[PATCH v2 2/2] powerpc/64s: idle skip POWER9 DD1 and DD2.0 specific workarounds on DD2.1

[Nicholas Piggin]

DD2.1 does not have to flush the ERAT after a state-loss idle. It also
does not have to save and restore MMCR0 (although it does have to save
restore in deep idle states, like other PMU registers).

Performance testing was done on a DD2.1 using only the stop0 idle state
(the shallowest state which supports state loss), using context_switch
selftest configured to ping-poing between two threads on the same core
and two different cores.

Performance improvement for same core is 7.0%, different cores is 14.8%.

Reviewed-by: Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
---
 arch/powerpc/kernel/idle_book3s.S | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 175d49f468af..59657783d1d5 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -112,12 +112,14 @@ power9_save_additional_sprs:
 	std	r4, STOP_HFSCR(r13)
 
 	mfspr	r3, SPRN_MMCRA
-	mfspr	r4, SPRN_MMCR1
+	mfspr	r4, SPRN_MMCR0
 	std	r3, STOP_MMCRA(r13)
-	std	r4, STOP_MMCR1(r13)
+	std	r4, _MMCR0(r1)
 
-	mfspr	r3, SPRN_MMCR2
-	std	r3, STOP_MMCR2(r13)
+	mfspr	r3, SPRN_MMCR1
+	mfspr	r4, SPRN_MMCR2
+	std	r3, STOP_MMCR1(r13)
+	std	r4, STOP_MMCR2(r13)
 	blr
 
 power9_restore_additional_sprs:
@@ -135,11 +137,14 @@ power9_restore_additional_sprs:
 	ld	r4, STOP_MMCRA(r13)
 	mtspr	SPRN_HFSCR, r3
 	mtspr	SPRN_MMCRA, r4
-	/* We have already restored PACA_MMCR0 */
-	ld	r3, STOP_MMCR1(r13)
-	ld	r4, STOP_MMCR2(r13)
-	mtspr	SPRN_MMCR1, r3
-	mtspr	SPRN_MMCR2, r4
+
+	ld	r3, _MMCR0(r1)
+	ld	r4, STOP_MMCR1(r13)
+	mtspr	SPRN_MMCR0, r3
+	mtspr	SPRN_MMCR1, r4
+
+	ld	r3, STOP_MMCR2(r13)
+	mtspr	SPRN_MMCR2, r3
 	blr
 
 /*
@@ -350,6 +355,7 @@ power_enter_stop:
 	b 	pnv_wakeup_noloss
 
 .Lhandle_esl_ec_set:
+BEGIN_FTR_SECTION
 	/*
 	 * POWER9 DD2 can incorrectly set PMAO when waking up after a
 	 * state-loss idle. Saving and restoring MMCR0 over idle is a
@@ -357,6 +363,7 @@ power_enter_stop:
 	 */
 	mfspr	r4,SPRN_MMCR0
 	std	r4,_MMCR0(r1)
+END_FTR_SECTION_IFSET(CPU_FTR_POWER9_DD1 | CPU_FTR_POWER9_DD20)
 
 /*
  * Check if the requested state is a deep idle state.
@@ -542,15 +549,17 @@ pnv_restore_hyp_resource_arch300:
 	 * then clear bit 60 in MMCRA to ensure the PMU starts running.
 	 */
 	blt	cr3,1f
+BEGIN_FTR_SECTION
 	PPC_INVALIDATE_ERAT
 	ld	r1,PACAR1(r13)
+	ld	r4,_MMCR0(r1)
+	mtspr	SPRN_MMCR0,r4
+END_FTR_SECTION_IFSET(CPU_FTR_POWER9_DD1 | CPU_FTR_POWER9_DD20)
 	mfspr	r4,SPRN_MMCRA
 	ori	r4,r4,(1 << (63-60))
 	mtspr	SPRN_MMCRA,r4
 	xori	r4,r4,(1 << (63-60))
 	mtspr	SPRN_MMCRA,r4
-	ld	r4,_MMCR0(r1)
-	mtspr	SPRN_MMCR0,r4
 1:
 	/*
 	 * POWER ISA 3. Use PSSCR to determine if we
-- 
2.15.0