linux-kernel - Re: [PATCH v2] dma: mmp_pdma: fix a memory alloc error

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Message-ID: <20130819091730.GB5810@intel.com>
Date:	Mon, 19 Aug 2013 14:47:30 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Xiang Wang <wangxfdu@...il.com>
Cc:	Dan Williams <djbw@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	cxie4@...vell.com, Xiang Wang <wangx@...vell.com>
Subject: Re: [PATCH v2] dma: mmp_pdma: fix a memory alloc error

On Thu, Aug 01, 2013 at 10:27:47AM +0800, Xiang Wang wrote:
> 2013/7/29 Vinod Koul <vinod.koul@...el.com>:
> > On Thu, Jul 25, 2013 at 10:22:50AM +0800, Xiang Wang wrote:
> >
> > Btw its generally a good idea to remove the parts not required for further
> > discussion
> >
> >> Would you please explain a little more about why we should use
> >> GFP_NOWAIT here? This memory is not dedicated for DMA controller. Do
> >> we have special reasons to use GFP_NOWAIT? Thanks!
> > There are few reasons
> > - the dma requests can be triggered from atomic context
> > - so for above you can argue to use the GFP_ATOMIC and the guideline for dma
> >   drivers [1] was discussed briefly
> >
> > ~Vinod
> > [1]: http://lkml.indiana.edu/hypermail/linux/kernel/0911.1/02316.html
> >
> > --
> Hi, Vinod
> Thanks for your explanation. But want to double confirm with you that
> the memory alloc in my patch is in probe function, still need to use
> GFP_NOWAIT? Thanks!
Yes I would recommend it

~Vinod
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