Understanding DMA/NoDMA options and fixes

Rick Stevens rstevens at vitalstream.com
Thu Jul 21 20:57:47 UTC 2005


Alan Cox wrote:
> On Llu, 2005-07-18 at 21:02 -0500, John Best wrote:
> 
>>Are there jumpers on the IDE devices that should be looked
>>at/investigated?   If I hooked up devices using Cable Select vs
>>physically jumpering devices to primary/secondary will it make any
>>difference?

Sorry to break in, Alan.  Cable select is bloody evil.  Do not use it
if you value your sanity.  IMHO after dealing with over 3,000 Linux-
based servers, "Cable select:  Just say 'No'."

>>             Can I tell which device or devices are responsible for the
>>DMA issues?  Can I tell when buying or looking at a device whether it
>>supports the proper dma standards?  Can I go to a web site or other
>>location to check for compatible dma devices?
> 
> 
> Its almost certainly a Linux problem, especially if it worked before
> FC3. There are afaik no devices sold today (or in recent history) with
> broken DMA. There are however limitations on some older controllers.
> Those limitations haven't mysteriously changed in FC3/4 however.
> 
> Please file a bug and assign it to my work incarnation <alan at redhat...>.
> Include the controller in question, lspci -v output, the devices
> attached and dmesg output.
> 
> Alan
> 


-- 
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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
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- Millihelen, adj: The amount of beauty required to launch one ship. -
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