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powernv/powerpc: Add winkle support for offline cpus

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Winkle is a deep idle state supported in power8 chips. A core enters
winkle when all the threads of the core enter winkle. In this state
power supply to the entire chiplet i.e core, private L2 and private L3
is turned off. As a result it gives higher powersavings compared to
sleep.

But entering winkle results in a total hypervisor state loss. Hence the
hypervisor context has to be preserved before entering winkle and
restored upon wake up.

Power-on Reset Engine (PORE) is a dedicated engine which is responsible
for powering on the chiplet during wake up. It can be programmed to
restore the register contests of a few specific registers. This patch
uses PORE to restore register state wherever possible and uses stack to
save and restore rest of the necessary registers.

With hypervisor state restore things fall under three categories-
per-core state, per-subcore state and per-thread state. To manage this,
extend the infrastructure introduced for sleep. Mainly we add a paca
variable subcore_sibling_mask. Using this and the core_idle_state we can
distingush first thread in core and subcore.

Signed-off-by: Shreyas B. Prabhu <shreyas@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Shreyas B. Prabhu
2014-12-10 00:26:53 +05:30
committed by Michael Ellerman
parent 7cba160ad7
commit 77b54e9f21
13 changed files with 281 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
arch/powerpc/kernel/exceptions-64s.S
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@@ -102,9 +102,7 @@ system_reset_pSeries:
#ifdef CONFIG_PPC_P7_NAP
BEGIN_FTR_SECTION
/* Running native on arch 2.06 or later, check if we are
* waking up from nap. We only handle no state loss and
* supervisor state loss. We do -not- handle hypervisor
* state loss at this time.
* waking up from nap/sleep/winkle.
*/
mfspr r13,SPRN_SRR1
rlwinm. r13,r13,47-31,30,31
@@ -112,7 +110,16 @@ BEGIN_FTR_SECTION
cmpwi cr3,r13,2
/*
* Check if last bit of HSPGR0 is set. This indicates whether we are
* waking up from winkle.
*/
GET_PACA(r13)
clrldi r5,r13,63
clrrdi r13,r13,1
cmpwi cr4,r5,1
mtspr SPRN_HSPRG0,r13
lbz r0,PACA_THREAD_IDLE_STATE(r13)
cmpwi cr2,r0,PNV_THREAD_NAP
bgt cr2,8f /* Either sleep or Winkle */