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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Date:	Mon, 23 Feb 2009 12:02:23 -0800
From:	Eric Anholt <eric@...olt.net>
To:	Maciej Rutecki <maciej.rutecki@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"lenb@...nel.org" <lenb@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	mjg@...hat.com, "Rafael J. Wysocki" <rjw@...k.pl>,
	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 Mon, 2009-02-23 at 15:46 +0100, Maciej Rutecki wrote:
> 2.6.29-rc5 and 2.6.29-rc5-git6 work OK. In 2.6.29-rc6 XWindow (KDM)
> doesn't start, from dmesg:
> 
> [   18.170614] [drm] Initialized drm 1.1.0 20060810
> [   18.247445] pci 0000:00:02.0: PCI INT A -> GSI 16 (level, low) -> IRQ 16
> [   18.247455] pci 0000:00:02.0: setting latency timer to 64
> [   18.249610] mtrr: type mismatch for d0000000,10000000 old:
> write-back new: write-combining
> [   18.249621] [drm] MTRR allocation failed
> [   18.249622] .  Graphics performance may suffer.
> [   18.249658] pci 0000:00:02.0: irq 27 for MSI/MSI-X
> [   18.249691] [drm] Initialized i915 1.6.0 20080730 on minor 0
> [   18.290152] mtrr: type mismatch for d0000000,10000000 old:
> write-back new: write-combining
> [   18.567435] set status page addr 0x00043000
> [   18.567463] [drm:i915_set_status_page] *ERROR* can not ioremap
> virtual address for G33 hw status page

The non-GEM G33 HWS support is wrong, and has been more or less broken
since inception (only now it's failing at startup instead of just being
slow).  It's doing a mapping of the framebuffer when it should be using
a cached mapping of the page backing the framebuffer address.

For a quick fix, converting to ioremap_wc will shut the kernel up and
get us the old ioremap behavior (whatever the MTRR said, which happens
to be WC).

-- 
Eric Anholt
eric@...olt.net                         eric.anholt@...el.com



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