From: Marc Kleine-Budde <mkl@pengutronix.de>
To: "Marek Behún" <kabel@kernel.org>
Cc: Rob Herring <robh+dt@kernel.org>,
devicetree@vger.kernel.org, Vladimir Oltean <olteanv@gmail.com>,
Holger Brunck <holger.brunck@hitachienergy.com>,
Andrew Lunn <andrew@lunn.ch>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Russell King <rmk+kernel@armlinux.org.uk>,
linux-phy@lists.infradead.org, Vinod Koul <vkoul@kernel.org>,
Kishon Vijay Abraham I <kishon@ti.com>,
ore@pengutronix.de, alexandru.tachici@analog.com
Subject: Re: [PATCH devicetree v3] dt-bindings: phy: Add `tx-p2p-microvolt` property binding
Date: Thu, 20 Jan 2022 20:50:51 +0100 [thread overview]
Message-ID: <20220120195051.pb4k24uazqqe6ecd@pengutronix.de> (raw)
In-Reply-To: <20220120190155.717f2d52@thinkpad>
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On 20.01.2022 19:01:55, Marek Behún wrote:
> On Thu, 20 Jan 2022 09:49:14 +0100
> Marc Kleine-Budde <mkl@pengutronix.de> wrote:
>
> > On 19.01.2022 14:11:17, Marek Behún wrote:
> > > Common PHYs and network PCSes often have the possibility to specify
> > > peak-to-peak voltage on the differential pair - the default voltage
> > > sometimes needs to be changed for a particular board.
> > >
> > > Add properties `tx-p2p-microvolt` and `tx-p2p-microvolt-names` for this
> > > purpose. The second property is needed to specify the mode for the
> > > corresponding voltage in the `tx-p2p-microvolt` property, if the voltage
> > > is to be used only for speficic mode. More voltage-mode pairs can be
> > > specified.
> > >
> > > Example usage with only one voltage (it will be used for all supported
> > > PHY modes, the `tx-p2p-microvolt-names` property is not needed in this
> > > case):
> > >
> > > tx-p2p-microvolt = <915000>;
> > >
> > > Example usage with voltages for multiple modes:
> > >
> > > tx-p2p-microvolt = <915000>, <1100000>, <1200000>;
> > > tx-p2p-microvolt-names = "2500base-x", "usb", "pcie";
> > >
> > > Add these properties into a separate file phy/transmit-amplitude.yaml,
> > > which should be referenced by any binding that uses it.
> >
> > If I understand your use-case correctly, you need different voltage p2p
> > levels in the connection between the Ethernet MAC and the Ethernet
> > switch or Ethernet-PHY?
>
> This is a SerDes differential pair amplitude. So yes to your question,
> if the MII interface uses differential pair, like sgmii, 10gbase-r, ...
>
> > Some of the two wire Ethernet standards (10base-T1S, 10base-T1L,
> > 100base-T1, 1000base-T1) defines several p2p voltage levels on the wire,
> > i.e. between the PHYs. Alexandru has posed a series where you can
> > specify the between-PHY voltage levels:
> >
> > | https://lore.kernel.org/all/20211210110509.20970-8-alexandru.tachici@analog.com/
>
> Copper ethernet is something different, so no conflict
>
> > Can we make clear that your binding specifies the voltage level on the
> > MII interface, in contrast Alexandru's binding?
>
> The binding explicitly says "common PHY", not ethernet PHY. I don't
> thing there will be any confusion. It can also be specified for USB3+
> differential pairs, or PCIe differential pairs, or DisplayPort
> differential pairs...
Thanks for the clarification.
regards,
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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next prev parent reply other threads:[~2022-01-20 19:51 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-19 13:11 [PATCH devicetree v3] dt-bindings: phy: Add `tx-p2p-microvolt` property binding Marek Behún
2022-01-20 8:49 ` Marc Kleine-Budde
2022-01-20 18:01 ` Marek Behún
2022-01-20 19:50 ` Marc Kleine-Budde [this message]
2022-01-21 19:18 ` Florian Fainelli
2022-02-05 2:18 ` Rob Herring
2022-02-05 3:18 ` Florian Fainelli
2022-02-06 17:54 ` Marek Behún
2022-02-07 5:29 ` Vinod Koul
2022-02-07 20:30 ` Rob Herring
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