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From: Russell King - ARM Linux <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>
To: Laura Abbott <lauraa-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
Cc: Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>,
	"devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org"
	<devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org>,
	"linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org"
	<linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>
Subject: Re: [PATCH] of: Set the DMA mask to 64 bits on ARM LPAE systems
Date: Thu, 25 Apr 2013 18:58:19 +0100	[thread overview]
Message-ID: <20130425175819.GF14496@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <51796365.5030405-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>

On Thu, Apr 25, 2013 at 10:09:57AM -0700, Laura Abbott wrote:
> I thought about this as well but in arch/arm/mm/mm.h:
>
> #ifdef CONFIG_ZONE_DMA
> extern phys_addr_t arm_dma_limit;
> #else
> #define arm_dma_limit ((phys_addr_t)~0)
> #endif
>
> arm_dma_limit is explicitly cast to phys_addr_t, which means that  
> arm_dma_limit will be always be sizeof(phys_addr_t) regardless of  
> sizeof(dma_addr_t).

This is the size of the DMA zone, which controls the _minimum_ DMA mask
that can be used in the system.  DMA masks must always be greater than
this limit.

  parent reply	other threads:[~2013-04-25 17:58 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-24  0:50 [PATCH] of: Set the DMA mask to 64 bits on ARM LPAE systems Laura Abbott
2013-04-25 13:33 ` Catalin Marinas
2013-04-25 17:09   ` Laura Abbott
     [not found]     ` <51796365.5030405-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2013-04-25 17:58       ` Russell King - ARM Linux [this message]
2013-04-26 10:00     ` Catalin Marinas
     [not found]       ` <20130426100001.GB5007-bi+AKbBUZKZEOHzHbR49IE74JuZQtDDkQQ4Iyu8u01E@public.gmane.org>
2013-04-26 16:58         ` Laura Abbott

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