[Zesty][PATCH 08/13] powerpc/powernv: POWER9 support for msgsnd/doorbell IPI

[Gustavo Walbon]

From: Nicholas Piggin <npiggin at gmail.com>

POWER9 requires msgsync for receiver-side synchronization, and a DD1
workaround restricts IPIs to core-local.

Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
[mpe: Drop no longer needed asm feature macro changes]
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>

(cherry picked from commit 6b3edefefa6752df57ad636f26baa1b0a502ddab  in
linux-next)
Signed-off-by: Gustavo Walbon <gwalbon at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/dbell.h      |  3 +++
 arch/powerpc/include/asm/ppc-opcode.h |  2 ++
 arch/powerpc/platforms/powernv/smp.c  | 28 ++++++++++++++++++++++++++--
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/dbell.h b/arch/powerpc/include/asm/dbell.h
index 040944659a20..f70cbfe0ec04 100644
--- a/arch/powerpc/include/asm/dbell.h
+++ b/arch/powerpc/include/asm/dbell.h
@@ -51,6 +51,9 @@ static inline void ppc_msgsnd_sync(void)
 /* sync after taking message interrupt */
 static inline void ppc_msgsync(void)
 {
+	/* sync is not required when taking messages from the same core */
+	__asm__ __volatile__ (ASM_FTR_IFSET(PPC_MSGSYNC " ; lwsync", "", %0)
+				: : "i" (CPU_FTR_HVMODE|CPU_FTR_ARCH_300));
 }
 
 #else /* CONFIG_PPC_BOOK3S */
diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
index d99bd442aacb..9b7e9b9dee34 100644
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -161,6 +161,7 @@
 #define PPC_INST_MFTMR			0x7c0002dc
 #define PPC_INST_MSGSND			0x7c00019c
 #define PPC_INST_MSGCLR			0x7c0001dc
+#define PPC_INST_MSGSYNC		0x7c0006ec
 #define PPC_INST_MSGSNDP		0x7c00011c
 #define PPC_INST_MTTMR			0x7c0003dc
 #define PPC_INST_NOP			0x60000000
@@ -338,6 +339,7 @@
 					___PPC_RB(b) | __PPC_EH(eh))
 #define PPC_MSGSND(b)		stringify_in_c(.long PPC_INST_MSGSND | \
 					___PPC_RB(b))
+#define PPC_MSGSYNC		stringify_in_c(.long PPC_INST_MSGSYNC)
 #define PPC_MSGCLR(b)		stringify_in_c(.long PPC_INST_MSGCLR | \
 					___PPC_RB(b))
 #define PPC_MSGSNDP(b)		stringify_in_c(.long PPC_INST_MSGSNDP | \
diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c
index 80f5e2619632..3cd6af930744 100644
--- a/arch/powerpc/platforms/powernv/smp.c
+++ b/arch/powerpc/platforms/powernv/smp.c
@@ -270,6 +270,23 @@ static void pnv_cause_ipi(int cpu)
 	icp_ops->cause_ipi(cpu);
 }
 
+static void pnv_p9_dd1_cause_ipi(int cpu)
+{
+	int this_cpu = get_cpu();
+
+	/*
+	 * POWER9 DD1 has a global addressed msgsnd, but for now we restrict
+	 * IPIs to same core, because it requires additional synchronization
+	 * for inter-core doorbells which we do not implement.
+	 */
+	if (cpumask_test_cpu(cpu, cpu_sibling_mask(this_cpu)))
+		doorbell_global_ipi(cpu);
+	else
+		icp_ops->cause_ipi(cpu);
+
+	put_cpu();
+}
+
 static void __init pnv_smp_probe(void)
 {
 	if (xive_enabled())
@@ -277,8 +294,15 @@ static void __init pnv_smp_probe(void)
 	else
 		xics_smp_probe();
 
-	if (cpu_has_feature(CPU_FTR_DBELL) && !cpu_has_feature(CPU_FTR_ARCH_300)) {
-		smp_ops->cause_ipi = pnv_cause_ipi;
+	if (cpu_has_feature(CPU_FTR_DBELL)) {
+		if (cpu_has_feature(CPU_FTR_ARCH_300)) {
+			if (cpu_has_feature(CPU_FTR_POWER9_DD1))
+				smp_ops->cause_ipi = pnv_p9_dd1_cause_ipi;
+			else
+				smp_ops->cause_ipi = doorbell_global_ipi;
+		} else {
+			smp_ops->cause_ipi = pnv_cause_ipi;
+		}
 	} else {
 		smp_ops->cause_ipi = icp_ops->cause_ipi;
 	}
-- 
2.11.0