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Message-ID: <1f2bc5416a0a73756cc1f45f3300619eb201b0a4.camel@redhat.com>
Subject: Re: [PATCH net v3] net: dsa: mt7530: fix enabling EEE on MT7531
 switch on all boards
From: Paolo Abeni <pabeni@redhat.com>
To: arinc.unal@arinc9.com, Daniel Golle <daniel@makrotopia.org>, DENG
 Qingfang <dqfext@gmail.com>, Sean Wang <sean.wang@mediatek.com>, Andrew
 Lunn <andrew@lunn.ch>, Florian Fainelli <f.fainelli@gmail.com>, Vladimir
 Oltean <olteanv@gmail.com>, "David S. Miller" <davem@davemloft.net>, Eric
 Dumazet <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>, Matthias
 Brugger <matthias.bgg@gmail.com>, AngeloGioacchino Del Regno
 <angelogioacchino.delregno@collabora.com>, =?ISO-8859-1?Q?Ren=E9?= van
 Dorst <opensource@vdorst.com>, Russell King <linux@armlinux.org.uk>,
 SkyLake Huang <SkyLake.Huang@mediatek.com>, Heiner Kallweit
 <hkallweit1@gmail.com>
Cc: Bartel Eerdekens <bartel.eerdekens@constell8.be>,
 mithat.guner@xeront.com,  erkin.bozoglu@xeront.com, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org,  linux-arm-kernel@lists.infradead.org,
 linux-mediatek@lists.infradead.org,  Florian Fainelli
 <florian.fainelli@broadcom.com>
Date: Tue, 09 Apr 2024 13:58:56 +0200
In-Reply-To: <20240408-for-net-mt7530-fix-eee-for-mt7531-mt7988-v3-1-84fdef1f008b@arinc9.com>
References: 
	<20240408-for-net-mt7530-fix-eee-for-mt7531-mt7988-v3-1-84fdef1f008b@arinc9.com>
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On Mon, 2024-04-08 at 10:08 +0300, Ar=C4=B1n=C3=A7 =C3=9CNAL via B4 Relay w=
rote:
> From: Ar=C4=B1n=C3=A7 =C3=9CNAL <arinc.unal@arinc9.com>
>=20
> The commit 40b5d2f15c09 ("net: dsa: mt7530: Add support for EEE features"=
)
> brought EEE support but did not enable EEE on MT7531  MACs. EEE is
> enabled on MT7531 switch MACs by pulling the LAN2LED0 pin low on the boar=
d
> (bootstrapping), unsetting the EEE_DIS bit on the trap register, or setti=
ng
> the internal EEE switch bit on the CORE_PLL_GROUP4 register. Thanks to
> SkyLake Huang (=E9=BB=83=E5=95=9F=E6=BE=A4) from MediaTek for providing i=
nformation on the
> internal EEE switch bit.
>=20
> There are existing boards that were not designed to pull the pin low.
> Because of that, the EEE status currently depends on the board design.
>=20
> The EEE_DIS bit on the trap pertains to the LAN2LED0 pin which is usually
> used to control an LED. Once the bit is unset, the pin will be low. That
> will make the active low LED turn on. The pin is controlled by the switch
> PHY. It seems that the PHY controls the pin in the way that it inverts th=
e
> pin state. That means depending on the wiring of the LED connected to
> LAN2LED0 on the board, the LED may be on without an active link.
>=20
> To not cause this unwanted behaviour whilst enabling EEE on all boards, s=
et
> the internal EEE switch bit on the CORE_PLL_GROUP4 register.
>=20
> My testing on MT7531 shows a certain amount of traffic loss when EEE is
> enabled. That said, I haven't come across a board that enables EEE. So
> enable EEE on the switch MACs but disable EEE advertisement on the switch
> PHYs. This way, we don't change the behaviour of the majority of the boar=
ds
> that have this switch. The mediatek-ge PHY driver already disables EEE
> advertisement on the switch PHYs but my testing shows that it is somehow
> enabled afterwards. Disabling EEE advertisement before the PHY driver
> initialises keeps it off.
>=20
> With this change, EEE can now be enabled using ethtool.
>=20
> Fixes: 40b5d2f15c09 ("net: dsa: mt7530: Add support for EEE features")
> Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
> Signed-off-by: Ar=C4=B1n=C3=A7 =C3=9CNAL <arinc.unal@arinc9.com>
> ---
> Here's some information for the record. EEE could not be enabled on MT753=
1
> on most boards using ethtool before this. On MT7988 SoC switch, EEE is
> disabled by default but can be turned on normally using ethtool. EEE is
> enabled by default on MT7530 and there's no need to make changes on the D=
SA
> subdriver for it.
> ---
> Changes in v3:
> - Remove patch 2, it was revealed that it doesn't fix a bug.
> - Patch 1
>   - Use the internal EEE switch bit provided by SkyLake Huang (=E9=BB=83=
=E5=95=9F=E6=BE=A4). It
>     is a better method compared to unsetting the EEE_DIS bit of the trap =
as
>     the latter method causes unwanted behaviour on the LED connected to t=
he
>     pin that pertains to the EEE_DIS bit.

Since this leverages something relatively obscure, it would be great if
someone in the CC list could independently test it. Let's wait a bit
more.

Cheers,

Paolo