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Bug 117179 - aic7xxx / aic79xx drivers have highmem IO disabled
aic7xxx / aic79xx drivers have highmem IO disabled
Product: Red Hat Enterprise Linux 2.1
Classification: Red Hat
Component: kernel (Show other bugs)
i686 Linux
medium Severity medium
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Assigned To: Jim Paradis
Brian Brock
Depends On:
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Reported: 2004-03-01 05:06 EST by Martin Wilck
Modified: 2013-08-05 21:04 EDT (History)
2 users (show)

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Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Last Closed: 2005-12-05 16:30:06 EST
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RHEL 7.3 requirements from Atomic Host:
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Description Martin Wilck 2004-03-01 05:06:16 EST
Description of problem:
The aic7xxx and aic79xx drivers have high memory IO disabled (the
can_dma_32/single_sg_ok flags are unset in the SCSI driver template
structure). This is because the driver sources check for the
CONFIG_HIGHIO macro which, in the AS2.1 kernels, is persent in the
kernel .config, but not set in include/linux/autoconf.h. 

This will lead to performance losses in systems wirth large memory.

Version-Release number of selected component (if applicable):
2.4.9-e.xy up to 2.4.9-e.38

How reproducible:

Steps to Reproduce:
1.Install RHAS2.1 on system with aic7xxx or aic79xx controller and
>1GB memory.
2. Use "new" driver (aic7xxx 6.x.y) for aix7xxx. 
3. Do I/O.
Actual results:
System uses bounce buffers.

Expected results:
System doesn't need bounce buffers.

Additional info:
I came a cross this problem accidentally by comparing the methods how
different driver sources check for the presence of the can_dma_32
field in the SCSI host template.
Comment 1 Jim Paradis 2005-12-05 16:30:06 EST
This issue is outside the scope of the current support status for RHEL2.1.  No
fix is planned.

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