From ec4867355244755fb5c06037ad2fff760701b465 Mon Sep 17 00:00:00 2001

From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

Date: Tue, 16 May 2017 14:19:44 +0530

Subject: [PATCH] powerpc/powernv/idle: Decouple Timebase restore & Per-core

 SPRs restore

References: bsc#1055121

Patch-mainline: v4.13-rc1

Git-commit: ec4867355244755fb5c06037ad2fff760701b465

On POWER8, in case of

   -  nap: both timebase and hypervisor state is retained.

   -  fast-sleep: timebase is lost. But the hypervisor state is retained.

   -  winkle: timebase and hypervisor state is lost.

Hence, the current code for handling exit from a idle state assumes

that if the timebase value is retained, then so is the hypervisor

state. Thus, the current code doesn't restore per-core hypervisor

state in such cases.

But that is no longer the case on POWER9 where we do have stop states

in which timebase value is retained, but the hypervisor state is

lost. So we have to ensure that the per-core hypervisor state gets

restored in such cases.

Fix this by ensuring that even in the case when timebase is retained,

we explicitly check if we are waking up from a deep stop that loses

per-core hypervisor state (indicated by cr4 being eq or gt), and if

this is the case, we restore the per-core hypervisor state.

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Acked-by: Michal Suchanek <msuchanek@suse.de>

---

 arch/powerpc/kernel/idle_book3s.S | 7 ++++---

 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S

index 4898d676dcae..afd029f1039b 100644

--- a/arch/powerpc/kernel/idle_book3s.S

+++ b/arch/powerpc/kernel/idle_book3s.S

@@ -731,13 +731,14 @@ timebase_resync:

 	 * Use cr3 which indicates that we are waking up with atleast partial

 	 * hypervisor state loss to determine if TIMEBASE RESYNC is needed.

 	 */

-	ble	cr3,clear_lock

+	ble	cr3,.Ltb_resynced

 	/* Time base re-sync */

 	bl	opal_resync_timebase;

 	/*

-	 * If waking up from sleep, per core state is not lost, skip to

-	 * clear_lock.

+	 * If waking up from sleep (POWER8), per core state

+	 * is not lost, skip to clear_lock.

 	 */

+.Ltb_resynced:

 	blt	cr4,clear_lock

 	/*

-- 

2.10.2