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Message-ID: <20171128150142.dpxg5xdkza5y6qqg@rob-hp-laptop>
Date: Tue, 28 Nov 2017 09:01:42 -0600
From: Rob Herring <robh@...nel.org>
To: Peter Rosin <peda@...ntia.se>
Cc: linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
Nicolas Ferre <nicolas.ferre@...rochip.com>,
Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
Russell King <linux@...linux.org.uk>,
Guenter Roeck <linux@...ck-us.net>,
Jean Delvare <jdelvare@...e.com>,
Ludovic Desroches <ludovic.desroches@...rochip.com>,
devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v2 1/2] hwmon: (jc42) optionally try to disable the SMBUS
timeout
On Mon, Nov 27, 2017 at 05:31:00PM +0100, Peter Rosin wrote:
> With a nxp,se97 chip on an atmel sama5d31 board, the I2C adapter driver
> is not always capable of avoiding the 25-35 ms timeout as specified by
> the SMBUS protocol. This may cause silent corruption of the last bit of
> any transfer, e.g. a one is read instead of a zero if the sensor chip
> times out. This also affects the eeprom half of the nxp-se97 chip, where
> this silent corruption was originally noticed. Other I2C adapters probably
> suffer similar issues, e.g. bit-banging comes to mind as risky...
>
> The SMBUS register in the nxp chip is not a standard Jedec register, but
> it is not special to the nxp chips either, at least the atmel chips
> have the same mechanism. Therefore, do not special case this on the
> manufacturer, it is opt-in via the device property anyway.
>
> Signed-off-by: Peter Rosin <peda@...ntia.se>
> ---
> Documentation/devicetree/bindings/hwmon/jc42.txt | 4 ++++
Acked-by: Rob Herring <robh@...nel.org>
> drivers/hwmon/jc42.c | 21 +++++++++++++++++++++
> 2 files changed, 25 insertions(+)
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