tree 447d506fd8a36e14853216a0bbbbb540b10f7304
parent 88c2d0b6fa753c63047fad92eac94c376ee4e568
author Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> 1378407306 +0530
committer Benjamin Herrenschmidt <benh@kernel.crashing.org> 1378863714 +1000

powerpc: Default arch idle could cede processor on pseries

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>
CC: <stable@vger.kernel.org>