linux-kernel - Re: [PATCH v2] net: phy: disable eee due to errata on various KSZ switches

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Message-ID: <013420e6-12c7-45df-986c-22b3e2c1f610@lunn.ch>
Date: Mon, 7 Oct 2024 19:17:14 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Tim Harvey <tharvey@...eworks.com>
Cc: Woojung Huh <woojung.huh@...rochip.com>, UNGLinuxDriver@...rochip.com,
	Florian Fainelli <f.fainelli@...il.com>,
	Vladimir Oltean <olteanv@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: phy: disable eee due to errata on various KSZ
 switches

On Mon, Oct 07, 2024 at 10:10:32AM -0700, Tim Harvey wrote:
> The well-known errata regarding EEE not being functional on various KSZ
> switches has been refactored a few times. Recently the refactoring has
> excluded several switches that the errata should also apply to.
> 
> Disable EEE for additional switches with this errata.
> 
> The original workaround for the errata was applied with a register
> write to manually disable the EEE feature in MMD 7:60 which was being
> applied for KSZ9477/KSZ9897/KSZ9567 switch ID's.
> 
> Then came commit ("26dd2974c5b5 net: phy: micrel: Move KSZ9477 errata
> fixes to PHY driver") and commit ("6068e6d7ba50 net: dsa: microchip:
> remove KSZ9477 PHY errata handling") which moved the errata from the
> switch driver to the PHY driver but only for PHY_ID_KSZ9477 (PHY ID)
> however that PHY code was dead code because an entry was never added
> for PHY_ID_KSZ9477 via MODULE_DEVICE_TABLE.
> 
> This was apparently realized much later and commit ("54a4e5c16382 net:
> phy: micrel: add Microchip KSZ 9477 to the device table") added the
> PHY_ID_KSZ9477 to the PHY driver but as the errata was only being
> applied to PHY_ID_KSZ9477 it's not completely clear what switches
> that relates to.
> 
> Later commit ("6149db4997f5 net: phy: micrel: fix KSZ9477 PHY issues
> after suspend/resume") breaks this again for all but KSZ9897 by only
> applying the errata for that PHY ID.
> 
> The most recent time this was affected was with commit ("08c6d8bae48c
> net: phy: Provide Module 4 KSZ9477 errata (DS80000754C)") which
> removes the blatant register write to MMD 7:60 and replaces it by
> setting phydev->eee_broken_modes = -1 so that the generic phy-c45 code
> disables EEE but this is only done for the KSZ9477_CHIP_ID (Switch ID).
> 
> Signed-off-by: Tim Harvey <tharvey@...eworks.com>
> ---
> v2: added fixes tag and history of issue

You did?

Also, you need to set the subject line to net.

https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html

       Andrew