linux-kernel - Re: [PATCH 3/3] dmaengine: Add Freescale i.MX SDMA support

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Date:	Wed, 18 Aug 2010 13:17:48 +0200
From:	Philippe Rétornaz <philippe.retornaz@...l.ch>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Sascha Hauer <s.hauer@...gutronix.de>,
	Baruch Siach <baruch@...s.co.il>,
	Linus Walleij <linus.ml.walleij@...il.com>,
	Dan Williams <dan.j.williams@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] dmaengine: Add Freescale i.MX SDMA support

Le mardi, 17 août 2010 08.47:34, Sascha Hauer a écrit :
> On Tue, Aug 17, 2010 at 07:36:12AM +0300, Baruch Siach wrote:
> > Hi Sascha,
> >
> > On Mon, Aug 16, 2010 at 04:15:40PM +0200, Sascha Hauer wrote:
> > > On Mon, Aug 16, 2010 at 02:21:06PM +0200, Linus Walleij wrote:
> > > > 2010/8/16 Sascha Hauer <s.hauer@...gutronix.de>:
> > > > > The SDMA engine is a scatter/gather DMA engine which is implemented
> > > > > as a seperate coprocessor. SDMA needs its own firmware which is
> > > > > requested using the standard request_firmware mechanism. The
> > > > > firmware has different entry points for each peripheral type, so
> > > > > drivers have to pass the peripheral type to the DMA engine which in
> > > > > turn picks the correct firmware entry point from a table contained
> > > > > in the firmware image itself.
> > > >
> > > > Quite fun, if the spec for the microcode is open this opens up
> > > > for dynamic firmware generation for specific DMA jobs does it
> > > > not?
> > >
> > > Unfortunately the specs are not open, so we are sticked to the binary
> > > microcode from Freescale. I'm pretty sure though that the SDMA engine
> > > could do at least a device_prep_dma_xor operation.
> >
> > Chapter 38 in the i.MX25 Reference Manual seems to include almost
> > everything there is to know about the SDMA. Isn't this enough for writing
> > custom SDMA microcodes?
> 
> Unfortunately not, the assembler is missing.
> 

I think the instruction list and encoding is available in the imx31 reference 
manual at section 40.19.

BTW, I tested the non-dmaengine version of your patch on imx31, works great !

Regards,

Philippe
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