Re: [PATCH v4 2/3] dt-bindings: Add dma-channels for pdma device node

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On Sun, 16 Jan 2022 17:35:27 PST (-0800), zong.li@xxxxxxxxxx wrote:
Add dma-channels property, then we can determine how many channels there
by device tree, rather than statically defines it in PDMA driver

Maybe "statically defining it" is better here?


Signed-off-by: Zong Li <zong.li@xxxxxxxxxx>
---
 .../devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml    | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
index d32a71b975fe..3dbb8caefc17 100644
--- a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
+++ b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
@@ -34,6 +34,12 @@ properties:
     minItems: 1
     maxItems: 8

+  dma-channels:
+    description: For backwards-compatible, the default value is 4

Maybe "backwards-compatibility" is better here?

+    minimum: 1
+    maximum: 4
+    default: 4
+
   '#dma-cells':
     const: 1

@@ -50,6 +56,7 @@ examples:
     dma@3000000 {
       compatible = "sifive,fu540-c000-pdma";

IMO we should have a "sifive,pdma-1.0.0" (or whatever the versioning scheme ended up being) here, in addition to the SOC-specific DT entry. It's kind of odd to start extending the SOC-specific DT entry, as the whole idea there is to let us have an out in case we find future compatibility issues.

       reg = <0x3000000 0x8000>;
+      dma-channels = <4>;
       interrupts = <23 24 25 26 27 28 29 30>;
       #dma-cells = <1>;
     };



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