Re: [PATCH] sata_nv: Don't attempt using ADMA for (READ|SET)_MAX commands

[Robert Hancock <hancockr@shaw.ca>]

Mark Lord wrote:
> Alan Cox wrote:
>> On Fri, 13 Apr 2007 13:08:31 -0400
>> Kyle McMartin <kyle@canonical.com> wrote:
>>
>>> READ_NATIVE_MAX and SET_MAX were causing timeouts on sata_nv 
>>> controllers.
>>> Disabling ADMA helped, but that is quite a large hammer to use. 
>>> Reverting
>>> 382a6652e91b34d5480cfc0ed840c196650493d4 also helped, but we might as 
>>> well
>>> fix it right, instead of disabling the performance gain on cache flushes
>>> by using ADMA mode.
>>
>> Probably not going to make any performance difference to blacklist all
>> non-data commands or all but a few like cache-flush. 
> 
> I agree.  The Pacific Digital ADMA stuff had some quirks for various 
> non-data
> commands as well, and the sensible thing was to just not use ADMA for 
> anything
> other than READs/WRITEs and possible CACHE FLUSHes.

I'm told by NVidia that non-data commands should be fine in ADMA mode, 
except for those that require reading back a result taskfile (which 
can't be done in ADMA mode). The patch in libata-dev which I mentioned 
in another email will ensure that we don't try to use ADMA for such 
commands, so this patch should not be needed.

-- 
Robert Hancock      Saskatoon, SK, Canada
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