linux-kernel - Re: a7839e96 (PNP: increase max resources) breaks my ALSA intel8x0 sound card

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Message-Id: <200802141151.40396.bjorn.helgaas@hp.com>
Date:	Thu, 14 Feb 2008 11:51:39 -0700
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Robert Hancock <hancockr@...w.ca>,
	Andrew Morton <akpm@...ux-foundation.org>, avuton@...il.com,
	yakui.zhao@...el.com, shaohua.li@...el.com, trenn@...e.de,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	alsa-devel@...a-project.org
Subject: Re: a7839e96 (PNP: increase max resources) breaks my ALSA intel8x0 sound card

On Tuesday 05 February 2008 01:12:46 pm Bjorn Helgaas wrote:
> On Tuesday 05 February 2008 11:15:12 am Linus Torvalds wrote:
> > No, you don't need any quirks: you just do an "insert_resource()" and 
> > ignore the error return. If the (bogus) PnP resource clashes with the 
> > (correct) hardware PCI resource, the insert will simply fail. No quirks
> > needed.

> I'll play with your insert_resource() idea and see if I can figure
> something out.

Sorry for the delay.  I did work on this, but I don't see how this
can work.  pcibios_init() marks its reservations as not busy, so the
subsequent PNP request doesn't fail, even if it clashes.

The PNP system driver is an fs_initcall(), so it already happens after
pcibios_init():

  1) register ACPI PCI root bridge driver, which enumerates PCI
       devices behind the bridge
  2) pcibios_init() -> pcibios_resource_survey() -> request_resource()
  3) register PNP system driver -> request_region()
  4) register intel8x0 sound driver and reserve resources
       (conflict happens here)

We have reservations in this order:

  febf8000-febfbfff : 0000:00:1b.0 -- from pcibios_resource_survey (!busy)
  febfa000-febfac00 : pnp 00:08    -- from PNP system driver (!busy)
  febf8000-febfbfff : ICH HD audio -- fails because it spans the PNP region

The PNP reservation succeeds even though the PCI reservation has
already happened, so I don't see how we can do this without a
quirk that ignores the bogus PNP resources.

Bjorn
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