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

From: Nicholas Piggin <[email-masked]>
Date: Fri, 20 Oct 2017 14:54:44 +1000

DD2.1 does not have to flush the ERAT after a state-loss idle. It also
does not have to save and restore MMCR0.

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%.

Cc: Vaidyanathan Srinivasan <[email-masked]>
Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/kernel/idle_book3s.S | 39 ++++++++++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 1125c9be9e06..3531a3e727d2 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
 
 /*
@@ -357,6 +362,7 @@ 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
@@ -364,6 +370,10 @@ power_enter_stop:
 	 */
 	mfspr	r4,SPRN_MMCR0
 	std	r4,_MMCR0(r1)
+FTR_SECTION_ELSE
+	nop
+	nop
+ALT_FTR_SECTION_END_IFCLR(CPU_FTR_POWER9_DD1 | CPU_FTR_POWER9_DD20)
 
 /*
  * Check if the requested state is a deep idle state.
@@ -555,15 +565,22 @@ pnv_restore_hyp_resource_arch300:
 	 * then clear bit 60 in MMCRA to ensure the PMU starts running.
 	 */
 	blt	cr3,1f
+BEGIN_FTR_SECTION
+	nop
+	nop
+	nop
+	nop
+FTR_SECTION_ELSE
 	PPC_INVALIDATE_ERAT
 	ld	r1,PACAR1(r13)
+	ld	r4,_MMCR0(r1)
+	mtspr	SPRN_MMCR0,r4
+ALT_FTR_SECTION_END_IFCLR(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
-- 
2.13.3