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tests/pm_rps: Add a new testcase to provoke the "stuck at max" bug

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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.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Daniel Vetter 2014-03-26 22:15:12 +01:00
parent 669a2fca6c
commit 961a46c82b
1 changed files with 40 additions and 0 deletions
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40
tests/pm_rps.c
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@ -522,6 +522,43 @@ static void reset(void)
idle_check();
}
static void blocking(void)
{
int pre_freqs[NUMFREQ];
int post_freqs[NUMFREQ];
int fd = drm_open_any();
igt_assert(fd >= 0);
/*
* quiescent_gpu upsets the gpu and makes it get pegged to max somehow.
* Don't ask.
*/
sleep(10);
igt_debug("Apply low load...\n");
load_helper_run(LOW);
stabilize_check(pre_freqs);
load_helper_stop();
sleep(5);
igt_debug("Kick gpu hard ...\n");
/* This relies on the blocking waits in quiescent_gpu and the kernel
* boost logic to ramp the gpu to full load. */
gem_quiescent_gpu(fd);
gem_quiescent_gpu(fd);
igt_debug("Apply low load again...\n");
load_helper_run(LOW);
stabilize_check(post_freqs);
load_helper_stop();
matchit(pre_freqs, post_freqs);
igt_debug("Removing load...\n");
idle_check();
}
static void pm_rps_exit_handler(int sig)
{
if (origfreqs[MIN] > readval(stuff[MAX].filp)) {
@ -583,4 +620,7 @@ igt_main
igt_subtest("reset")
reset();
igt_subtest("blocking")
blocking();
}