powerpc: Avoid extra indirect function call in sending IPIs

On many platforms (including pSeries), smp_ops->message_pass is always
smp_muxed_ipi_message_pass.  This changes arch/powerpc/kernel/smp.c so
that if smp_ops->message_pass is NULL, it calls smp_muxed_ipi_message_pass
directly.

This means that a platform doesn't need to set both .message_pass and
.cause_ipi, only one of them.  It is a slight performance improvement
in that it gets rid of an indirect function call at the expense of a
predictable conditional branch.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

6 files changed, 19 insertions, 9 deletions

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 8ebc6700b98..2975f64cf31 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -238,15 +238,25 @@ irqreturn_t smp_ipi_demux(void)
 }
 #endif /* CONFIG_PPC_SMP_MUXED_IPI */
 
+static inline void do_message_pass(int cpu, int msg)
+{
+        if (smp_ops->message_pass)
+                smp_ops->message_pass(cpu, msg);
+#ifdef CONFIG_PPC_SMP_MUXED_IPI
+        else
+                smp_muxed_ipi_message_pass(cpu, msg);
+#endif
+}
+
 void smp_send_reschedule(int cpu)
 {
         if (likely(smp_ops))
-                smp_ops->message_pass(cpu, PPC_MSG_RESCHEDULE);
+                do_message_pass(cpu, PPC_MSG_RESCHEDULE);
 }
 
 void arch_send_call_function_single_ipi(int cpu)
 {
-        smp_ops->message_pass(cpu, PPC_MSG_CALL_FUNC_SINGLE);
+        do_message_pass(cpu, PPC_MSG_CALL_FUNC_SINGLE);
 }
 
 void arch_send_call_function_ipi_mask(const struct cpumask *mask)
@@ -254,7 +264,7 @@ void arch_send_call_function_ipi_mask(const struct cpumask *mask)
         unsigned int cpu;
 
         for_each_cpu(cpu, mask)
-                smp_ops->message_pass(cpu, PPC_MSG_CALL_FUNCTION);
+                do_message_pass(cpu, PPC_MSG_CALL_FUNCTION);
 }
 
 #if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC)
@@ -268,7 +278,7 @@ void smp_send_debugger_break(void)
 
         for_each_online_cpu(cpu)
                 if (cpu != me)
-                        smp_ops->message_pass(cpu, PPC_MSG_DEBUGGER_BREAK);
+                        do_message_pass(cpu, PPC_MSG_DEBUGGER_BREAK);
 }
 #endif
 
diff --git a/arch/powerpc/platforms/85xx/smp.c b/arch/powerpc/platforms/85xx/smp.c
index d6a93a10c0f..8eef8d2b447 100644
--- a/arch/powerpc/platforms/85xx/smp.c
+++ b/arch/powerpc/platforms/85xx/smp.c
@@ -236,7 +236,7 @@ void __init mpc85xx_smp_init(void)
         }
 
         if (cpu_has_feature(CPU_FTR_DBELL)) {
-                smp_85xx_ops.message_pass = smp_muxed_ipi_message_pass;
+                /* .message_pass defaults to smp_muxed_ipi_message_pass */
                 smp_85xx_ops.cause_ipi = doorbell_cause_ipi;
         }
 
diff --git a/arch/powerpc/platforms/iseries/smp.c b/arch/powerpc/platforms/iseries/smp.c
index e3265adde5d..2df48c2287b 100644
--- a/arch/powerpc/platforms/iseries/smp.c
+++ b/arch/powerpc/platforms/iseries/smp.c
@@ -75,7 +75,7 @@ static void __devinit smp_iSeries_setup_cpu(int nr)
 }
 
 static struct smp_ops_t iSeries_smp_ops = {
-        .message_pass = smp_muxed_ipi_message_pass,
+        .message_pass = NULL,   /* Use smp_muxed_ipi_message_pass */
         .cause_ipi    = smp_iSeries_cause_ipi,
         .probe        = smp_iSeries_probe,
         .kick_cpu     = smp_iSeries_kick_cpu,
diff --git a/arch/powerpc/platforms/powermac/smp.c b/arch/powerpc/platforms/powermac/smp.c
index db092d7c4c5..d15fca32297 100644
--- a/arch/powerpc/platforms/powermac/smp.c
+++ b/arch/powerpc/platforms/powermac/smp.c
@@ -447,7 +447,7 @@ void __init smp_psurge_give_timebase(void)
 
 /* PowerSurge-style Macs */
 struct smp_ops_t psurge_smp_ops = {
-        .message_pass   = smp_muxed_ipi_message_pass,
+        .message_pass   = NULL, /* Use smp_muxed_ipi_message_pass */
         .cause_ipi      = smp_psurge_cause_ipi,
         .probe          = smp_psurge_probe,
         .kick_cpu       = smp_psurge_kick_cpu,
diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c
index fbffd7e47ab..84dafd33edc 100644
--- a/arch/powerpc/platforms/pseries/smp.c
+++ b/arch/powerpc/platforms/pseries/smp.c
@@ -207,7 +207,7 @@ static struct smp_ops_t pSeries_mpic_smp_ops = {
 };
 
 static struct smp_ops_t pSeries_xics_smp_ops = {
-        .message_pass   = smp_muxed_ipi_message_pass,
+        .message_pass   = NULL, /* Use smp_muxed_ipi_message_pass */
         .cause_ipi      = NULL, /* Filled at runtime by xics_smp_probe() */
         .probe          = xics_smp_probe,
         .kick_cpu       = smp_pSeries_kick_cpu,
diff --git a/arch/powerpc/platforms/wsp/smp.c b/arch/powerpc/platforms/wsp/smp.c
index 9d20fa9d371..71bd105f386 100644
--- a/arch/powerpc/platforms/wsp/smp.c
+++ b/arch/powerpc/platforms/wsp/smp.c
@@ -75,7 +75,7 @@ static int __init smp_a2_probe(void)
 }
 
 static struct smp_ops_t a2_smp_ops = {
-        .message_pass   = smp_muxed_ipi_message_pass,
+        .message_pass   = NULL, /* Use smp_muxed_ipi_message_pass */
         .cause_ipi      = doorbell_cause_ipi,
         .probe          = smp_a2_probe,
         .kick_cpu       = smp_a2_kick_cpu,