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Message-ID: <446C5B83.9000305@gmail.com>
Date: Thu, 18 May 2006 20:33:23 +0900
From: Tejun Heo <htejun@gmail.com>
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To: albertl@mail.com
CC: Andrew Morton <akpm@osdl.org>, jeff@garzik.org, linux-ide@vger.kernel.org,
       linux-kernel@vger.kernel.org, torvalds@osdl.org
Subject: Re: [RFT] major libata update
References: <20060515170006.GA29555@havoc.gtf.org>	<20060516190507.35c1260f.akpm@osdl.org>	<446AAB3C.6050303@gmail.com> <20060516215610.2b822c00.akpm@osdl.org> <446AB12C.10001@gmail.com> <446AC418.4070704@gmail.com> <446C5957.9040404@tw.ibm.com>
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Albert Lee wrote:
>> To sum up, it happens when the master slot is occupied by an ATAPI
>> device and the corresponding slave slot is empty.  The slave slot
>> reports ATAPI signature (probably duplicated from the master) and passes
>> all legacy presence test thus resulting in timeout on IDENTIFY.
>>
> 
> This problem was seen with PATA Promise 20275 adapter + IBM DVD-RAM drive.
> Single master device configuration, no slave device.
> The master device acts as slave and creates a phantom slave device.
> (http://marc.theaimsgroup.com/?l=linux-ide&m=113151315602979&w=2)
> 
> The problem was later fixed by Tejun's ata_exec_internal() patch:
> (http://marc.theaimsgroup.com/?l=linux-ide&m=113455450809405&w=2)
> After the patch, the phantom device is finally detected by ata_dev_identify().
> 
> Libata uses polling PIO for IDENTIFY DEVICE before this major update.
> The polling PIO finds something wrong when it reads a 0x00 device status.
> So, the phantom device is detected quite quickly.
> 
> With irq-driven PIO, maybe the phantom device is only detected after time-out.
> So it takes longer (30 secs) to detect the phantom device.
> 
> No good idea how to fix this. Maybe read more registers to see whether the
> phantom device can be detected early before the IDENTIFY DEVICE.
> 

Does the Promise controller show the ghosting problem again with the 
recent updates?  ata_piix can be fixed by using PCS present bits.  I 
don't know about Promise though.

-- 
tejun
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