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Subject: Re: [PATCH v2] i2c: bcm2835: Clear current buffer pointers and counts
 after a transfer
To:     Wolfram Sang <wsa@the-dreams.de>,
        Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Cc:     Florian Fainelli <f.fainelli@gmail.com>,
        Scott Branden <sbranden@broadcom.com>,
        Eben Upton <eben@raspberrypi.org>,
        Maxime Ripard <maxime.ripard@bootlin.com>,
        Ray Jui <rjui@broadcom.com>, linux-kernel@vger.kernel.org,
        Eric Anholt <eric@anholt.net>,
        bcm-kernel-feedback-list@broadcom.com, linux-i2c@vger.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-rpi-kernel@lists.infradead.org
References: <20181227154225.5492-1-paul.kocialkowski@bootlin.com>
 <20190205120905.GB1045@kunai>
From:   Stefan Wahren <stefan.wahren@i2se.com>
Message-ID: <3784fe11-bdc4-5751-13b4-f50bdeeee205@i2se.com>
Date:   Tue, 5 Feb 2019 15:14:36 +0100
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Am 05.02.19 um 13:09 schrieb Wolfram Sang:
> On Thu, Dec 27, 2018 at 04:42:25PM +0100, Paul Kocialkowski wrote:
>> The driver's interrupt handler checks whether a message is currently
>> being handled with the curr_msg pointer. When it is NULL, the interrupt
>> is considered to be unexpected. Similarly, the i2c_start_transfer
>> routine checks for the remaining number of messages to handle in
>> num_msgs.
>>
>> However, these values are never cleared and always keep the message and
>> number relevant to the latest transfer (which might be done already and
>> the underlying message memory might have been freed).
>>
>> When an unexpected interrupt hits with the DONE bit set, the isr will
>> then try to access the flags field of the curr_msg structure, leading
>> to a fatal page fault.
>>
>> The msg_buf and msg_buf_remaining fields are also never cleared at the
>> end of the transfer, which can lead to similar pitfalls.
>>
>> Fix these issues by introducing a cleanup function and always calling
>> it after a transfer is finished.
>>
>> Fixes: e2474541032d ("i2c: bcm2835: Fix hang for writing messages larger than 16 bytes")
>> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> Stefan, Florian, any comment about this patch?

Acked-by: Stefan Wahren <stefan.wahren@i2se.com>

Thanks