From: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
To: Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Peter Chen <hzpeterchen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>,
Greg Kroah-Hartman
<gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>,
Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
Alexander Shishkin
<alexander.shishkin-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>,
"linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Felipe Balbi <balbi-l0cyMroinI0@public.gmane.org>,
Alan Stern
<stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org>,
linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
Laura Abbott <lauraa-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
Subject: Re: [PATCH] USB: set device dma_mask without reference to global data
Date: Wed, 8 May 2013 16:07:54 +0200 [thread overview]
Message-ID: <201305081607.54839.arnd@arndb.de> (raw)
In-Reply-To: <518A582C.8070600-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
On Wednesday 08 May 2013, Rob Herring wrote:
> On 05/08/2013 02:11 AM, Matthijs Kooijman wrote:
> > https://lkml.org/lkml/2012/12/4/54
> >
> > And here's the previous attempt, to which Rob Herring refers in a reply.
> >
> > https://lists.ozlabs.org/pipermail/devicetree-discuss/2012-March/013180.html
>
> I believe most of the issues have been around supporting ARM LPAE
> systems. There is a much more simple approach to address this by using
> the dma_addr_t size to set the coherent_dma_mask which I have queued for
> 3.11:
>
> https://patchwork-mail1.kernel.org/patch/2495861/
Hmm, this approach seems wrong -- a lot of devices I expect cannot
actually do DMA to addresses beyond 4GB. A better default would
be to use a 32 bit mask for all devices and override the ones that
actually matter for performance and are known to be 64-bit DMA
capable.
Laura, you obviously tried this code on an LPAE-enabled system. Have
you had a look in the hardware manual which DMA masters in the
system are actually 64-bit capable?
Arnd
next prev parent reply other threads:[~2013-05-08 14:07 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-07 22:53 [PATCH] USB: set device dma_mask without reference to global data Stephen Warren
[not found] ` <1367967232-10128-1-git-send-email-swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
2013-05-07 23:04 ` Greg Kroah-Hartman
[not found] ` <20130507230445.GC9105-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2013-05-07 23:42 ` Arnd Bergmann
[not found] ` <201305080142.12025.arnd-r2nGTMty4D4@public.gmane.org>
2013-05-08 14:14 ` Alan Stern
[not found] ` <Pine.LNX.4.44L0.1305081011480.1450-100000-IYeN2dnnYyZXsRXLowluHWD2FQJk+8+b@public.gmane.org>
2013-05-08 15:10 ` Arnd Bergmann
2013-05-09 21:33 ` Russell King - ARM Linux
2013-05-08 5:11 ` Tony Prisk
2013-05-08 1:13 ` Peter Chen
2013-05-08 2:26 ` Stephen Warren
2013-05-08 2:54 ` Peter Chen
[not found] ` <CAL411-pY_i19otiE2pLux6eR_OFHhfhK=+6BF=H6wABDsGCP6Q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-05-08 7:11 ` Matthijs Kooijman
[not found] ` <20130508071137.GM25742-tJobPqrNDpleFRaWBN1JIYg6o0x57dKM8/qWW+O4k6E@public.gmane.org>
2013-05-08 7:28 ` Matthijs Kooijman
2013-05-08 13:50 ` Rob Herring
[not found] ` <518A582C.8070600-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2013-05-08 14:07 ` Arnd Bergmann [this message]
2013-05-08 7:24 ` Arnd Bergmann
[not found] ` <201305080924.44622.arnd-r2nGTMty4D4@public.gmane.org>
2013-05-09 21:39 ` Russell King - ARM Linux
2013-05-08 22:42 ` Stephen Warren
2013-05-09 21:36 ` Russell King - ARM Linux
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