linux-kernel - Re: [PATCH] libata: fix combined mode (was Re: Happy New Year (and v2.6.20-rc3 released))

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Message-ID: <459AC808.1030807@pobox.com>
Date:	Tue, 02 Jan 2007 16:00:56 -0500
From:	Jeff Garzik <jgarzik@...ox.com>
To:	Alan <alan@...rguk.ukuu.org.uk>, Linus Torvalds <torvalds@...l.org>
CC:	Alessandro Suardi <alessandro.suardi@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] libata: fix combined mode (was Re: Happy New Year (and
 v2.6.20-rc3 released))

Alan wrote:
> This is a slight variant on the patch I posted December 16th to fix
> libata combined mode handling. The only real change is that we now
> correctly also reserve BAR1,2,4. That is basically a neatness issue.
> 
> Jeff was unhappy about two things
> 
> 1. That it didn't work in the case of one channel native one channel
> legacy. 

> This is a silly complaint because the SFF layer in libata doesn't handle
> this case yet anyway.

Yes, it's "silly" people people use configurations you find inconvenient.

At least one embedded x86 case cares, that I know of.  They only needed 
to make two minor changes to make it work.

> 2. The case where combined mode is in use and IDE=n. 

> In this case the libata quirk code reserves the resources in question
> correctly already.

Not /all/ the resources.  And YOU were the person harping me about 
acquiring all resources, so that even races no one cares about[1] are 
avoided.

But those two items were just from my five-minute, on-vacation review. 
Obvious bug #3:

The code no long reserves resources for the "extra" PCI BAR that often 
exists on PCI controllers regardless of legacy/native mode.  Previously, 
the code called pci_request_regions() to reserve ALL regions attached to 
the PCI device.

You have suddenly decided that it's OK to --not reserve at all-- these 
additional regions.

Proof:  The AHCI PCI BAR (#5, zero-based) is clearly NOT reserved, even 
though we talk to it, in piix_disable_ahci() of ata_piix.c.

	Jeff

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