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| author | Akshay Adiga <akshay.adiga@linux.vnet.ibm.com> | 2017-06-28 06:46:49 +0530 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2017-06-28 22:46:06 +1000 |
| commit | 4d0d7c02df680740da41f5f92a238c35796ca5be (patch) | |
| tree | 7d364419a6b427cd485e66e5211cabc63dfeafba /arch/powerpc/kernel/idle_book3s.S | |
| parent | 39e46751839dfe4c34eb354eee1e278082fc9d07 (diff) | |
| download | lwn-4d0d7c02df680740da41f5f92a238c35796ca5be.tar.gz lwn-4d0d7c02df680740da41f5f92a238c35796ca5be.zip | |
powerpc/powernv/idle: Clear r12 on wakeup from stop lite
pnv_wakeup_noloss() expects r12 to contain SRR1 value to determine if the wakeup
reason is an HMI in CHECK_HMI_INTERRUPT.
When we wakeup with ESL=0, SRR1 will not contain the wakeup reason, so there is
no point setting r12 to SRR1.
However, we don't set r12 at all so r12 contains garbage (likely a kernel
pointer), and is still used to check HMI assuming that it contained SRR1. This
causes the OPAL msglog to be filled with the following print:
HMI: Received HMI interrupt: HMER = 0x0040000000000000
This patch clears r12 after waking up from stop with ESL=EC=0, so that we don't
accidentally enter the HMI handler in pnv_wakeup_noloss() if the value of
r12[42:45] corresponds to HMI as wakeup reason.
Prior to commit 9d29250136f6 ("powerpc/64s/idle: Avoid SRR usage in idle
sleep/wake paths") this bug existed, in that we would incorrectly look at SRR1
to check for a HMI when SRR1 didn't contain a wakeup reason. However the SRR1
value would just happen to never have bits 42:45 set.
Fixes: 9d29250136f6 ("powerpc/64s/idle: Avoid SRR usage in idle sleep/wake paths")
Signed-off-by: Akshay Adiga <akshay.adiga@linux.vnet.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Change log and comment massaging]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel/idle_book3s.S')
| -rw-r--r-- | arch/powerpc/kernel/idle_book3s.S | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S index f6518c768d2a..5adb390e773b 100644 --- a/arch/powerpc/kernel/idle_book3s.S +++ b/arch/powerpc/kernel/idle_book3s.S @@ -256,6 +256,19 @@ power_enter_stop: bne .Lhandle_esl_ec_set IDLE_STATE_ENTER_SEQ(PPC_STOP) li r3,0 /* Since we didn't lose state, return 0 */ + + /* + * pnv_wakeup_noloss() expects r12 to contain the SRR1 value so + * it can determine if the wakeup reason is an HMI in + * CHECK_HMI_INTERRUPT. + * + * However, when we wakeup with ESL=0, SRR1 will not contain the wakeup + * reason, so there is no point setting r12 to SRR1. + * + * Further, we clear r12 here, so that we don't accidentally enter the + * HMI in pnv_wakeup_noloss() if the value of r12[42:45] == WAKE_HMI. + */ + li r12, 0 b pnv_wakeup_noloss .Lhandle_esl_ec_set: |