linux-kernel - Re: [PATCH v2] net: phy: marvell: Honor phy LED set by system firmware on a Dell hardware

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Date:   Fri, 21 Jan 2022 22:17:18 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     hkallweit1@...il.com, linux@...linux.org.uk,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: phy: marvell: Honor phy LED set by system
 firmware on a Dell hardware

On Fri, Jan 21, 2022 at 9:22 PM Andrew Lunn <andrew@...n.ch> wrote:
>
> On Fri, Jan 21, 2022 at 12:01:35PM +0800, Kai-Heng Feng wrote:
> > On Thu, Jan 20, 2022 at 10:26 PM Andrew Lunn <andrew@...n.ch> wrote:
> > >
> > > On Thu, Jan 20, 2022 at 01:19:29PM +0800, Kai-Heng Feng wrote:
> > > > BIOS on Dell Edge Gateway 3200 already makes its own phy LED setting, so
> > > > instead of setting another value, keep it untouched and restore the saved
> > > > value on system resume.
> > > >
> > > > Introduce config_led() callback in phy_driver() to make the implemtation
> > > > generic.
> > >
> > > I'm also wondering if we need to take a step back here and get the
> > > ACPI guys involved. I don't know much about ACPI, but shouldn't it
> > > provide a control method to configure the PHYs LEDs?
> > >
> > > We already have the basics for defining a PHY in ACPI. See:
> > >
> > > https://www.kernel.org/doc/html/latest/firmware-guide/acpi/dsd/phy.html
> >
> > These properties seem to come from device-tree.
>
> They are similar to what DT has, but expressed in an ACPI way. DT has
> been used with PHY drivers for a long time, but ACPI is new. The ACPI
> standard also says nothing about PHYs. So Linux has defined its own
> properties, which we expect all ACPI machine to use. According to the
> ACPI maintainers, this is within the ACPI standard. Maybe at some
> point somebody will submit the current definitions to the standards
> body for approval, or maybe the standard will do something completely
> different, but for the moment, this is what we have, and what you
> should use.

Right, so we can add a new property, document it, and just use it?
Maybe others will use the new property once we set the precedence?

>
> > > so you could extend this to include a method to configure the LEDs for
> > > a specific PHY.
> >
> > How to add new properties? Is it required to add new properties to
> > both DT and ACPI?
>
> Since all you are adding is a boolean, 'Don't touch the PHY LED
> configuration', it should be easy to do for both.

If adding a brand new property is acceptable, let me discuss it the vendor.

>
> What is interesting for Marvell PHYs is WoL, which is part of LED
> configuration. I've not checked, but i guess there are other PHYs
> which reuse LED output for a WoL interrupt. So it needs to be clearly
> defined if we expect the BIOS to also correctly configure WoL, or if
> Linux is responsible for configuring WoL, even though it means
> changing the LED configuration.

How about what Heiner proposed? Maybe we should leave the LED as is,
and restore it on system resume?

Kai-Heng

>
>          Andrew