linux-kernel - Re: [PATCHv2] DMAEngine: Let dmac drivers to set chan

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Date:	Fri, 29 Jul 2011 17:24:09 +0530
From:	"Koul, Vinod" <vinod.koul@...el.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Jaswinder Singh <jaswinder.singh@...aro.org>,
	Russell King <rmk@....linux.org.uk>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linus.walleij@...ricsson.com,
	per.friden@...ricsson.com, wei.zhang@...escale.com,
	ebony.zhu@...escale.com, iws@...o.caltech.edu,
	s.hauer@...gutronix.de, maciej.sosnowski@...el.com,
	saeed@...vell.com, shawn.guo@...escale.com, yur@...raft.com,
	agust@...x.de, iwamatsu.nobuhiro@...esas.com,
	per.forlin@...ricsson.com, jonas.aberg@...ricsson.com,
	anemo@....ocn.ne.jp
Subject: Re: [PATCHv2] DMAEngine: Let dmac drivers to set chan_id

On Fri, 2011-07-29 at 00:27 +0200, Linus Walleij wrote:
> On Thu, Jul 28, 2011 at 12:44 PM, Jaswinder Singh
> <jaswinder.singh@...aro.org> wrote:
> 
> > {
> > So far, I haven't assumed the capability of a DMAC to switch, say,
> > the RequestSignal_7 from MMC to UART at _runtime_
> > If you think such dmacs and platforms exist, please let me know.
> > I will update the proposal.
> > }
> 
> Such DMACs exist, in the ARM Versatile and RealView boards...
> Check drivers/dma/amba-pl08x.c, notice callback functions named
> int (*get_signal)(struct pl08x_dma_chan *);
> void (*put_signal)(struct pl08x_dma_chan *);
> from <linux/amba/pl08x.h>
> 
> These implement optional runtime muxing of the request signals,
> and it is through these two callbacks because there is a mux
> which is external to the pl08x itself that is used, and the muxing
> is machine-specific and implemented in the platform. I have been
> working on patches using it like the below (still being worked on).
> 
Yes, even in intel_mid_dmac we have such a mux so that DMAC channels can
transfer to any of the h/w interfaces. This configuration can be passed
by client (which instance) and dmac configures it :)
So all channels for a controller can do transfers to any of the
peripherals...

-- 
~Vinod

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