linux-kernel - Re: [PATCH v0 1/2] DMA: fsldma: Disable DMA_INTERRUPT when Async

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Date:	Thu, 15 Oct 2009 18:25:14 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Vishnu Suresh <Vishnu@...escale.com>
Cc:	linuxppc-dev@...abs.org, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
	herbert@...dor.apana.org.au, Li Yang <leoli@...escale.com>,
	Timur Tabi <timur@...escale.com>
Subject: Re: [PATCH v0 1/2] DMA: fsldma: Disable DMA_INTERRUPT when Async_tx 
	enabled

[ added Leo and Timur to the Cc ]

On Wed, Oct 14, 2009 at 11:41 PM, Vishnu Suresh <Vishnu@...escale.com> wrote:
> This patch disables the use of DMA_INTERRUPT capability with Async_tx
>
> The fsldma produces a null transfer with DMA_INTERRUPT
> capability when used with Async_tx. When RAID devices queue
> a transaction via Async_tx, this  results in a hang.
>
> Signed-off-by: Vishnu Suresh <Vishnu@...escale.com>
> ---
>  drivers/dma/fsldma.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c
> index 296f9e7..66d9b39 100644
> --- a/drivers/dma/fsldma.c
> +++ b/drivers/dma/fsldma.c
> @@ -1200,7 +1200,13 @@ static int __devinit of_fsl_dma_probe(struct of_device *dev,
>                                                - fdev->reg.start + 1);
>
>        dma_cap_set(DMA_MEMCPY, fdev->common.cap_mask);
> +#ifndef CONFIG_ASYNC_CORE
> +       /*
> +        * The DMA_INTERRUPT async_tx is a NULL transfer, which will
> +        * triger a PE interrupt.
> +        */
>        dma_cap_set(DMA_INTERRUPT, fdev->common.cap_mask);
> +#endif
>        dma_cap_set(DMA_SLAVE, fdev->common.cap_mask);
>        fdev->common.device_alloc_chan_resources = fsl_dma_alloc_chan_resources;
>        fdev->common.device_free_chan_resources = fsl_dma_free_chan_resources;

You are basically saying that fsl_dma_prep_interrupt() is buggy.  Can
that routine be fixed rather than this piecemeal solution?  If it
cannot be fixed (i.e. hardware issue) then fsl_dma_prep_interrupt()
should just be disabled/deleted altogether.

--
Dan
--
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