netdev - Re: [PATCH net-next v10 6/6] net: dt-bindings: dwmac: add support for mt8195

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Date:   Tue, 11 Jan 2022 17:36:55 -0600
From:   Rob Herring <robh@...nel.org>
To:     Biao Huang <biao.huang@...iatek.com>
Cc:     srv_heupstream <srv_heupstream@...iatek.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        David Miller <davem@...emloft.net>,
        "moderated list:ARM/STM32 ARCHITECTURE" 
        <linux-stm32@...md-mailman.stormreply.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        netdev <netdev@...r.kernel.org>, dkirjanov@...e.de,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Macpaul Lin <macpaul.lin@...iatek.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        devicetree@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH net-next v10 6/6] net: dt-bindings: dwmac: add support for mt8195

On Thu, Dec 16, 2021 at 8:06 PM Biao Huang <biao.huang@...iatek.com> wrote:
>
> Dear Rob,
>   Thanks for your comments~
>
>   For mt8195, the eth device node will look like:
>   eth: ethernet@...21000 {
>     compatible = "mediatek,mt8195-gmac", "snps,dwmac-5.10a";
>     ...
>     clock-names = "axi",
>                   "apb",
>                   "mac_cg",
>                   "mac_main",
>                   "ptp_ref",
>                   "rmii_internal";
>     clocks = <&pericfg_ao CLK_PERI_AO_ETHERNET>,
>              <&pericfg_ao CLK_PERI_AO_ETHERNET_BUS>,
>              <&pericfg_ao CLK_PERI_AO_ETHERNET_MAC>,
>              <&topckgen CLK_TOP_SNPS_ETH_250M>,
>              <&topckgen CLK_TOP_SNPS_ETH_62P4M_PTP>,
>              <&topckgen CLK_TOP_SNPS_ETH_50M_RMII>;
>     ...
>   }
>
> 1. "rmii_internal" is a special clock only required for
>    RMII phy interface, dwmac-mediatek.c will enable clocks
>    invoking clk_bulk_prepare_enable(xx, 6) for RMII,
>    and clk_bulk_prepare_enable(xx, 5) for other phy interfaces.
>    so, mt2712/mt8195 all put "rmii_internal" clock to the
>    end of clock list to simplify clock handling.
>
>    If I put mac_cg as described above, a if condition is required
> for clocks description in dt-binding, just like what I do in v7 send:
>   - if:
>       properties:
>         compatible:
>           contains:
>             enum:
>               - mediatek,mt2712-gmac
>
>     then:
>       properties:
>         clocks:
>           minItems: 5
>           items:
>             - description: AXI clock
>             - description: APB clock
>             - description: MAC Main clock
>             - description: PTP clock
>             - description: RMII reference clock provided by MAC
>
>         clock-names:
>           minItems: 5
>           items:
>             - const: axi
>             - const: apb
>             - const: mac_main
>             - const: ptp_ref
>             - const: rmii_internal
>
>   - if:
>       properties:
>         compatible:
>           contains:
>             enum:
>               - mediatek,mt8195-gmac
>
>     then:
>       properties:
>         clocks:
>           minItems: 6
>           items:
>             - description: AXI clock
>             - description: APB clock
>             - description: MAC clock gate
>             - description: MAC Main clock
>             - description: PTP clock
>             - description: RMII reference clock provided by MAC
>
>    This introduces some duplicated description.
>
> 2. If I put "mac_cg" to the end of clock list,
>    the dt-binding file can be simple just like
>    what we do in this v10 patch(need fix warnings reported by "make
> DT_CHECKER_FLAGS=-m dt_binding_check").
>
>    But for mt8195:
>      the eth node in dts should be modified,

I hope you are defining the binding before you use it... That's not
good practice and not a valid argument.

>      and eth driver clock handling will be complex;

How so?

Rob