netdev - Re: [PATCH] powerpc/kmcent2: update the ethernet devices' phy properties

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Date:   Sat, 14 Sep 2019 09:29:51 -0500
From:   Scott Wood <oss@...error.net>
To:     Madalin-cristian Bucur <madalin.bucur@....com>,
        Valentin Longchamp <valentin@...gchamp.me>
Cc:     "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "galak@...nel.crashing.org" <galak@...nel.crashing.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] powerpc/kmcent2: update the ethernet devices' phy
 properties

On Thu, 2019-08-29 at 11:25 +0000, Madalin-cristian Bucur wrote:
> > -----Original Message-----
> > From: Scott Wood <oss@...error.net>
> > Sent: Wednesday, August 28, 2019 7:19 AM
> > To: Valentin Longchamp <valentin@...gchamp.me>; Madalin-cristian Bucur
> > <madalin.bucur@....com>
> > Cc: linuxppc-dev@...ts.ozlabs.org; galak@...nel.crashing.org;
> > netdev@...r.kernel.org
> > Subject: Re: [PATCH] powerpc/kmcent2: update the ethernet devices' phy
> > properties
> > 
> > On Thu, 2019-08-08 at 23:09 +0200, Valentin Longchamp wrote:
> > > Le mar. 30 juil. 2019 à 11:44, Madalin-cristian Bucur
> > > <madalin.bucur@....com> a écrit :
> > > > 
> > > > > -----Original Message-----
> > > > > 
> > > > > > Le dim. 14 juil. 2019 à 22:05, Valentin Longchamp
> > > > > > <valentin@...gchamp.me> a écrit :
> > > > > > > 
> > > > > > > Change all phy-connection-type properties to phy-mode that are
> > > > > > > better
> > > > > > > supported by the fman driver.
> > > > > > > 
> > > > > > > Use the more readable fixed-link node for the 2 sgmii links.
> > > > > > > 
> > > > > > > Change the RGMII link to rgmii-id as the clock delays are added
> > 
> > by
> > > > > > > the
> > > > > > > phy.
> > > > > > > 
> > > > > > > Signed-off-by: Valentin Longchamp <valentin@...gchamp.me>
> > > > > 
> > > > > I don't see any other uses of phy-mode in arch/powerpc/boot/dts/fsl,
> > 
> > and
> > > > > I see
> > > > > lots of phy-connection-type with fman.  Madalin, does this patch
> > 
> > look
> > > > > OK?
> > > > > 
> > > > > -Scott
> > > > 
> > > > Hi,
> > > > 
> > > > we are using "phy-connection-type" not "phy-mode" for the NXP (former
> > > > Freescale)
> > > > DPAA platforms. While the two seem to be interchangeable ("phy-mode"
> > 
> > seems
> > > > to be
> > > > more recent, looking at the device tree bindings), the driver code in
> > > > Linux seems
> > > > to use one or the other, not both so one should stick with the variant
> > 
> > the
> > > > driver
> > > > is using. To make things more complex, there may be dependencies in
> > > > bootloaders,
> > > > I see code in u-boot using only "phy-connection-type" or only "phy-
> > 
> > mode".
> > > > 
> > > > I'd leave "phy-connection-type" as is.
> > > 
> > > So I have finally had time to have a look and now I understand what
> > > happens. You are right, there are bootloader dependencies: u-boot
> > > calls fdt_fixup_phy_connection() that somehow in our case adds (or
> > > changes if already in the device tree) the phy-connection-type
> > > property to a wrong value ! By having a phy-mode in the device tree,
> > > that is not changed by u-boot and by chance picked up by the kernel
> > > fman driver (of_get_phy_mode() ) over phy-connection-mode, the below
> > > patch fixes it for us.
> > > 
> > > I agree with you, it's not correct to have both phy-connection-type
> > > and phy-mode. Ideally, u-boot on the board should be reworked so that
> > > it does not perform the above wrong fixup. However, in an "unfixed"
> > > .dtb (I have disabled fdt_fixup_phy_connection), the device tree in
> > > the end only has either phy-connection-type or phy-mode, according to
> > > what was chosen in the .dts file. And the fman driver works well with
> > > both (thanks to the call to of_get_phy_mode() ). I would therefore
> > > argue that even if all other DPAA platforms use phy-connection-type,
> > > phy-mode is valid as well. (Furthermore we already have hundreds of
> > > such boards in the field and we don't really support "remote" u-boot
> > > update, so the u-boot fix is going to be difficult for us to pull).
> > > 
> > > Valentin
> > 
> > Madalin, are you OK with the patch given this explanation?
> > 
> > -Scott
> > 
> 
> Yes, I understand that it's the only option they have, given the inability
> to upgrade u-boot (this may prove to be an issue in the future, in other
> situations).
> 
> Acked-by: Madalin Bucur <madalin.bucur@....com>

Acked-by: Scott Wood <oss@...error.net>

-Scott