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hard disk DMA not enabled on newly built kernel

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From: Hao Song <baritonelw@...>
To: kernelnewbies <kernelnewbies@...>
Subject: hard disk DMA not enabled on newly built kernel
Date: Sunday, August 24, 2008 - 4:08 am

hi, folks:
I've just built a kernel from vanilla linux-2.6.26.3 source code, with no
third-party patches.
But according to hdparm, the DMA mode of my hard disk is disabled. And when
I tried to enable DMA for the hard disk with hdparm, I got a "Operation not
permitted" error. And hdparm benchmark data for the hard disk is quite low,
"Timing buffered disk reads" only 2~3 MB/s (normally, it should be 25~30
MB/s).

I noticed that in dmesg output, there are warning messages like:
pata_via 0000:00:0f.1: no available native port
pata_acpi 0000:00:0f.1: no available native port
I found a post in LKML archive http://lkml.org/lkml/2007/8/24/381 saying
that this is a bug in IDE legacy mode code. So is it possible to circumvent
this problem in my kernel config? Currently I compile all device drivers
into the kernel binary rather than separate modules.

The IDE interface is
00:0f.1 IDE interface: VIA Technologies, Inc.
VT82C586A/B/VT82C686/A/B/VT823x/A/C PIPC Bus Master IDE (rev 06)
as appeared in the lspci listing.

Thanks!
-- 
$BAW9@(B
Song, Hao
Institute for Theoretical Computer Science
Tsinghua University, Beijing, P.R.China
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hard disk DMA not enabled on newly built kernel, Hao Song, (Sun Aug 24, 4:08 am)