linux-kernel - Re: [PATCH] dmaengine: pxa_dma: fix hotchain corner case

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Message-ID: <20160819063224.GU9681@localhost>
Date:   Fri, 19 Aug 2016 12:02:24 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Robert Jarzmik <robert.jarzmik@...e.fr>
Cc:     Daniel Mack <daniel@...que.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        linux-arm-kernel@...ts.infradead.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: pxa_dma: fix hotchain corner case

On Sun, Aug 07, 2016 at 09:01:48PM +0200, Robert Jarzmik wrote:
> In the case where a descriptor is chained on a running channel, and as
> explained in the comment in the code 10 lines above, the success of the
> chaining is ensured either if :
>  - the DMA is still running
>  - or if the chained transfer is completed
> 
> Unfortunately the transfer completness test was done on the descriptor
> to which the transfer was chained, and not the transfer being chained at
> the end, ie. hot-chained.
> 
> This corner case is extremely hard to trigger, as usually the DMA chain
> is still running, and the first case takes care of returning success of
> the hot-chaining. It was seen by hot-chaining several "small transfers"
> to a running "big transfer", not in a real-life usecase but by testing
> the robustness of the driver.

Applied, thanks

-- 
~Vinod