This patch enables POWER8 doorbell IPIs on powernv.
Since doorbells can only IPI within a core, we test to see when we can use
doorbells and if not we fall back to XICS. This also enables hypervisor
doorbells to wakeup us up from nap/sleep via the LPCR PECEDH bit.
Based on tests by Anton, the best case IPI latency between two threads dropped
from 894ns to 512ns.
Signed-off-by: Michael Neuling <mi...@neuling.org>
---
v2:
Adds select of PPC_DOORBELL for PSERIES and POWERNV as suggested by mpe.
diff --git a/arch/powerpc/kernel/cpu_setup_power.S
b/arch/powerpc/kernel/cpu_setup_power.S
index 1557e7c..4673353 100644
--- a/arch/powerpc/kernel/cpu_setup_power.S
+++ b/arch/powerpc/kernel/cpu_setup_power.S
@@ -56,6 +56,7 @@ _GLOBAL(__setup_cpu_power8)
li r0,0
mtspr SPRN_LPID,r0
mfspr r3,SPRN_LPCR
+ ori r3, r3, LPCR_PECEDH
bl __init_LPCR
bl __init_HFSCR
bl __init_tlb_power8
@@ -74,6 +75,7 @@ _GLOBAL(__restore_cpu_power8)
li r0,0
mtspr SPRN_LPID,r0
mfspr r3,SPRN_LPCR
+ ori r3, r3, LPCR_PECEDH
bl __init_LPCR
bl __init_HFSCR
bl __init_tlb_power8
diff --git a/arch/powerpc/platforms/powernv/Kconfig
b/arch/powerpc/platforms/powernv/Kconfig
index c252ee9..45a8ed0 100644
--- a/arch/powerpc/platforms/powernv/Kconfig
+++ b/arch/powerpc/platforms/powernv/Kconfig
@@ -17,6 +17,7 @@ config PPC_POWERNV
select CPU_FREQ_GOV_USERSPACE
select CPU_FREQ_GOV_ONDEMAND
select CPU_FREQ_GOV_CONSERVATIVE
+ select PPC_DOORBELL
default y
config PPC_POWERNV_RTAS
diff --git a/arch/powerpc/platforms/powernv/smp.c
b/arch/powerpc/platforms/powernv/smp.c
index 0062a43..5fcfcf4 100644
--- a/arch/powerpc/platforms/powernv/smp.c
+++ b/arch/powerpc/platforms/powernv/smp.c
@@ -32,6 +32,7 @@
#include <asm/opal.h>
#include <asm/runlatch.h>
#include <asm/code-patching.h>
+#include <asm/dbell.h>
#include "powernv.h"
@@ -46,6 +47,11 @@ static void pnv_smp_setup_cpu(int cpu)
{
if (cpu != boot_cpuid)
xics_setup_cpu();
+
+#ifdef CONFIG_PPC_DOORBELL
+ if (cpu_has_feature(CPU_FTR_DBELL))
+ doorbell_setup_this_cpu();
+#endif
}
int pnv_smp_kick_cpu(int nr)
diff --git a/arch/powerpc/platforms/pseries/Kconfig
b/arch/powerpc/platforms/pseries/Kconfig
index 2cb8b77..756b482 100644
--- a/arch/powerpc/platforms/pseries/Kconfig
+++ b/arch/powerpc/platforms/pseries/Kconfig
@@ -21,6 +21,7 @@ config PPC_PSERIES
select HAVE_CONTEXT_TRACKING
select HOTPLUG_CPU if SMP
select ARCH_RANDOM
+ select PPC_DOORBELL
default y
config PPC_SPLPAR
diff --git a/arch/powerpc/sysdev/xics/icp-native.c
b/arch/powerpc/sysdev/xics/icp-native.c
index 9dee470..de8d948 100644
--- a/arch/powerpc/sysdev/xics/icp-native.c
+++ b/arch/powerpc/sysdev/xics/icp-native.c
@@ -26,6 +26,7 @@
#include <asm/errno.h>
#include <asm/xics.h>
#include <asm/kvm_ppc.h>
+#include <asm/dbell.h>
struct icp_ipl {
union {
@@ -145,7 +146,13 @@ static unsigned int icp_native_get_irq(void)
static void icp_native_cause_ipi(int cpu, unsigned long data)
{
kvmppc_set_host_ipi(cpu, 1);
- icp_native_set_qirr(cpu, IPI_PRIORITY);
+#ifdef CONFIG_PPC_DOORBELL
+ if (cpu_has_feature(CPU_FTR_DBELL) &&
+ (cpumask_test_cpu(cpu, cpu_sibling_mask(smp_processor_id()))))
+ doorbell_cause_ipi(cpu, data);
+ else
+#endif
+ icp_native_set_qirr(cpu, IPI_PRIORITY);
}
void xics_wake_cpu(int cpu)
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