linux-kernel - Re: [PATCH] i2c: aspeed: Add multi-master use case support

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Date:   Thu, 7 Feb 2019 11:48:51 -0800
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     Jae Hyun Yoo <jae.hyun.yoo@...ux.intel.com>
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>, linux-i2c@...r.kernel.org,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-aspeed@...ts.ozlabs.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        James Feist <james.feist@...ux.intel.com>,
        Vernon Mauery <vernon.mauery@...ux.intel.com>
Subject: Re: [PATCH] i2c: aspeed: Add multi-master use case support

On Wed, Jan 16, 2019 at 11:40 AM Jae Hyun Yoo
<jae.hyun.yoo@...ux.intel.com> 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 <jae.hyun.yoo@...ux.intel.com>
> ---
>  drivers/i2c/busses/i2c-aspeed.c | 118 +++++++++++++++++++++++++-------
>  1 file changed, 92 insertions(+), 26 deletions(-)
>

Reviewed-by: Brendan Higgins <brendanhiggins@...gle.com>