linux-kernel - Regression with i915 and suspend on Thinkpad x220

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Message-ID: <1306040157.3322.11.camel@calx>
Date:	Sat, 21 May 2011 23:55:57 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	dri-devel <dri-devel@...ts.freedesktop.org>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Regression with i915 and suspend on Thinkpad x220

I've got a new Thinkpad x220 which won't wake up from suspend with
2.6.39, but works fine with 2.6.37.

I bisected it down to this cset:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=4efe070896e1f7373c98a13713e659d1f5dee52a

drm/i915: make the blitter report buffer modifications to the FBC unit

Without this change, blits to the front buffer won't invalidate FBC
state, causing us to scan out stale data.  Make sure we update these
bits on every FBC enable, since they may get clobbered if we shut off
the display.

After this changeset, resuming wakes up the backlight, but fails to
restore video and leaves the CPU spinning and the keyboard unresponsive.

Before this changeset, but some distance after 2.6.37, most of the
screen isn't painted, but I can still log on and successfully
suspend/resume.

I've attached my .config and lscpi output.

-- 
Mathematics is the supreme nostalgia of our time.

View attachment ".config" of type "text/x-mpsub" (69000 bytes)

View attachment "lspci" of type "text/plain" (6537 bytes)