From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wolfram Sang <wsa@the-dreams.de>
Subject: Re: [PATCH] i2c: aspeed: Add multi-master use case support
Date: Fri, 8 Feb 2019 22:48:49 +0100
Message-ID: <20190208214849.GH12451@kunai>
References: <20190116193958.6049-1-jae.hyun.yoo@linux.intel.com>
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In-Reply-To: <20190116193958.6049-1-jae.hyun.yoo@linux.intel.com>
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To: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Cc: Brendan Higgins <brendanhiggins@google.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Joel Stanley <joel@jms.id.au>, Andrew Jeffery <andrew@aj.id.au>, linux-i2c@vger.kernel.org, openbmc@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org, Jarkko Nikula <jarkko.nikula@linux.intel.com>, James Feist <james.feist@linux.intel.com>, Vernon Mauery <vernon.mauery@linux.intel.com>
List-Id: linux-i2c@vger.kernel.org


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On Wed, Jan 16, 2019 at 11:39:58AM -0800, Jae Hyun Yoo wrote:
> In multi-master environment, this driver's master cannot know
> exactly when a peer master sends data to this driver's slave so
> cases can be happened that this master tries sending data through
> the master_xfer function but slave data from a peer master is still
> being processed or slave xfer is started by a peer immediately
> after it queues a master command. To support multi-master use cases
> properly, this H/W provides arbitration in physical level and it
> provides priority based command handling too to avoid conflicts in
> multi-master environment, means that if a master and a slave events
> happen at the same time, H/W will handle a higher priority event
> first and a pending event will be handled when bus comes back to
> the idle state.
>=20
> To support this H/W feature properly, this patch adds the 'pending'
> state of master and its handling code so that the pending master
> xfer can be continued after slave operation properly.
>=20
> Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>

Hmmm, the #ifdeffery quite increases with this patch. Maybe it is easier
to select I2C_SLAVE in Kconfig? I'll let you decide.

My code checkers found this:

    CPPCHECK
drivers/i2c/busses/i2c-aspeed.c:694:10: warning: Variable 'ret' is assigned=
 a value that is never used. [unreadVariable]


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