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

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Date:	Tue, 17 Aug 2010 08:47:34 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Baruch Siach <baruch@...s.co.il>
Cc:	Linus Walleij <linus.ml.walleij@...il.com>,
	Dan Williams <dan.j.williams@...el.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/3] dmaengine: Add Freescale i.MX SDMA support

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.

Sascha

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