Re: [PATCH 1/2] dt-bindings: net: rockchip-dwmac: add rk3568 xpcs compatible

From: "Heiko Stübner" <heiko@sntech.de>
To: Chukun Pan <amadeus@jmu.edu.cn>,
	"David S . Miller" <davem@davemloft.net>,
	Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Jose Abreu <joabreu@synopsys.com>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	David Wu <david.wu@rock-chips.com>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	netdev@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/2] dt-bindings: net: rockchip-dwmac: add rk3568 xpcs compatible
Date: Tue, 29 Nov 2022 11:22:28 +0100	[thread overview]
Message-ID: <3689593.Mh6RI2rZIc@diego> (raw)
In-Reply-To: <8eb78282-08c2-24bf-4049-5c610dd781fc@linaro.org>

Am Dienstag, 29. November 2022, 10:59:34 CET schrieb Krzysztof Kozlowski:
> On 29/11/2022 10:56, Heiko Stübner wrote:
> > Am Dienstag, 29. November 2022, 09:49:08 CET schrieb Krzysztof Kozlowski:
> >> On 29/11/2022 08:27, Chukun Pan wrote:
> >>> The gmac of RK3568 supports RGMII/SGMII/QSGMII interface.
> >>> This patch adds a compatible string for the required clock.
> >>>
> >>> Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
> >>> ---
> >>>  Documentation/devicetree/bindings/net/rockchip-dwmac.yaml | 6 ++++++
> >>>  1 file changed, 6 insertions(+)
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/net/rockchip-dwmac.yaml b/Documentation/devicetree/bindings/net/rockchip-dwmac.yaml
> >>> index 42fb72b6909d..36b1e82212e7 100644
> >>> --- a/Documentation/devicetree/bindings/net/rockchip-dwmac.yaml
> >>> +++ b/Documentation/devicetree/bindings/net/rockchip-dwmac.yaml
> >>> @@ -68,6 +68,7 @@ properties:
> >>>          - mac_clk_rx
> >>>          - aclk_mac
> >>>          - pclk_mac
> >>> +        - pclk_xpcs
> >>>          - clk_mac_ref
> >>>          - clk_mac_refout
> >>>          - clk_mac_speed
> >>> @@ -90,6 +91,11 @@ properties:
> >>>        The phandle of the syscon node for the peripheral general register file.
> >>>      $ref: /schemas/types.yaml#/definitions/phandle
> >>>  
> >>> +  rockchip,xpcs:
> >>> +    description:
> >>> +      The phandle of the syscon node for the peripheral general register file.
> >>
> >> You used the same description as above, so no, you cannot have two
> >> properties which are the same. syscons for GRF are called
> >> "rockchip,grf", aren't they?
> > 
> > Not necessarily :-) .
> 
> OK, then description should have something like "...GRF for foo bar".

Actually looking deeper in the TRM, having these registers "just" written
to from the dwmac-glue-layer feels quite a bit like a hack.

The "pcs" thingy referenced in patch2 actually looks more like a real device
with its own section in the TRM and own iomem area. This pcs device then
itself has some more settings stored in said pipe-grf.

So this looks more like it wants to be an actual phy-driver.

@Chukun Pan: plase take a look at something like
https://elixir.bootlin.com/linux/latest/source/drivers/phy/mscc/phy-ocelot-serdes.c#L398
on how phy-drivers for ethernets could look like.

Aquiring such a phy from the dwmac-glue and calling phy_set_mode after
moving the xpcs_setup to a phy-driver shouldn't be too hard I think.

The qsgmii/sgmii_pcs list of registers in the TRM alone already takes up
4 A4 pages, so while using the PCS as syscon and just writing some values
into it might work now, this doesn't feel at all like a future-save handling.

Heiko

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