netdev - Re: [EXT] Re: [PATCH] net: stmmac: dwmac-imx: pause the TXC clock in fixed-link

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Date: Wed, 26 Jul 2023 17:29:30 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Shenwei Wang <shenwei.wang@....com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Shawn Guo <shawnguo@...nel.org>, dl-linux-imx <linux-imx@....com>,
	Giuseppe Cavallaro <peppe.cavallaro@...com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Jose Abreu <joabreu@...opsys.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-stm32@...md-mailman.stormreply.com" <linux-stm32@...md-mailman.stormreply.com>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	Frank Li <frank.li@....com>
Subject: Re: [EXT] Re: [PATCH] net: stmmac: dwmac-imx: pause the TXC clock in
 fixed-link

On Wed, Jul 26, 2023 at 04:10:11PM +0000, Shenwei Wang wrote:
> > So, plat->phy_node will never ever be equal to your "dn" above.
> > plat->phylink_node is the same as dwmac->dev->of_node above, and
> > so plat->phylink_node will never be your "dn" above either.
> >
> > Those two together means that imx_dwmac_is_fixed_link() will _always_ return
> > false, and thus most of the code you're adding is rather useless.
> >
> > It also means the code you're submitting probably hasn't been properly tested.
> >
> > Have you confirmed that imx_dwmac_is_fixed_link() will actually return true in
> > your testing? Under what conditions did your testing reveal a true return value
> > from this function?
> >
> 
> We can't make that assumption. In my testing code, I had trace statements in that
> section to indicate the code was actually executed. You may get some clues from the following DTS:
> 
> +&eqos {
> +       pinctrl-names = "default";
> +       pinctrl-0 = <&pinctrl_eqos_rgmii>;
> +       phy-mode = "rgmii-rxid";
> +       phy-handle = <&fixed0>;
> +       status = "okay";
> +
> +       fixed0: fixed-link {
> +               speed = <1000>;
> +               full-duplex;
> +       };

This is just totally botched up.

"fixed0" is _not_ a PHY, therefore you should NOT be referencing it
in phy-handle. Please see the DT binding document:

  phy-handle:
    $ref: /schemas/types.yaml#/definitions/phandle
    description:
      Specifies a reference to a node representing a PHY device.

  fixed-link:
    oneOf:
      - $ref: /schemas/types.yaml#/definitions/uint32-array
        deprecated: true
...
      - type: object
        additionalProperties: false
        properties:
          speed:
...

As I said, fixed-link is _not_ a PHY, and thus phy-handle must *not*
be used to point at it.

The mere presence of a node called "fixed-link" will make this "eqos"
device use that fixed-link node, and the phy-handle will be ignored.

So sorry, but as far as your patch goes, it's a hard NAK from me
right now until the DT description is actually correct.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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