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Date: Thu, 22 Aug 2002 20:19:18 -0700 (PDT)
From: Andre Hedrick <andre@linux-ide.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
cc: Jeff Garzik <jgarzik@mandrakesoft.com>,
       "'Linux Kernel'" <linux-kernel@vger.kernel.org>
Subject: Re: IDE-flash device and hard disk on same controller
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Oh and it is only useful for borken things like LINBIOS and other
braindead systems like ARM that violate the 31 second rule of POST.

RMK, don't take it personally, but ARM is a headache of the nth degree.
You and I know it, otherwise I would not have a raw TTL IDE PCI card to
mimic your arch.

Cheers,

On 22 Aug 2002, Eric W. Biederman wrote:

> Jeff Garzik <jgarzik@mandrakesoft.com> writes:
> 
> > Eric W. Biederman wrote:
> > > I don't see any checking for the ATA bsy flag before you start sending
> > > commands.  I have seen the current IDE code fail too many times if I
> > > boot to fast, because of a lack of this one simple test.  So I don't
> > > see how this could be considered a proper probe.
> > 
> > 
> > There is no ATA bsy flag check at only one point, and that is before EXECUTE
> > DEVICE DIAGNOSTIC is issued.  The idea with this command is that it pretty much
> > stomps up and down the ATA bus, trouncing ongoing activity in the process.
> 
> The problem is that immediately after bootup ATA devices do not respond until
> their media has spun up.  Which is both required by the spec, and observed in
> practice.   Which is likely a problem if this code is run a few seconds after
> bootup.  Which makes it quite possible the drive will ignore the EXECUTE DEVICE
> DIAGNOSTICS and your error code won't be valid when the bsy flag
> clears.   I don't know how serious that would be. 
> 
> I can test and find out but I would rather confine my testing to
> commands that look like they will stay within the realms of
> predictable behavior.
> 
> And yes with LinuxBIOS I can reliably boot up fast enough to make this
> problem show up in practice.
> 
> Eric
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Andre Hedrick
LAD Storage Consulting Group

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