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Message-ID: <3f3acf78-f4be-47ff-a976-b60b327c2c28@lunn.ch>
Date: Wed, 27 Sep 2023 14:12:39 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Fabio Estevam <festevam@...il.com>
Cc: kuba@...nel.org, f.fainelli@...il.com, olteanv@...il.com,
davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
l00g33k@...il.com, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, Fabio Estevam <festevam@...x.de>,
Florian Fainelli <florian.fainelli@...adcom.com>
Subject: Re: [PATCH v3 net] net: dsa: mv88e6xxx: Avoid EEPROM timeout when
EEPROM is absent
On Fri, Sep 22, 2023 at 09:47:41AM -0300, Fabio Estevam wrote:
> From: Fabio Estevam <festevam@...x.de>
>
> Since commit 23d775f12dcd ("net: dsa: mv88e6xxx: Wait for EEPROM done
> before HW reset") the following error is seen on a imx8mn board with
> a 88E6320 switch:
>
> mv88e6085 30be0000.ethernet-1:00: Timeout waiting for EEPROM done
>
> This board does not have an EEPROM attached to the switch though.
>
> This problem is well explained by Andrew Lunn:
>
> "If there is an EEPROM, and the EEPROM contains a lot of data, it could
> be that when we perform a hardware reset towards the end of probe, it
> interrupts an I2C bus transaction, leaving the I2C bus in a bad state,
> and future reads of the EEPROM do not work.
>
> The work around for this was to poll the EEInt status and wait for it
> to go true before performing the hardware reset.
>
> However, we have discovered that for some boards which do not have an
> EEPROM, EEInt never indicates complete. As a result,
> mv88e6xxx_g1_wait_eeprom_done() spins for a second and then prints a
> warning.
>
> We probably need a different solution than calling
> mv88e6xxx_g1_wait_eeprom_done(). The datasheet for 6352 documents the
> EEPROM Command register:
>
> bit 15 is:
>
> EEPROM Unit Busy. This bit must be set to a one to start an EEPROM
> operation (see EEOp below). Only one EEPROM operation can be
> executing at one time so this bit must be zero before setting it to
> a one. When the requested EEPROM operation completes this bit will
> automatically be cleared to a zero. The transition of this bit from
> a one to a zero can be used to generate an interrupt (the EEInt in
> Global 1, offset 0x00).
>
> and more interesting is bit 11:
>
> Register Loader Running. This bit is set to one whenever the
> register loader is busy executing instructions contained in the
> EEPROM."
>
> Change to using mv88e6xxx_g2_eeprom_wait() to fix the timeout error
> when the EEPROM chip is not present.
>
> Fixes: 23d775f12dcd ("net: dsa: mv88e6xxx: Wait for EEPROM done before HW reset")
> Suggested-by: Andrew Lunn <andrew@...n.ch>
> Signed-off-by: Fabio Estevam <festevam@...x.de>
> Reviewed-by: Florian Fainelli <florian.fainelli@...adcom.com>
Reviewed-by: Andrew Lunn <andrew@...n.ch>
Andrew
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