linux-kernel - Re: [PATCH] pasemi_dma: Driver for PA Semi PWRficient on-chip DMAengine

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Date:	Tue, 11 Mar 2008 10:04:11 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Olof Johansson <olof@...om.net>
Cc:	"Nelson, Shannon" <shannon.nelson@...el.com>,
	linux-kernel@...r.kernel.org, pasemi-linux@...abs.org,
	linuxppc-dev@...abs.org, hskinnemoen@...el.com
Subject: Re: [PATCH] pasemi_dma: Driver for PA Semi PWRficient on-chip
	DMAengine

On Thu, 2008-03-06 at 16:39 -0700, Olof Johansson wrote:
> pasemi_dma: Driver for PA Semi PWRficient on-chip DMA engine
>    
> First cut at a dma copy offload driver for PA Semi PWRficient. It uses the
> platform-specific functions to allocate channels, etc.
> 
> Signed-off-by: Olof Johansson <olof@...om.net>
> 
> 
> ---
> 
> This has some dependencies on other patches currently queued up in the
> powerpc git trees for 2.6.26. I'd appreciate reviews and acked-bys, but
> it might be easiest to just merge it up the powerpc path due to the
> dependencies.
> 
Apologies for not getting to this sooner.

I notice that the driver does not handle callbacks in its descriptor
cleanup path.  This could be ok if your intent is only to support the
net_dma style polled operations, but this will not work for the
raid-offload async_tx case.  I think the solution is for async_tx to
ignore channels without the DMA_INTERRUPT capability.

> +static void pasemi_dma_clean(struct pasemi_dma_chan *chan)
> +{
> +       int old, new, i;
> +       unsigned long flags;
> +       struct pasemi_dma_desc *desc;
> +       spin_lock_irqsave(&chan->desc_lock, flags);

Is spin_lock_bh() insufficient here?

...that's all that jumps out at the moment.

Regards,
Dan

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