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LPCR_PECE1 bit controls whether decrementer interrupts are allowed to
cause exit from power-saving mode. While waking up from winkle, restoring
LPCR with LPCR_PECE1 set (i.e Decrementer interrupts allowed) can cause
issue in the following scenario:
- All the threads in a core are offlined. The core enters deep winkle.
- Spurious interrupt wakes up a thread in the core. Here LPCR is restored
with LPCR_PECE1 bit set.
- Since it was a spurious interrupt on a offline thread, the thread clears
the interrupt and goes back to winkle.
- Here before the thread executes winkle and puts the core into deep winkle,
if a decrementer interrupt occurs on any of the sibling threads in the core
that thread wakes up.
- Since in offline loop we are flushing interrupt only in case of external
interrupt, the decrementer interrupt does not get flushed. So at this stage
the thread is stuck in this is loop of waking up at 0x100 due to decrementer
interrupt, not flushing the interrupt as only external interrupts get flushed,
entering winkle, waking up at 0x100 again.
Fix this by programming PORE to restore LPCR with LPCR_PECE1 bit
cleared when waking up from winkle.
Signed-off-by: Shreyas B. Prabhu <shreyas@linux.vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
0eb13208aa