netdev - [PATCH 02/25] dt-bindings: net: dwmac: Extend number of PBL values

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Date:   Mon, 14 Dec 2020 12:15:52 +0300
From:   Serge Semin <Sergey.Semin@...kalelectronics.ru>
To:     Rob Herring <robh+dt@...nel.org>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Johan Hovold <johan@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Joao Pinto <jpinto@...opsys.com>,
        Lars Persson <larper@...s.com>
CC:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Vyacheslav Mitrofanov 
        <Vyacheslav.Mitrofanov@...kalelectronics.ru>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        <netdev@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 02/25] dt-bindings: net: dwmac: Extend number of PBL values

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 results 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.
Seeing 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@...kalelectronics.ru>
---
 Documentation/devicetree/bindings/net/snps,dwmac.yaml | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/net/snps,dwmac.yaml b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
index 4b672499f20d..e084fbbf976e 100644
--- a/Documentation/devicetree/bindings/net/snps,dwmac.yaml
+++ b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
@@ -264,23 +264,26 @@ 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
-- 
2.29.2