Date: Sun, 16 Dec 2007 20:16:43 +0000
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Oliver Joa <oliver@j-o-a.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: How to Switch DMA off for only one Harddisk at Kernelboot
Message-ID: <20071216201643.396fa8d7@the-village.bc.nu>
In-Reply-To: <4765690C.6010605@j-o-a.de>
References: <4765690C.6010605@j-o-a.de>
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On Sun, 16 Dec 2007 19:06:04 +0100
Oliver Joa <oliver@j-o-a.de> wrote:

> Hi,
> 
> how can I tell the kernel not to probe DMA for a specific harddisk (e.g. 
> hda). My first Drive (hda) is a Compact-Flash Card which can not do DMA. 
> The kernel tries at boot to switch to DMA but fails. If I use ide=nodma, 
> the kernel boots about 2 minutes faster, but then I can not switch on 
> DMA for the second Drive (hdc) which is a normal Harddisk. Do I have to 
> live with this 2 minutes waiting time or is there another solution? I 
> did not find any kernel-parameter for this purpose.
> 
> Sorry if I ask here, but I can not find any solution, and I asked 
> already in other groups.

For the current kernel and libata you can use libata.dma=3, and it will
select DMA for disk (1) + CD (2) but not CF cards. With the older IDE it
should be sufficient to use hda=nodma

Alan
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