linux-kernel - Re: [PATCH] dmaengine: pxa: handle bus errors

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Message-ID: <20160426033436.GC2274@localhost>
Date:	Tue, 26 Apr 2016 09:04:36 +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: handle bus errors

On Mon, Mar 28, 2016 at 11:32:24PM +0200, Robert Jarzmik wrote:
> In the current state, upon bus error the driver will spin endlessly,
> relaunching the last tx, which will fail again and again :
>  - a bus error happens
>  - pxad_chan_handler() is called
>  - as PXA_DCSR_STOPSTATE is true, the last non-terminated transaction is
>    lauched, which is the one triggering the bus error, as it didn't
>    terminate
>  - moreover, the STOP interrupt fires a new, as the STOPIRQEN is still
>    active
> 
> Break this logic by stopping the automatic relaunch of a dma channel
> upon a bus error, even if there are still pending issued requests on it.
> 
> As dma_cookie_status() seems unable to return DMA_ERROR in its current
> form, ie. there seems no way to mark a DMA_ERROR on a per-async-tx
> basis, it is chosen in this patch to remember on the channel which
> transaction failed, and report it in pxad_tx_status().
> 
> It's a bit misleading because if T1, T2, T3 and T4 were queued, and T1
> was completed while T2 causes a bus error, the status of T3 and T4 will
> be reported as DMA_IN_PROGRESS, while the channel is actually stopped.

Applied, thanks

-- 
~Vinod