linux-kernel - Re: [Linux 2.6.29-rc6] [drm:i915_set_status_page] *ERROR* can not ioremap virtual address for G33 hw status page

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Message-ID: <alpine.LFD.2.00.0902241354220.3111@localhost.localdomain>
Date:	Tue, 24 Feb 2009 13:59:04 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Airlie <airlied@...hat.com>
cc:	Ingo Molnar <mingo@...e.hu>, Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Andy Isaacson <adi@...apodia.org>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Eric Anholt <eric@...olt.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"lenb@...nel.org" <lenb@...nel.org>, mjg@...hat.com,
	Andrew Morton <akpm@...ux-foundation.org>, rui.zhang@...el.com
Subject: Re: [Linux 2.6.29-rc6] [drm:i915_set_status_page] *ERROR* can not
 ioremap virtual address for G33 hw status page



On Wed, 25 Feb 2009, Dave Airlie wrote:
> > 
> > The other question is, why did the ioremap_wc() fail? Why doesnt 
> > it fall back to UC transparently?
>
> I'm sort of worried the drivers are going to end up doing, which at
> the moment is the only option that will work.
> 
> blah = ioremap_wc();
> if (!blah)
> 	blah = ioremap_nocache();
> 
> which seems pointless so this is a good point, where is the fallback?

I agree.

We should not fail the ioremap_wc(), we should just fall back to nocache, 
(possibly with a warning). In fact I thought we did exactly that, but 
maybe it only happens in certain directions.

			Linus
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