From: vkoul@infradead.org (Vinod Koul)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] dmaengine: add CSR SiRFprimaII DMAC driver
Date: Fri, 09 Sep 2011 21:55:08 +0530 [thread overview]
Message-ID: <1315585508.30522.3.camel@vkoul-mobl4> (raw)
In-Reply-To: <CAGsJ_4zaOwHvViuh=nKhvxw3irnE9mXaG_FAKLp_a__XpdXtSA@mail.gmail.com>
On Fri, 2011-09-09 at 10:52 +0800, Barry Song wrote:
> >
> > Actually, there is no real case for xlen > dma_width. this picture is
> > only explaining what will happen if we set xlen > dma_width.
> > when xlen > dma_width, for every line, dma will transfer only
> > dma_width. Then the extra data is wrapped around
> > to the next data line, it will corrupt the DMA transfer for
> > multiple-line 2-D DMA since the extra data will overlap with the real
> > next line.
> >
> > if we set ylen to 0, the DMA becomes 1D, the wrap-around of the extra
> > data has no issue nobody will overlap with it.
> >
>
> For example, if we set xlen = 7, dma_width =4, ylen > 0
> then dma will happen like:
> 0~6
> 4~10
> 8~14
> 12~18
> ....
Is there a real world use case of this??
>
> But for ylen=0, it has no issue. there is no next line to overlap with
> the extra data.
>
> in case we set xlen = 0, something funny will happen:
> i will copy the same memory again and again(ylen+1 times).
--
~Vinod Koul
Intel Corp.
next prev parent reply other threads:[~2011-09-09 16:25 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-07 5:41 [PATCH] dmaengine: add CSR SiRFprimaII DMAC driver Barry Song
2011-09-07 16:14 ` Koul, Vinod
2011-09-07 16:46 ` Barry Song
2011-09-07 18:09 ` Koul, Vinod
2011-09-08 2:18 ` Barry Song
[not found] ` <CAGsJ_4yeovNP=6CKTafbxrBTrYQ42B9yvAOM8gM_bYqD6mTnUw@mail.gmail.com>
2011-09-08 3:17 ` Jassi Brar
2011-09-08 5:25 ` Jassi Brar
2011-09-08 6:36 ` Barry Song
2011-09-08 7:49 ` Jassi Brar
2011-09-08 21:51 ` Vinod Koul
2011-09-09 2:35 ` Barry Song
2011-09-09 2:52 ` Barry Song
2011-09-09 16:25 ` Vinod Koul [this message]
2011-09-09 23:37 ` Barry Song
2011-09-11 15:59 ` Vinod Koul
2011-09-12 0:13 ` Barry Song
2011-09-08 21:46 ` Vinod Koul
2011-09-09 8:18 ` Barry Song
2011-09-09 16:21 ` Vinod Koul
2011-09-09 23:40 ` Barry Song
2011-09-10 7:33 ` Jassi Brar
2011-09-11 16:02 ` Vinod Koul
2011-09-12 6:33 ` Jassi Brar
2011-09-14 5:07 ` Vinod Koul
2011-09-14 6:46 ` Barry Song
2011-09-14 7:11 ` Jassi Brar
2011-09-14 9:49 ` Barry Song
2011-09-08 6:14 ` Barry Song
2011-09-08 6:37 ` Jassi Brar
2011-09-16 9:06 ` Barry Song
2011-09-07 19:27 ` Linus Walleij
2011-09-08 1:47 ` Barry Song
2011-09-08 14:52 ` Arnd Bergmann
2011-09-08 15:27 ` Barry Song
2011-09-08 16:19 ` Arnd Bergmann
2011-09-08 18:48 ` Linus Walleij
2011-09-08 20:11 ` Arnd Bergmann
2011-09-08 21:38 ` Vinod Koul
2011-09-11 21:27 ` Linus Walleij
2011-09-12 0:01 ` Barry Song
2011-09-14 4:54 ` Vinod Koul
2011-09-09 16:10 ` Vinod Koul
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