ARM: SMP: basic IPI triggered completion support

We need a mechanism to let an inbound CPU signal that it is alive before
even getting into the kernel environment i.e. from early assembly code.
Using an IPI is the simplest way to achieve that.

This adds some basic infrastructure to register a struct completion
pointer to be "completed" when the dedicated IPI for this task is
received.

Signed-off-by: Nicolas Pitre <nico@linaro.org>

diff --git a/arch/arm/include/asm/hardirq.h b/arch/arm/include/asm/hardirq.h
index 2740c2a2df639361617f6fe484ead14f8625eaf2..3d7351c844aac0ae2392d441796ce9904dcaf717 100644 (file)
--- a/arch/arm/include/asm/hardirq.h
+++ b/arch/arm/include/asm/hardirq.h
@@ -5,7 +5,7 @@
 #include <linux/threads.h>
 #include <asm/irq.h>
 
-#define NR_IPI 6
+#define NR_IPI 7
 
 typedef struct {
        unsigned int __softirq_pending;

diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h
index a8cae71caceb3fb89c1ec949063b7a0d621dbdca..22a3b9b5d4a16fd4ece50bdfc83859f6ea38352f 100644 (file)
--- a/arch/arm/include/asm/smp.h
+++ b/arch/arm/include/asm/smp.h
@@ -84,6 +84,8 @@ extern void arch_send_call_function_single_ipi(int cpu);
 extern void arch_send_call_function_ipi_mask(const struct cpumask *mask);
 extern void arch_send_wakeup_ipi_mask(const struct cpumask *mask);
 
+extern int register_ipi_completion(struct completion *completion, int cpu);
+
 struct smp_operations {
 #ifdef CONFIG_SMP
        /*

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 72024ea8a3a6c07038103e153527cb2454e4552f..7d80a549cae5d6f74170e4e169f66a8dda6ef749 100644 (file)
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -66,6 +66,7 @@ enum ipi_msg_type {
        IPI_CALL_FUNC,
        IPI_CALL_FUNC_SINGLE,
        IPI_CPU_STOP,
+       IPI_COMPLETION,
 };
 
 static DECLARE_COMPLETION(cpu_running);
@@ -456,6 +457,7 @@ 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_COMPLETION, "completion interrupts"),
 };
 
 void show_ipi_list(struct seq_file *p, int prec)
@@ -515,6 +517,19 @@ static void ipi_cpu_stop(unsigned int cpu)
                cpu_relax();
 }
 
+static DEFINE_PER_CPU(struct completion *, cpu_completion);
+
+int register_ipi_completion(struct completion *completion, int cpu)
+{
+       per_cpu(cpu_completion, cpu) = completion;
+       return IPI_COMPLETION;
+}
+
+static void ipi_complete(unsigned int cpu)
+{
+       complete(per_cpu(cpu_completion, cpu));
+}
+
 /*
  * Main handler for inter-processor interrupts
  */
@@ -565,6 +580,12 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
                irq_exit();
                break;
 
+       case IPI_COMPLETION:
+               irq_enter();
+               ipi_complete(cpu);
+               irq_exit();
+               break;
+
        default:
                printk(KERN_CRIT "CPU%u: Unknown IPI message 0x%x\n",
                       cpu, ipinr);