[PATCH v4 0/1] dt-bindings: remoteproc: mtk,scp: Allow multiple memory regions for MT8188

[PATCH v4 0/1] dt-bindings: remoteproc: mtk,scp: Allow multiple memory regions for MT8188

[Arnab Layek]

This patch updates the mtk,scp dt-binding schema to support MT8188's
requirement for 1-2 memory regions while maintaining strict backward
compatibility for other MediaTek SoCs.

The MT8188 SCP requires a main SRAM region and optionally supports an
L1TCM (Level 1 Tightly Coupled Memory) region for performance
optimization. L1TCM is optional because basic SCP functionality works
with only SRAM, but L1TCM provides faster memory access when the board
hardware configuration includes it.

The base schema uses minItems: 1, maxItems: 2 (permissive range),
following the pattern established in other MediaTek dt-bindings like
mediatek,vcodec-encoder.yaml where the base accommodates all variants.
Conditionals then narrow the constraints per device.

Changes in v4:
- Improved commit message clarity per kernel submission guidelines:
  * Added bullet-point explanation of the two memory regions
  * Explained WHY L1TCM is optional (performance optimization, not
    required for basic functionality)
  * Explicitly listed which SoCs remain single-region
  * Clarified the two-conditional approach
  * Explained how minItems: 1 allows board-specific configuration
- Cover letter updated to explain L1TCM optional reasoning

Changes in v3:
- Removed "Tested on..." line (bindings cannot be tested)
- Added minItems: 1 to MT8188 conditional to make L1TCM truly optional
- Referenced mediatek,vcodec-encoder.yaml iommus pattern explicitly
- Base schema: minItems: 1, maxItems: 2 (permissive range)
- Non-MT8188: explicitly restricted to maxItems: 1
- MT8188: documented with item descriptions for both regions

Changes in v2:
- Added conditional schema for MT8188 to allow 1-2 memory regions
- Added descriptions for each memory region
- Did not work: base maxItems: 1 conflicted with conditional

Arnab Layek (1):
  dt-bindings: remoteproc: mtk,scp: Allow multiple memory regions for
    MT8188

 .../bindings/remoteproc/mtk,scp.yaml          | 45 ++++++++++++++++++-
 1 file changed, 43 insertions(+), 2 deletions(-)

-- 
2.45.2

[PATCH v4 1/1] dt-bindings: remoteproc: mtk,scp: Allow multiple memory regions for MT8188

[Arnab Layek]

The MT8188 SCP can use either one or two reserved memory regions:
- Required: Main SCP SRAM memory region (mandatory for SCP operation)
- Optional: SCP L1TCM memory region (Level 1 Tightly Coupled Memory,
  used for performance optimization when available, but not required
  for basic SCP functionality)

Other MediaTek SoCs (MT8183, MT8186, MT8192, MT8195) use only a single
memory region and must remain restricted to one region for backward
compatibility.

Update the base schema to allow 1-2 memory regions (minItems: 1,
maxItems: 2), following the pattern used by other MediaTek dt-bindings
like mediatek,vcodec-encoder.yaml where the base property defines a
permissive range accommodating all device variants.

Add two conditionals:
1. Explicitly restrict non-MT8188 devices to maxItems: 1
2. Document MT8188's two regions with descriptions (minItems: 1 makes
   the L1TCM region optional, allowing boards to specify 1-2 regions
   based on hardware configuration)

This approach maintains backward compatibility while enabling MT8188 to
specify 1-2 memory regions depending on board design and performance
requirements.

Signed-off-by: Arnab Layek <arnab.layek@mediatek.com>
---
 .../bindings/remoteproc/mtk,scp.yaml          | 45 ++++++++++++++++++-
 1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/remoteproc/mtk,scp.yaml b/Documentation/devicetree/bindings/remoteproc/mtk,scp.yaml
index bdbb12118da4..fca9b0675eae 100644
--- a/Documentation/devicetree/bindings/remoteproc/mtk,scp.yaml
+++ b/Documentation/devicetree/bindings/remoteproc/mtk,scp.yaml
@@ -55,7 +55,8 @@ properties:
       initializing SCP.
 
   memory-region:
-    maxItems: 1
+    minItems: 1
+    maxItems: 2
 
   cros-ec-rpmsg:
     $ref: /schemas/embedded-controller/google,cros-ec.yaml
@@ -123,7 +124,8 @@ patternProperties:
           initializing sub cores of multi-core SCP.
 
       memory-region:
-        maxItems: 1
+        minItems: 1
+        maxItems: 2
 
       cros-ec-rpmsg:
         $ref: /schemas/embedded-controller/google,cros-ec.yaml
@@ -205,6 +207,45 @@ allOf:
           items:
             - const: cfg
             - const: l1tcm
+  - if:
+      properties:
+        compatible:
+          enum:
+            - mediatek,mt8183-scp
+            - mediatek,mt8186-scp
+            - mediatek,mt8192-scp
+            - mediatek,mt8195-scp
+            - mediatek,mt8195-scp-dual
+    then:
+      properties:
+        memory-region:
+          maxItems: 1
+      patternProperties:
+        "^scp@[a-f0-9]+$":
+          properties:
+            memory-region:
+              maxItems: 1
+  - if:
+      properties:
+        compatible:
+          enum:
+            - mediatek,mt8188-scp
+            - mediatek,mt8188-scp-dual
+    then:
+      properties:
+        memory-region:
+          minItems: 1
+          items:
+            - description: Main SCP SRAM memory region
+            - description: Optional SCP L1TCM memory region
+      patternProperties:
+        "^scp@[a-f0-9]+$":
+          properties:
+            memory-region:
+              minItems: 1
+              items:
+                - description: Main SCP SRAM memory region
+                - description: Optional SCP L1TCM memory region
 
 additionalProperties: false
 
-- 
2.45.2

Re: [PATCH v4 1/1] dt-bindings: remoteproc: mtk,scp: Allow multiple memory regions for MT8188

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The dt-bindings are updated to allow MT8188 to provide L1TCM via a second `memory-region`, but the `mtk_scp` driver does not support parsing L1TCM from `memory-region`.
--

commit a5d9a931f3a31fccb0fec319f48f7f29be5209e8
Author: Arnab Layek <arnab.layek@mediatek.com>

dt-bindings: remoteproc: mtk,scp: Allow multiple memory regions for MT8188

This commit updates the MT8188 SCP binding to allow an optional second
memory region for Level 1 Tightly Coupled Memory. The base schema is
updated to allow up to two memory regions, keeping other devices
restricted to one region for backward compatibility.

> diff --git a/Documentation/devicetree/bindings/remoteproc/mtk,scp.yaml b/Documentation/devicetree/bindings/remoteproc/mtk,scp.yaml
> index bdbb12118da43..fca9b0675eae4 100644
> --- a/Documentation/devicetree/bindings/remoteproc/mtk,scp.yaml
> +++ b/Documentation/devicetree/bindings/remoteproc/mtk,scp.yaml

[ ... ]

> @@ -205,6 +207,45 @@ allOf:

[ ... ]

> +  - if:
> +      properties:
> +        compatible:
> +          enum:
> +            - mediatek,mt8188-scp
> +            - mediatek,mt8188-scp-dual
> +    then:
> +      properties:
> +        memory-region:
> +          minItems: 1
> +          items:
> +            - description: Main SCP SRAM memory region
> +            - description: Optional SCP L1TCM memory region

[Severity: Medium]
Are there regressions when the L1TCM region is specified as a memory-region
instead of a reg property?

Looking at the mtk_scp driver implementation, it appears to fetch L1TCM
exclusively by looking up an IORESOURCE_MEM resource named l1tcm, which
corresponds to the reg property rather than memory-region:

drivers/remoteproc/mtk_scp.c:scp_probe() {
    ...
    res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "l1tcm");
    if (res) {
        scp->l1tcm_base = devm_ioremap_resource(dev, res);
    ...
}

Since of_reserved_mem_device_init() typically only maps the first memory
region, and the driver checks the reg properties for l1tcm, could this
cause a regression where the second memory-region is silently ignored at
runtime, leaving the L1TCM performance optimizations non-functional?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260520112629.3420612-2-arnab.layek@mediatek.com?part=1