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From: Russell King - ARM Linux <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>
To: Enrico Scholz
	<enrico.scholz-wttK6gPy29v+Hn7q9Vec/7NAH6kLmebB@public.gmane.org>
Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
Subject: Re: [i2c-mxs] Broken DMA operations from within a module
Date: Wed, 13 Feb 2013 12:14:50 +0000	[thread overview]
Message-ID: <20130213121450.GA17833@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <lyehgkift9.fsf-ZECJmDZ6y6nH/BybaBJVFuwNITXz66n+UvKB7fB21xCELgA04lAiVw@public.gmane.org>

On Wed, Feb 13, 2013 at 01:00:50PM +0100, Enrico Scholz wrote:
> E.g. when doing something like
> 
> 	struct i2c_msg xfer = {
>                .buf = "something",
>                ...
>         };
> 
>         ret = i2c_transfer(client->adapter, &xfer, 1);
> 
> random data will be sent because buf is not DMA mapable ("something" is
> located in the .strtab section within module memory). MXS has a memory
> layout like

DMA buffers must be located in lowmem *always*.  This means placing them
in the .data segment does not work.  USB has been through this already
and it's well known there...

  parent reply	other threads:[~2013-02-13 12:14 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-02-13 12:00 [i2c-mxs] Broken DMA operations from within a module Enrico Scholz
     [not found] ` <lyehgkift9.fsf-ZECJmDZ6y6nH/BybaBJVFuwNITXz66n+UvKB7fB21xCELgA04lAiVw@public.gmane.org>
2013-02-13 12:14   ` Russell King - ARM Linux [this message]
     [not found]     ` <20130213121450.GA17833-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org>
2013-02-13 12:28       ` Enrico Scholz

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