From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: pvvvarma@techmas.hcltech.com (Vasu Varma P V)
Cc: linux-kernel@vger.kernel.org (kernel Linux)
Subject: Re: DMA memory limitation?
Date: Thu, 5 Jul 2001 12:53:45 +0100 (BST) [thread overview]
Message-ID: <E15I7hZ-0002Q3-00@the-village.bc.nu> (raw)
In-Reply-To: <3B4453E6.F4342781@techmas.hcltech.com> from "Vasu Varma P V" at Jul 05, 2001 05:17:50 PM
> Is there any limitation on DMA memory we can allocate using
> kmalloc(size, GFP_DMA)? I am not able to acquire more than
> 14MB of the mem using this on my PCI SMP box with 256MB ram.
> I think there is restriction on ISA boards of 16MB.
Yes. GFP_DMA allocates memory below 16Mbytes for ISA devices and that is
a physical wiring issue. For PCI devices you can allocate a lot more using
the pci_alloc_* and pci_map_* interface to allocate memory for PCI in a
CPU independant manner. It'll also then look after cache coherency issues
for you
next prev parent reply other threads:[~2001-07-05 11:57 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-07-05 11:47 DMA memory limitation? Vasu Varma P V
2001-07-05 11:53 ` Alan Cox [this message]
2001-07-05 11:54 ` Arjan van de Ven
2001-07-05 12:37 ` Vasu Varma P V
2001-07-05 12:37 ` Richard B. Johnson
2001-07-05 17:07 ` Christophe Beaumont
2001-07-05 17:19 ` Richard B. Johnson
2001-07-06 8:59 ` Helge Hafting
2001-07-06 9:44 ` Steffen Persvold
2001-07-06 11:08 ` Alan Cox
2001-07-06 11:27 ` Jeff Garzik
2001-07-06 15:16 ` Steffen Persvold
2001-07-06 15:39 ` Jeff Garzik
2001-07-06 15:48 ` Alan Cox
2001-07-06 15:56 Matt_Domsch
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