From: Sascha Hauer <s.hauer@pengutronix.de>
To: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH] i2c/pca954x: Initialize the mux to disconnected state
Date: Mon, 9 Sep 2019 10:48:30 +0200 [thread overview]
Message-ID: <20190909084830.5fxgs7oihsecquhm@pengutronix.de> (raw)
In-Reply-To: <20190908000314.27078-1-andrew.smirnov@gmail.com>
On Sat, Sep 07, 2019 at 05:03:14PM -0700, Andrey Smirnov wrote:
> Port of a Linux kernel commit cd823db8b1161ef0d756514d280715a576d65cc3
>
> pca954x power-on default is channel 0 connected. If multiple pca954x
> muxes are connected to the same physical I2C bus, the parent bus will
> see channel 0 devices behind both muxes by default. This is bad.
>
> Scenario:
> -- pca954x @ 0x70 -- ch 0 (I2C-bus-101) -- EEPROM @ 0x50
> |
> I2C-bus-1 ---
> |
> -- pca954x @ 0x71 -- ch 0 (I2C-bus-111) -- EEPROM @ 0x50
>
> 1. Load I2C bus driver: creates I2C-bus-1
> 2. Load pca954x driver: creates virtual I2C-bus-101 and I2C-bus-111
> 3. Load eeprom driver
> 4. Try to read EEPROM @ 0x50 on I2C-bus-101. The transaction will also bleed
> onto I2C-bus-111 because pca954x @ 0x71 channel 0 is connected by default.
>
> Fix: Initialize pca954x to disconnected state in pca954x_probe()
>
> Signed-off-by: Petri Gynther <pgynther@google.com>
> Signed-off-by: Jean Delvare <khali@linux-fr.org>
> Cc: stable@kernel.org
>
> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> ---
> drivers/i2c/muxes/i2c-mux-pca954x.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
Applied with whitespace cleanup, thanks
Sascha
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prev parent reply other threads:[~2019-09-09 8:48 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-08 0:03 Andrey Smirnov
2019-09-09 8:48 ` Sascha Hauer [this message]
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