[Intel-gfx] [PATCH] tests/pm_rps: Add a new testcase to provoke the "stuck at max" bug

[Chris Wilson]

On Wed, Mar 26, 2014 at 10:17:51PM +0100, Daniel Vetter wrote:
> Note that the sleep(5); to fully idle the gpu is _really_ important.
> Without it the bug is not exhibited.
> 
> The issue at hand is that after gem_quiescent_gpu we are at max
> (expected, since the blocking waits peg to max), but then we never go
> down to a lower freq again until we're fully idle. The tiny load is
> sufficient to keep the gpu at max. I've played around with this a bit
> and even ridiculously low loads (like one MI_STORE per 50ms) are
> enough to keep the gpu at max freq.

commit 2754436913b94626a5414d82f0996489628c513d
Author: Deepak S <deepak.s at intel.com>
Date:   Mon Jan 27 21:35:05 2014 +0530

    drm/i915: Disable/Enable PM Intrrupts based on the current freq.

as expected is complete and utter codswallop.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre