Message-ID: <pbh7gh7fkfis7zqqmmug5wtosq3xsx7z3ktsfg3jy6jthm6qva@a3wy7knv2vcr>
Date:   Mon, 28 Aug 2023 18:51:49 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Jisheng Zhang <jszhang@...nel.org>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>, Maxime@....codeaurora.org,
        Coquelin@....codeaurora.org,
        Simon Horman <simon.horman@...igine.com>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH net-next v2 2/3] dt-bindings: net: add T-HEAD dwmac
 support

On Mon, Aug 28, 2023 at 11:17:36PM +0800, Jisheng Zhang wrote:
> On Mon, Aug 28, 2023 at 04:13:00PM +0300, Serge Semin wrote:
> > On Sun, Aug 27, 2023 at 05:17:09PM +0800, Jisheng Zhang wrote:
> > > Add documentation to describe T-HEAD dwmac.
> > > 
> > > Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
> > > ---
> > >  .../devicetree/bindings/net/snps,dwmac.yaml   |  1 +
> > >  .../devicetree/bindings/net/thead,dwmac.yaml  | 77 +++++++++++++++++++
> > >  2 files changed, 78 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/net/thead,dwmac.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/net/snps,dwmac.yaml b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> > > index b196c5de2061..73821f86a609 100644
> > > --- a/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> > > +++ b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> > > @@ -96,6 +96,7 @@ properties:
> > >          - snps,dwxgmac
> > >          - snps,dwxgmac-2.10
> > >          - starfive,jh7110-dwmac
> > > +        - thead,th1520-dwmac
> > >  
> > >    reg:
> > >      minItems: 1
> > > diff --git a/Documentation/devicetree/bindings/net/thead,dwmac.yaml b/Documentation/devicetree/bindings/net/thead,dwmac.yaml
> > > new file mode 100644
> > > index 000000000000..bf8ec8ca2753
> > > --- /dev/null
> > 
> > > +++ b/Documentation/devicetree/bindings/net/thead,dwmac.yaml
> > 
> > see further regarding using dwmac in the names here.
> > 
> > > @@ -0,0 +1,77 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/net/thead,dwmac.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > 
> > > +title: T-HEAD DWMAC Ethernet controller
> > 
> > Additionally would be nice to have a brief controller "description:"
> > having the next info: the SoCs the controllers can be found on, the DW
> > (G)MAC IP-core version the ethernet controller is based on and some
> > data about the synthesize parameters: SMA (MDIO-bus), Tx/Rx COE, DMA
> > FIFOs size, perfect and hash MAC-filters size, L3L4 frame filters
> > availability, VLAN hash filter, SA/VLAN-tag insertion, ARP offload
> > engine, PHY interfaces (MII, RMII, RGMII, etc), EEE support, IEEE
> > 1588(-2008) Timestamping support, PMT and Wake-up frame support, MAC
> > Management counters (MMC). In addition to that for DW QoS
> > ETH/XGMAC/XLGMAC the next info would be useful: number of MTL Queues
> > and DMA channels, MTL queues capabilities (QoS-related), TSO
> > availability, SPO availability.
> > 

> > Note DMA FIFO sizes can be also constrained in the properties
> > "rx-fifo-depth" and "tx-fifo-depth"; perfect and hash MAC-filter sizes -
> > in "snps,perfect-filter-entries" and "snps,multicast-filter-bins".

BTW plus to this you may wish to add the "rx-internal-delay-ps" and
"tx-internal-delay-ps" properties constraints seeing they device
supports internal Tx/Rx delays.

> 
> Hi Serge,
> 

> Thank you for your code review. I have different views here: If we
> only support the gmac controller in one specific SoC, these detailed
> information is nice to have, but what about if the driver/dt-binding
> supports the gmac controller in different SoCs? These detailed
> information will be outdated.

First they won't. Second then you can either add more info to the
description for instance in a separate paragraph or create a dedicated
DT-bindings. Such information would be very much useful for the
generic STMMAC driver code maintenance.

> 
> what's more, I think the purpose of dt-binding is different from
> the one of documentation.

The purpose of the DT-bindings is a hardware "description". The info I
listed describes your hardware.

> 
> So I prefer to put these GMAC IP related detailed information into
> the SoC's dtsi commit msg rather than polluting the dt-binding.
> > 
> > > +
> > > +maintainers:
> > > +  - Jisheng Zhang <jszhang@...nel.org>
> > > +
> > > +select:
> > > +  properties:
> > > +    compatible:
> > > +      contains:
> > > +        enum:
> > 
> > > +          - thead,th1520-dwmac
> > 
> > Referring to the DW IP-core in the compatible string isn't very
> > much useful especially seeing you have a generic fallback compatible.
> > Name like "thead,th1520-gmac" looks more informative indicating its
> > speed capability.
> 

> This is just to follow the common style as those dwmac-* does.
> I'm not sure which is better, but personally, I'd like to keep current
> common style.

It's not that common. Half the compatible strings use the notation
suggested by me and it has more sense then a dwmac suffix. It's ok to
use the suffix in the STMMAC driver-related things because the glue
code is supposed to work with the DW *MAC generic code. Using it in
the compatible string especially together with the generic fallback
compatible just useless.

-Serge(y)

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