linux-kernel - [PATCH 2/2] powerpc/powernv/idle: save-restore DAWR0,DAWRX0 for P10

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Message-Id: <20200703124640.42820-2-psampat@linux.ibm.com>
Date:   Fri,  3 Jul 2020 18:16:40 +0530
From:   Pratik Rajesh Sampat <psampat@...ux.ibm.com>
To:     mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, benh@...nel.crashing.org,
        paulus@...ba.org, ego@...ux.vnet.ibm.com, svaidy@...ux.ibm.com,
        psampat@...ux.ibm.com, pratik.r.sampat@...il.com
Subject: [PATCH 2/2] powerpc/powernv/idle: save-restore DAWR0,DAWRX0 for P10

Additional registers DAWR0, DAWRX0 may be lost on Power 10 for
stop levels < 4.
Therefore save the values of these SPRs before entering a  "stop"
state and restore their values on wakeup.

Signed-off-by: Pratik Rajesh Sampat <psampat@...ux.ibm.com>
---
 arch/powerpc/platforms/powernv/idle.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
index 19d94d021357..471d4a65b1fa 100644
--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -600,6 +600,8 @@ struct p9_sprs {
 	u64 iamr;
 	u64 amor;
 	u64 uamor;
+	u64 dawr0;
+	u64 dawrx0;
 };
 
 static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
@@ -677,6 +679,10 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
 		sprs.tscr	= mfspr(SPRN_TSCR);
 		if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))
 			sprs.ldbar = mfspr(SPRN_LDBAR);
+		if (cpu_has_feature(CPU_FTR_ARCH_31)) {
+			sprs.dawr0 = mfspr(SPRN_DAWR0);
+			sprs.dawrx0 = mfspr(SPRN_DAWRX0);
+		}
 
 		sprs_saved = true;
 
@@ -792,6 +798,10 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
 	mtspr(SPRN_MMCR2,	sprs.mmcr2);
 	if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))
 		mtspr(SPRN_LDBAR, sprs.ldbar);
+	if (cpu_has_feature(CPU_FTR_ARCH_31)) {
+		mtspr(SPRN_DAWR0, sprs.dawr0);
+		mtspr(SPRN_DAWRX0, sprs.dawrx0);
+	}
 
 	mtspr(SPRN_SPRG3,	local_paca->sprg_vdso);
 
-- 
2.25.4