powerpc: Default arch idle could cede processor on pseries
authorVaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Thu, 5 Sep 2013 18:55:06 +0000 (23:55 +0530)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 27 Sep 2013 00:18:01 +0000 (17:18 -0700)
commitd08bfff9ef39c029befa68b2641ad2f7a2c894b6
tree1e8050f424710f962a89c9fcb466eef9bbc73201
parentd8ba750f9a2feb07bb6f0448807907b674ca4525
powerpc: Default arch idle could cede processor on pseries

commit 363edbe2614aa90df706c0f19ccfa2a6c06af0be upstream.

When adding cpuidle support to pSeries, we introduced two
regressions:

  - The new cpuidle backend driver only works under hypervisors
    supporting the "SLPLAR" option, which isn't the case of the
    old POWER4 hypervisor and the HV "light" used on js2x blades

  - The cpuidle driver registers fairly late, meaning that for
    a significant portion of the boot process, we end up having
    all threads spinning. This slows down the boot process and
    increases the overall resource usage if the hypervisor has
    shared processors.

This fixes both by implementing a "default" idle that will cede
to the hypervisor when possible, in a very simple way without
all the bells and whisles of cpuidle.

Reported-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Acked-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
arch/powerpc/platforms/pseries/setup.c