linux-kernel - Re: [PATCH v7 01/10] ARM: davinci: move private EDMA API to arm/common

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Date:	Mon, 4 Feb 2013 19:02:16 +0200
From:	Felipe Balbi <balbi@...com>
To:	Sergei Shtylyov <sshtylyov@...sta.com>
CC:	<balbi@...com>, Russell King - ARM Linux <linux@....linux.org.uk>,
	Matt Porter <mporter@...com>,
	Linux DaVinci Kernel List 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	Chris Ball <cjb@...top.org>,
	"Cousson, Benoit" <b-cousson@...com>,
	Arnd Bergmann <arnd@...db.de>,
	Linux Documentation List <linux-doc@...r.kernel.org>,
	Tony Lindgren <tony@...mide.com>,
	Devicetree Discuss <devicetree-discuss@...ts.ozlabs.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Linux MMC List <linux-mmc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Vinod Koul <vinod.koul@...el.com>,
	Rob Landley <rob@...dley.net>, Dan Williams <djbw@...com>,
	Linux SPI Devel List 
	<spi-devel-general@...ts.sourceforge.net>,
	Linux OMAP List <linux-omap@...r.kernel.org>,
	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v7 01/10] ARM: davinci: move private EDMA API to
 arm/common

Hi,

On Mon, Feb 04, 2013 at 08:54:17PM +0300, Sergei Shtylyov wrote:
> > On Mon, Feb 04, 2013 at 08:36:38PM +0300, Sergei Shtylyov wrote:
> >>> opted out of it. From the top of my head we have CPPI 3.x, CPPI 4.1,
> >>> Inventra DMA, OMAP sDMA and ux500 DMA engines supported by the driver.
> 
> >>> Granted, CPPI 4.1 makes some assumptions about the fact that it's
> >>> handling USB tranfers,
> 
> >>    What CPPI 4.1 code makes this assumptions? MUSB DMA driver? Then it's just
> 
> > HW makes the asumptions
> 
>    Not true at all. There is a separate set of registers (at offset 0) which
> copes with USB specifics, but CPPI 4.1 itself doesn't know about USB anything.

CPPI 4.1 was made for USB transfers.

> It's just the way the driver was written that it used both sets of registers but
> this needs to be changed into more abstacted accesses to the USB-specific part,
> to cope with it being different on different platfroms, like AM35x. The driver
> as it was last posted, just needs rework now.

are you saying you will do the work ?

> >>    Don't know, I was quite content with the abstraction when writing CPPI 4.1
> >> driver for MUSB...
> 
> > look closer. The whole:
> 
> > if (is_cppi())
> > 	foo();
> > else if (is_inventra())
> > 	bar();
> > else if (is_omap_sdma())
> > 	baz();
> 
> > is bogus.
> 
>    That part -- yes. There were attempt to get rid of this, but without changing
> the DMA API. It was left halfway done after my only critical comment, IIRC. Will
> we ever see the continuation of this effort?

patches are welcome

-- 
balbi

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