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From: Wolfram Sang <>
To: Jae Hyun Yoo <>
	James Feist <>,
	Andrew Jeffery <>,
	Benjamin Herrenschmidt <>,,
	Brendan Higgins <>,,
	Jarkko Nikula <>,
	Joel Stanley <>,
	Vernon Mauery <>,,
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> (raw)
In-Reply-To: <>

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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.
> 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.
> Signed-off-by: Jae Hyun Yoo <>

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:

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

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linux-arm-kernel mailing list

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Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-16 19:39 Jae Hyun Yoo
2019-01-31 18:20 ` Jae Hyun Yoo
2019-02-07 19:48 ` Brendan Higgins
2019-02-08 21:48 ` Wolfram Sang [this message]
2019-02-11 18:09   ` Jae Hyun Yoo
2019-02-11 18:16     ` Wolfram Sang
2019-02-11 18:29       ` Jae Hyun Yoo

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