Re: [PATCH v2] powerpc/cpuidle: Set CPUIDLE_FLAG_POLLING for snooze state

[Vaidyanathan Srinivasan <svaidy@linux.ibm.com>]

* Vishal Chourasia <vishalc@linux.vnet.ibm.com> [2022-11-19 14:19:52]:

> On Mon, Nov 14, 2022 at 08:26:11PM +0530, Aboorva Devarajan wrote:
> > During the comparative study of cpuidle governors, it is noticed that the
> > menu governor does not select CEDE state in some scenarios even though when
> > the sleep duration of the CPU exceeds the target residency of the CEDE idle
> > state this is because the CPU exits the snooze "polling" state when snooze
> > time limit is reached in the snooze_loop(), which is not a real wake up
> > and it just means that the polling state selection was not adequate.
> > 
> > cpuidle governors rely on CPUIDLE_FLAG_POLLING flag to be set for the
> > polling states to handle the condition mentioned above.
> > 
> > Hence, set the CPUIDLE_FLAG_POLLING flag for snooze state (polling state)
> > in powerpc arch to make the cpuidle governor work as expected.
> > 
> > Reference Commits:
> > 
> > - Timeout enabled for snooze state:
> >   commit 78eaa10f027c
> >   ("cpuidle: powernv/pseries: Auto-promotion of snooze to deeper idle state")
> > 
> > - commit dc2251bf98c6
> >   ("cpuidle: Eliminate the CPUIDLE_DRIVER_STATE_START symbol")
> > 
> > - Fix wakeup stats in governor for polling states
> >   commit 5f26bdceb9c0
> >   ("cpuidle: menu: Fix wakeup statistics updates for polling state")
> > 
> > Signed-off-by: Aboorva Devarajan <aboorvad@linux.vnet.ibm.com>
> > ---
> > 
> > Changelog: (v1 -> v2)
> > 
> > Added CPUIDLE_POLLING_FLAG to the correct cpuidle_state struct.
> > 
> > Previous version of the patch is stale which was sent by mistake, this 
> > is the correct version which is tested on powernv, pseries (shared and 
> > dedicated partitions)
> > 
> >  drivers/cpuidle/cpuidle-powernv.c | 5 ++++-
> >  drivers/cpuidle/cpuidle-pseries.c | 8 ++++++--
> >  2 files changed, 10 insertions(+), 3 deletions(-)

Hi Aboorva,

Thanks for the patch. This fixes the unpredictable idle state
selection issue under differ idle interval patterns.

Reviewed-by: Vaidyanathan Srinivasan <svaidy@linux.ibm.com>

--Vaidy