arm64: enable generic clockevent broadcast

On platforms with power management capabilities, timers that are shut
down when a CPU enters deep C-states must be emulated using an always-on
timer and a timer IPI to relay the timer IRQ to target CPUs on an SMP
system.

This patch enables the generic clockevents broadcast infrastructure for
arm64, by providing the required Kconfig entries and adding the timer
IPI infrastructure.

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

3 files changed, 20 insertions, 1 deletions

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6d4dd22ee4b7..baab4eb8bfe4 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2,6 +2,7 @@ config ARM64
         def_bool y
         select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
         select ARCH_USE_CMPXCHG_LOCKREF
+        select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
         select ARCH_WANT_OPTIONAL_GPIOLIB
         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
         select ARCH_WANT_FRAME_POINTERS
@@ -12,6 +13,7 @@ config ARM64
         select CLONE_BACKWARDS
         select COMMON_CLK
         select GENERIC_CLOCKEVENTS
+        select GENERIC_CLOCKEVENTS_BROADCAST if SMP
         select GENERIC_IOMAP
         select GENERIC_IRQ_PROBE
         select GENERIC_IRQ_SHOW
diff --git a/arch/arm64/include/asm/hardirq.h b/arch/arm64/include/asm/hardirq.h
index 990c051e7829..ae4801d77514 100644
--- a/arch/arm64/include/asm/hardirq.h
+++ b/arch/arm64/include/asm/hardirq.h
@@ -20,7 +20,7 @@
 #include <linux/threads.h>
 #include <asm/irq.h>
 
-#define NR_IPI  4
+#define NR_IPI  5
 
 typedef struct {
         unsigned int __softirq_pending;
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index a0c2ca602cf8..0b8c859e744f 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -61,6 +61,7 @@ enum ipi_msg_type {
         IPI_CALL_FUNC,
         IPI_CALL_FUNC_SINGLE,
         IPI_CPU_STOP,
+        IPI_TIMER,
 };
 
 /*
@@ -447,6 +448,7 @@ static const char *ipi_types[NR_IPI] = {
         S(IPI_CALL_FUNC, "Function call interrupts"),
         S(IPI_CALL_FUNC_SINGLE, "Single function call interrupts"),
         S(IPI_CPU_STOP, "CPU stop interrupts"),
+        S(IPI_TIMER, "Timer broadcast interrupts"),
 };
 
 void show_ipi_list(struct seq_file *p, int prec)
@@ -532,6 +534,14 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
                 irq_exit();
                 break;
 
+#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
+        case IPI_TIMER:
+                irq_enter();
+                tick_receive_broadcast();
+                irq_exit();
+                break;
+#endif
+
         default:
                 pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu, ipinr);
                 break;
@@ -544,6 +554,13 @@ void smp_send_reschedule(int cpu)
         smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
 }
 
+#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
+void tick_broadcast(const struct cpumask *mask)
+{
+        smp_cross_call(mask, IPI_TIMER);
+}
+#endif
+
 void smp_send_stop(void)
 {
         unsigned long timeout;