i915: high power consumption after suspend/resume

From: Andrew Lutomirski <luto@mit.edu>
To: dri-devel@lists.sf.net, linux-kernel@vger.kernel.org,
	intel-gfx@lists.freedesktop.org
Subject: i915: high power consumption after suspend/resume
Date: Sat, 3 Oct 2009 12:39:59 -0400	[thread overview]
Message-ID: <cb0375e10910030939v8d03df7m861a2f05219f173c@mail.gmail.com> (raw)

Hi-

First, thanks for all the great work on i915's power saving features
-- power consumption on my laptop (Lenovo X200s) is now almost as low
on Linux as on Windows.

After a suspend/resume cycle, though, my power consumption usually
goes up by over a watt.  I think this is due to i915, because of an
experiment I did:

1. Boot with modesetting off into single user mode.
2. Suspend and resume
3. Reload i915 with modesetting on.  Power consumption is low.
4. Suspend and resume.  Power consumption is high.
5. Unbind and rebind i915.  Power consumption is high.
6. Suspend.  System hangs (seperate bug, I guess).

I get similar results if I boot single user with modesetting on: power
consumption is low, becomes high after suspend/resume, and goes low
again after rebinding i915.

This is on 2.6.32-rc1 + a little (i.e. 84d88d5d4e from Linus' tree
plus an ext4 fix).  I'm having trouble reproducing any of this on
2.6.31.

Thanks,
Andy