powerpc/powernv/idle: Decouple Timebase restore & Per-core SPRs restore

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>

diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 4898d676dcaef1d02600c5c75ef13ceca1fc8c69..afd029f1039bb0e60ab8cf54bdc77ad8c239126c 100644 (file)
--- 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
 
        /*