linux-kernel - [PATCH v2 2/3] powerpc/powernv/idle: save-restore DAWR0,DAWRX0 for P10

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Date:   Fri, 10 Jul 2020 10:52:06 +0530
From:   Pratik Rajesh Sampat <psampat@...ux.ibm.com>
To:     mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
        mikey@...ling.org, ravi.bangoria@...ux.ibm.com,
        ego@...ux.vnet.ibm.com, svaidy@...ux.ibm.com,
        psampat@...ux.ibm.com, pratik.r.sampat@...il.com,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/3] 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..f2e2a6a4c274 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)
@@ -687,6 +689,10 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
 	sprs.iamr	= mfspr(SPRN_IAMR);
 	sprs.amor	= mfspr(SPRN_AMOR);
 	sprs.uamor	= mfspr(SPRN_UAMOR);
+	if (cpu_has_feature(CPU_FTR_ARCH_31)) {
+		sprs.dawr0 = mfspr(SPRN_DAWR0);
+		sprs.dawrx0 = mfspr(SPRN_DAWRX0);
+	}
 
 	srr1 = isa300_idle_stop_mayloss(psscr);		/* go idle */
 
@@ -710,6 +716,10 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
 		mtspr(SPRN_IAMR,	sprs.iamr);
 		mtspr(SPRN_AMOR,	sprs.amor);
 		mtspr(SPRN_UAMOR,	sprs.uamor);
+		if (cpu_has_feature(CPU_FTR_ARCH_31)) {
+			mtspr(SPRN_DAWR0, sprs.dawr0);
+			mtspr(SPRN_DAWRX0, sprs.dawrx0);
+		}
 
 		/*
 		 * Workaround for POWER9 DD2.0, if we lost resources, the ERAT
-- 
2.25.4