From 22c6663dc69a042a7b4158f162582b4b1ba7a4b7 Mon Sep 17 00:00:00 2001
From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
Date: Tue, 16 May 2017 14:19:47 +0530
Subject: [PATCH] powerpc/powernv/idle: Use Requested Level for restoring state
on P9 DD1
References: bsc#1055121
Patch-mainline: v4.13-rc1
Git-commit: 22c6663dc69a042a7b4158f162582b4b1ba7a4b7
On Power9 DD1 due to a hardware bug the Power-Saving Level Status
field (PLS) of the PSSCR for a thread waking up from a deep state can
under-report if some other thread in the core is in a shallow stop
state. The scenario in which this can manifest is as follows:
1) All the threads of the core are in deep stop.
2) One of the threads is woken up. The PLS for this thread will
correctly reflect that it is waking up from deep stop.
3) The thread that has woken up now executes a shallow stop.
4) When some other thread in the core is woken, its PLS will reflect
the shallow stop state.
Thus, the subsequent thread for which the PLS is under-reporting the
wakeup state will not restore the hypervisor resources.
Hence, on DD1 systems, use the Requested Level (RL) field as a
workaround to restore the contents of the hypervisor resources on the
wakeup from the stop 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/include/asm/paca.h | 2 ++
arch/powerpc/kernel/asm-offsets.c | 1 +
arch/powerpc/kernel/idle_book3s.S | 13 ++++++++++++-
3 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index 1c09f8fe2ee8..77f60a0f1405 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -177,6 +177,8 @@ struct paca_struct {
* to the sibling threads' paca.
*/
struct paca_struct **thread_sibling_pacas;
+ /* The PSSCR value that the kernel requested before going to stop */
+ u64 requested_psscr;
#endif
#ifdef CONFIG_PPC_STD_MMU_64
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 709e23425317..e15c178ba079 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -742,6 +742,7 @@ int main(void)
OFFSET(PACA_THREAD_MASK, paca_struct, thread_mask);
OFFSET(PACA_SUBCORE_SIBLING_MASK, paca_struct, subcore_sibling_mask);
OFFSET(PACA_SIBLING_PACA_PTRS, paca_struct, thread_sibling_pacas);
+ OFFSET(PACA_REQ_PSSCR, paca_struct, requested_psscr);
#endif
DEFINE(PPC_DBELL_SERVER, PPC_DBELL_SERVER);
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 6c9920d9221c..98a6d07ecb5c 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -379,6 +379,7 @@ _GLOBAL(power9_idle_stop)
mfspr r5,SPRN_PSSCR
andc r5,r5,r4
or r3,r3,r5
+ std r3, PACA_REQ_PSSCR(r13)
mtspr SPRN_PSSCR,r3
LOAD_REG_ADDR(r5,power_enter_stop)
li r4,1
@@ -498,12 +499,22 @@ pnv_restore_hyp_resource_arch300:
LOAD_REG_ADDRBASE(r5,pnv_first_deep_stop_state)
ld r4,ADDROFF(pnv_first_deep_stop_state)(r5)
- mfspr r5,SPRN_PSSCR
+BEGIN_FTR_SECTION_NESTED(71)
+ /*
+ * Assume that we are waking up from the state
+ * same as the Requested Level (RL) in the PSSCR
+ * which are Bits 60-63
+ */
+ ld r5,PACA_REQ_PSSCR(r13)
+ rldicl r5,r5,0,60
+FTR_SECTION_ELSE_NESTED(71)
/*
* 0-3 bits correspond to Power-Saving Level Status
* which indicates the idle state we are waking up from
*/
+ mfspr r5, SPRN_PSSCR
rldicl r5,r5,4,60
+ALT_FTR_SECTION_END_NESTED_IFSET(CPU_FTR_POWER9_DD1, 71)
cmpd cr4,r5,r4
bge cr4,pnv_wakeup_tb_loss /* returns to caller */
--
2.10.2