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Date: Mon, 16 Jan 2012 15:27:08 -0500
From: Jeff Garzik <jeff@garzik.org>
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To: Linus Torvalds <torvalds@linux-foundation.org>
CC: Alan Cox <alan@lxorguk.ukuu.org.uk>, Matthew Garrett <mjg@redhat.com>,
        Lin Ming <ming.m.lin@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>, linux-ide@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [git patches] libata updates for 3.3
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On 01/16/2012 03:21 PM, Linus Torvalds wrote:
> On Mon, Jan 16, 2012 at 12:02 PM, Linus Torvalds
> <torvalds@linux-foundation.org>  wrote:
>>>
>>> http://www.codon.org.uk/~mjg59/tmp/ahci_quirk_cleanup.diff
>>
>> Hmm. This with just a setup option to enable it might well be good
>> enough. No need for whitelists/blacklists, since we couldn't maintain
>> those sanely anyway.
>
> That patch doesn't work for me. I get a panic in ahci_enable_ahci,
> looks like 'mmio' is bogus there (attempting to dereference 0x01ffe6).
>
> I notice that the PIIX device doesn't have any MMIO at all, it's all
> PIO. Maybe there is some "need to enable MMIO thing" too. Or maybe I
> used the wrong PCI ID when I added it to the quirk table.

Part of the problem with force-enable is that the MMIO BAR may need a 
value, and not have it.  That, and an expectations mismatch between BIOS 
and kernel WRT mode (IDE/AHCI) has always been the reason why 
'ahci=force' never made it in.  It just never seemed to be reliable broadly.

I'm happy with anything we can get working reliably, even with the 
obvious proviso that 'ahci=force' would be a default-off, user-enabled 
option.  It's always been motherboard/BIOS issues that got in the way.

	Jeff