From: Ian Munsie <imun...@au1.ibm.com>
If a doorbell IPI comes in while a thread is in nap power saving, the
doorbell interrupt won't be replayed by the hardware since it is edge
sensitive. Currently we are not replaying these interrupts in software,
which can cause threads to miss IPIs that come in during power saving
and eventually will result in an RCU warning from rcu_sched that it has
detected a stalled CPU.
This patch fixes the issue by testing if a doorbell caused the thread to
come out of power saving and sets the corresponding bit in the paca to
indicate a doorbell happened, which will then be handled by the existing
interrupt replay code.
This is not an issue with other interrupts that can wake a thread
(external, decrementer) as they are level sensitive and will continue to
be asserted by the hardware.
Signed-off-by: Ian Munsie <imun...@au1.ibm.com>
---
arch/powerpc/include/asm/reg.h | 5 ++++-
arch/powerpc/kernel/idle_power7.S | 23 +++++++++++++++++++----
2 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 5c6fbe2..dd8a071 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -549,14 +549,17 @@
#define SRR1_ISI_NOPT 0x40000000 /* ISI: Not found in hash */
#define SRR1_ISI_N_OR_G 0x10000000 /* ISI: Access is no-exec or G */
#define SRR1_ISI_PROT 0x08000000 /* ISI: Other protection
fault */
-#define SRR1_WAKEMASK 0x00380000 /* reason for wakeup */
+#define SRR1_WAKEMASK 0x003c0000 /* reason for wakeup [42:45]
*/
+#define SRR1_WAKESHIFT 18
#define SRR1_WAKESYSERR 0x00300000 /* System error */
#define SRR1_WAKEEE 0x00200000 /* External interrupt */
#define SRR1_WAKEMT 0x00280000 /* mtctrl */
#define SRR1_WAKEHMI 0x00280000 /* Hypervisor maintenance */
#define SRR1_WAKEDEC 0x00180000 /* Decrementer interrupt */
+#define SRR1_WAKEDBELLP 0x00140000 /* Privileged Doorbell */
#define SRR1_WAKETHERM 0x00100000 /* Thermal management interrupt */
#define SRR1_WAKERESET 0x00100000 /* System reset */
+#define SRR1_WAKEDBELLH 0x000c0000 /* Hypervisor Doorbell */
#define SRR1_WAKESTATE 0x00030000 /* Powersave exit mask
[46:47] */
#define SRR1_WS_DEEPEST 0x00030000 /* Some resources not
maintained,
* may not be recoverable */
diff --git a/arch/powerpc/kernel/idle_power7.S
b/arch/powerpc/kernel/idle_power7.S
index e11863f..c80bb4b 100644
--- a/arch/powerpc/kernel/idle_power7.S
+++ b/arch/powerpc/kernel/idle_power7.S
@@ -108,9 +108,7 @@ _GLOBAL(power7_wakeup_loss)
ld r5,_NIP(r1)
addi r1,r1,INT_FRAME_SIZE
mtcr r3
- mtspr SPRN_SRR1,r4
- mtspr SPRN_SRR0,r5
- rfid
+ b power7_wakeup_common
_GLOBAL(power7_wakeup_noloss)
lbz r0,PACA_NAPSTATELOST(r13)
@@ -120,6 +118,23 @@ _GLOBAL(power7_wakeup_noloss)
ld r4,_MSR(r1)
ld r5,_NIP(r1)
addi r1,r1,INT_FRAME_SIZE
- mtspr SPRN_SRR1,r4
+ /* Fall through */
+
+power7_wakeup_common:
+BEGIN_FTR_SECTION
+ mfspr r3,SPRN_SRR1
+ extrdi r3,r3,4,42 /* Extract SRR1_WAKEMASK */
+ cmpwi r3,SRR1_WAKEDBELLH >> SRR1_WAKESHIFT
+ beq 1f
+ cmpwi r3,SRR1_WAKEDBELLP >> SRR1_WAKESHIFT
+ bne 2f
+
+1: /* Woken by a doorbell, set doorbell happened in paca */
+ lbz r3,PACAIRQHAPPENED(r13)
+ ori r3,r3,PACA_IRQ_DBELL
+ stb r3,PACAIRQHAPPENED(r13)
+END_FTR_SECTION_IFSET(CPU_FTR_DBELL)
+
+2: mtspr SPRN_SRR1,r4
mtspr SPRN_SRR0,r5
rfid
--
1.7.10.4
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