linux-kernel - Re: [PATCH] i2c: aspeed: Acknowledge most interrupts early in interrupt handler

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Message-ID: <20180924214523.GA18592@kunai>
Date:   Mon, 24 Sep 2018 23:45:23 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Brendan Higgins <brendanhiggins@...gle.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>, linux-i2c@...r.kernel.org,
        openbmc@...ts.ozlabs.org, linux-aspeed@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org,
        Cédric Le Goater <clg@...d.org>,
        Jae Hyun Yoo <jae.hyun.yoo@...ux.intel.com>
Subject: Re: [PATCH] i2c: aspeed: Acknowledge most interrupts early in
 interrupt handler

On Thu, Sep 13, 2018 at 08:30:10PM -0700, Guenter Roeck wrote:
> Commit 3e9efc3299dd ("i2c: aspeed: Handle master/slave combined irq events
> properly") moved interrupt acknowledgment to the end of the interrupt
> handler. In part this was done because the AST2500 datasheet says:
> 
>  I2CD10 Interrupt Status Register
>    bit 2 Receive Done Interrupt status
>          S/W needs to clear this status bit to allow next data receiving.
> 
> Acknowledging Receive Done before receive data was handled resulted in
> receive errors on high speed I2C busses.
> 
> However, interrupt acknowledgment was not only moved to the end of the
> interrupt handler for Receive Done Interrupt status, but for all interrupt
> status bits. This could result in race conditions if a second interrupt was
> received during interrupt handling and not handled but still acknowledged
> at the end of the interrupt handler.
> 
> Acknowledge only "Receive Done Interrupt status" late in the interrupt
> handler to solve the problem.
> 
> Fixes: 3e9efc3299dd ("i2c: aspeed: Handle master/slave combined irq events properly")
> Cc: Jae Hyun Yoo <jae.hyun.yoo@...ux.intel.com>
> Cc: Joel Stanley <joel@....id.au>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>

Applied to for-next, thanks!


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