linux-kernel - Re: [PATCH v2 1/9] arm: mvebu: Limit the DMA zone when LPAE is selected

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Date:	Fri, 05 Apr 2013 22:59:59 +0200
From:	Gregory CLEMENT <gregory.clement@...e-electrons.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Jason Cooper <jason@...edaemon.net>, Andrew Lunn <andrew@...n.ch>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	linux-arm-kernel@...ts.infradead.org,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	Olof Johansson <olof@...om.net>,
	Nicolas Pitre <nico@...xnic.net>,
	Lior Amsalem <alior@...vell.com>,
	Maen Suleiman <maen@...vell.com>,
	Tawfik Bayouk <tawfik@...vell.com>,
	Shadi Ammouri <shadi@...vell.com>,
	Eran Ben-Avi <benavi@...vell.com>,
	Yehuda Yitschak <yehuday@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Ike Pan <ike.pan@...onical.com>,
	Chris Van Hoof <vanhoof@...onical.com>,
	Dan Frazier <dann.frazier@...onical.com>,
	Leif Lindholm <leif.lindholm@....com>,
	Jon Masters <jcm@...hat.com>,
	David Marlin <dmarlin@...hat.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH v2 1/9] arm: mvebu: Limit the DMA zone when LPAE is selected

On 04/05/2013 10:41 PM, Arnd Bergmann wrote:
> On Friday 05 April 2013, Gregory CLEMENT wrote:
>> When LPAE is activated on Armada XP, all registers and IOs are still
>> 32bit, the 40bit extension is on the CPU to DRAM path (windows) only.
>> That means that all the DMA transfer are restricted to the low 32 bits
>> address space. This is limitation is achieved by selecting ZONE_DMA.
>>
>> Signed-off-by: Gregory CLEMENT <gregory.clement@...e-electrons.com>
> 
> 
> Shouldn't that be ZONE_DMA32?
> 

Well common code for ARM don't manage the ZONE_DMA32. Whereas with
ZONE_DMA, setup_dma_zone() in arch/arm/mm/init.c does exactly what
I want: setting arm_dma_limit to 0xffffffff.

ZONE_DMA32 is used on arm64 however.

> 	Arnd
> 


-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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