linux-kernel - Re: [PATCH v3] i2c: designware: fix __i2c_dw_disable() in case master is holding SCL low

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Message-ID: <2f215e0f-c2ed-4300-8b75-1949f17cdf1c@linux.intel.com>
Date:   Tue, 22 Aug 2023 13:14:45 +0300
From:   Jarkko Nikula <jarkko.nikula@...ux.intel.com>
To:     Yann Sionneau <ysionneau@...ray.eu>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Julian Vetter <jvetter@...rayinc.com>
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jonathan Borne <jborne@...ray.eu>
Subject: Re: [PATCH v3] i2c: designware: fix __i2c_dw_disable() in case master
 is holding SCL low

Hi

On 8/22/23 12:02, Yann Sionneau wrote:
> The DesignWare IP can be synthesized with the IC_EMPTYFIFO_HOLD_MASTER_EN
> parameter.
> In this case, when the TX FIFO gets empty and the last command didn't have
> the STOP bit (IC_DATA_CMD[9]), the controller will hold SCL low until
> a new command is pushed into the TX FIFO or the transfer is aborted.
> 
> When the controller is holding SCL low, it cannot be disabled.
> The transfer must first be aborted.
> Also, the bus recovery won't work because SCL is held low by the master.
> 
> Check if the master is holding SCL low in __i2c_dw_disable() before trying
> to disable the controller. If SCL is held low, an abort is initiated.
> When the abort is done, then proceed with disabling the controller.
> 
> This whole situation can happen for instance during SMBus read data block
> if the slave just responds with "byte count == 0".
> This puts the driver in an unrecoverable state, because the controller is
> holding SCL low and the current __i2c_dw_disable() procedure is not
> working. In this situation only a SoC reset can fix the i2c bus.
> 
Is this fixed already by the commit 69f035c480d7 ("i2c: designware: 
Handle invalid SMBus block data response length value")?

https://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git/commit/?h=i2c/for-next&id=69f035c480d76f12bf061148ccfd578e1099e5fc