linux-kernel - Re: [PATCH net 2/2] net: dsa: mv88e6xxx: Avoid EEPROM timeout without EEPROM on 88E6250-family switches

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Message-ID: <47350aa7-b4d0-49f0-98f5-4fc52c4f2c42@lunn.ch>
Date: Mon, 22 Apr 2024 15:31:04 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Matthias Schiffer <matthias.schiffer@...tq-group.com>
Cc: 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>,
	Fabio Estevam <festevam@...x.de>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux@...tq-group.com
Subject: Re: [PATCH net 2/2] net: dsa: mv88e6xxx: Avoid EEPROM timeout
 without EEPROM on 88E6250-family switches

On Thu, Apr 18, 2024 at 02:16:08PM +0200, Matthias Schiffer wrote:
> 88E6250-family switches have the quirk that the EEPROM Running flag can
> get stuck at 1 when no EEPROM is connected, causing
> mv88e6xxx_g2_eeprom_wait() to time out. We still want to wait for the
> EEPROM however, to avoid interrupting a transfer and leaving the EEPROM
> in an invalid state.
> 
> The condition to wait for recommended by the hardware spec is the EEInt
> flag, however this flag is cleared on read, so before the hardware reset,
> is may have been cleared already even though the EEPROM has been read
> successfully.
> 
> For this reason, we revive the mv88e6xxx_g1_wait_eeprom_done() function
> that was removed in commit 6ccf50d4d474
> ("net: dsa: mv88e6xxx: Avoid EEPROM timeout when EEPROM is absent") in a
> slightly refactored form, and introduce a new
> mv88e6xxx_g1_wait_eeprom_done_prereset() that additionally handles this
> case by triggering another EEPROM reload that can be waited on.
> 
> On other switch models without this quirk, mv88e6xxx_g2_eeprom_wait() is
> kept, as it avoids the additional reload.
> 
> Fixes: 6ccf50d4d474 ("net: dsa: mv88e6xxx: Avoid EEPROM timeout when EEPROM is absent")
> Signed-off-by: Matthias Schiffer <matthias.schiffer@...tq-group.com>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew