[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <4977BBBD.90704@ru.mvista.com>
Date: Thu, 22 Jan 2009 03:20:13 +0300
From: Sergei Shtylyov <sshtylyov@...mvista.com>
To: Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: Mikael Pettersson <mikpe@...uu.se>,
Hugh Dickins <hugh@...itas.com>,
Jeff Garzik <jgarzik@...hat.com>,
"Rafael J. Wysocki" <rjw@...k.pl>, linux-ide@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: 2.6.29-rc libata sff 32bit PIO regression
Hello, I wrote:
>>>>>> > I've a Dell Precision 670 here (four-year-old EM64T Xeon with
>>>>>> ata_piix)
>>>>>> > which doesn't like your commit
>>>>>> 871af1210f13966ab911ed2166e4ab2ce775b99d
>>>>>> > libata: Add 32bit PIO support. Full dmesg (and .config)
>>>>>> attached, but
>>>>>> > here's an extract showing the start of the error messages on
>>>>>> ata2:
>>>>>>
>>>>> Cool - so we need two different 32bit PIO methods - at least
>>>>> according to
>>>>> the docs for the AMD we should use entirely 32bit I/O there. Fun fun
>>>>>
>>>> Could you refer me to the exact AMD doc that requires that?
>>>>
>>>
>>> AMD762 page 82, under DevB:1x40 bit 14 and bit 12
>>>
>>
>> What exactly AMD-762 document has this? I'm not seeing it in either
>> stasheet ot software/BIOS design guide. Besides, AMD-762 is a north
>> bridge and doesn't include IDE.
>
> Finally found it in the AMD-768 datasheet.
>
>>> "Note: only 32-bit writes to the data port are allowed when this bit is
>>> set."
>>>
>>
>> Now tell me who forces you to set that bit (I assume it's the write
>> buffer enable) for the ATAPI devices?
>
> Yes, it's the write buffer enable (about which I have written already).
IMHO, this is the same situation as with the prefetch -- you want to
avoid additional data read (write in this case) cycles to with an ATAPI
device, so you have to turn it off.
MBR, Sergei
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists