linux-kernel - RE: [RFC PATCH v3 05/16] ARM: edma: add AM33XX crossbar event support

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Date:	Fri, 26 Oct 2012 12:53:45 +0000
From:	"Hebbar, Gururaja" <gururaja.hebbar@...com>
To:	"Porter, Matt" <mporter@...com>
CC:	Linux DaVinci Kernel List 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	Arnd Bergmann <arnd@...db.de>,
	Linux Documentation List <linux-doc@...r.kernel.org>,
	Devicetree Discuss <devicetree-discuss@...ts.ozlabs.org>,
	Linux MMC List <linux-mmc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Rob Herring <rob.herring@...xeda.com>,
	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>,
	Tony Lindgren <tony@...mide.com>,
	"Nori, Sekhar" <nsekhar@...com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	"Cousson, Benoit" <b-cousson@...com>,
	Russell King <linux@....linux.org.uk>,
	Vinod Koul <vinod.koul@...el.com>,
	Rob Landley <rob@...dley.net>, Chris Ball <cjb@...top.org>
Subject: RE: [RFC PATCH v3 05/16] ARM: edma: add AM33XX crossbar event
 support

On Thu, Oct 18, 2012 at 18:56:44, Porter, Matt wrote:
> Adds support for the per-EDMA channel event mux. This is required
> for any peripherals using DMA crossbar mapped events.
> 
> Signed-off-by: Matt Porter <mporter@...com>
> ---
>  arch/arm/common/edma.c             |   63 +++++++++++++++++++++++++++++++++++-
>  include/linux/platform_data/edma.h |    1 +
>  2 files changed, 63 insertions(+), 1 deletion(-)
> 

..snip..
..snip..

> +
> +	for (i = 0; xbar_chans[i][0] != -1; i++) {
> +		shift = (xbar_chans[i][1] % 4) * 8;
> +		offset = xbar_chans[i][1] >> 2;
> +		offset <<= 2;
> +		mux = __raw_readl((void *)((u32)xbar + offset));
> +		mux &= (~(0xff << shift));
> +		mux |= (xbar_chans[i][0] << shift);
> +		__raw_writel(mux, (void *)((u32)xbar + offset));

This method of calculating Xbar Channel offset has a bug that
the code breaks with unaligned access trap error when requested 
channel to be mapped is odd.

This was fixed in Arago tree [1]. Kindly verify


> +	}
> +
> +	pdata->xbar_chans = xbar_chans;
> +
> +	return 0;
> +}
> +

..snip..
..snip..

[1]
http://arago-project.org/git/projects/?p=linux-am33x.git;a=commitdiff;
h=c08d3cb557adf71c79aeefb38888395455824e83

Regards, 
Gururaja
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