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[net-next,02/16] dt-bindings: net: dwmac: Extend number of PBL values

Message ID 20230313225103.30512-3-Sergey.Semin@baikalelectronics.ru (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series dt-bindings: net: dwmac: Extend clocks, props desc and constraints | expand

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Context Check Description
netdev/tree_selection success Clearly marked for net-next
netdev/apply fail Patch does not apply to net-next

Commit Message

Serge Semin March 13, 2023, 10:50 p.m. UTC
In accordance with [1] the permitted PBL values can be set as one of [1,
2, 4, 8, 16, 32]. The rest of the values result in undefined behavior. At
the same time some of the permitted values can be also invalid depending
on the controller FIFOs size and the data bus width. Due to having too
many variables all the possible PBL property constraints can't be
implemented in the bindings schema, let's extend the set of permitted PBL
values to be as much as the configuration register supports leaving the
undefined behaviour cases for developers to handle.

[1] DesignWare Cores Ethernet MAC Universal Databook, Revision 3.73a,
    October 2013, p. 380.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Rob Herring <robh@kernel.org>

---

Changelog v1:
- Use correct syntax of the JSON pointers, so the later would begin
  with a '/' after the '#'.
---
 Documentation/devicetree/bindings/net/snps,dwmac.yaml | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/net/snps,dwmac.yaml b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
index a0a0437eb4f0..fb9b8506a48f 100644
--- a/Documentation/devicetree/bindings/net/snps,dwmac.yaml
+++ b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
@@ -428,23 +428,26 @@  properties:
 
   snps,pbl:
     description:
-      Programmable Burst Length (tx and rx)
+      Programmable Burst Length (tx and rx). Note some of these values
+      can be still invalid due to HW limitations connected with the data
+      bus width and the FIFOs depth, so a total length of a single DMA
+      burst shouldn't exceed half the FIFO depth.
     $ref: /schemas/types.yaml#/definitions/uint32
-    enum: [2, 4, 8]
+    enum: [1, 2, 4, 8, 16, 32]
 
   snps,txpbl:
     description:
       Tx Programmable Burst Length. If set, DMA tx will use this
       value rather than snps,pbl.
     $ref: /schemas/types.yaml#/definitions/uint32
-    enum: [2, 4, 8]
+    enum: [1, 2, 4, 8, 16, 32]
 
   snps,rxpbl:
     description:
       Rx Programmable Burst Length. If set, DMA rx will use this
       value rather than snps,pbl.
     $ref: /schemas/types.yaml#/definitions/uint32
-    enum: [2, 4, 8]
+    enum: [1, 2, 4, 8, 16, 32]
 
   snps,no-pbl-x8:
     $ref: /schemas/types.yaml#/definitions/flag