma-ranges
+      - non-pixel
+      - pixel
+
 additionalProperties: true

-- 
2.34.1