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Subject[PATCH v1 2/6] arm: smp: Introduce a non-maskable IPI
Date
This patch introduces a new IPI intended to be routed to FIQ rather
than IRQ. An IPI based upon FIQ can be used to implement debug
features that require non-maskable interrupts.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Russell King <linux@arm.linux.org.uk>
---
arch/arm/include/asm/hardirq.h | 2 +-
arch/arm/include/asm/smp.h | 3 +++
arch/arm/kernel/smp.c | 7 +++++++
3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/hardirq.h b/arch/arm/include/asm/hardirq.h
index fe3ea77..5df33e3 100644
--- 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 8
+#define NR_IPI 9

typedef struct {
unsigned int __softirq_pending;
diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h
index 2ec765c..0e23384 100644
--- a/arch/arm/include/asm/smp.h
+++ b/arch/arm/include/asm/smp.h
@@ -20,6 +20,9 @@

#define raw_smp_processor_id() (current_thread_info()->cpu)

+/* bitmap of IPIs that must be signalled using FIQ */
+#define SMP_IPI_FIQ_MASK 0x0100
+
struct seq_file;

/*
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 9388a3d..b2404d0 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -72,6 +72,7 @@ enum ipi_msg_type {
IPI_CPU_STOP,
IPI_IRQ_WORK,
IPI_COMPLETION,
+ IPI_FIQ,
};

static DECLARE_COMPLETION(cpu_running);
@@ -451,6 +452,7 @@ static const char *ipi_types[NR_IPI] __tracepoint_string = {
S(IPI_CPU_STOP, "CPU stop interrupts"),
S(IPI_IRQ_WORK, "IRQ work interrupts"),
S(IPI_COMPLETION, "completion interrupts"),
+ S(IPI_FIQ, "FIQ interrupts"),
};

static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
@@ -618,6 +620,11 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
irq_exit();
break;

+ case IPI_FIQ:
+ BUILD_BUG_ON(SMP_IPI_FIQ_MASK != BIT(IPI_FIQ));
+ pr_warn("CPU%u: IPI FIQ delivered via IRQ vector\n", cpu);
+ break;
+
default:
printk(KERN_CRIT "CPU%u: Unknown IPI message 0x%x\n",
cpu, ipinr);
--
1.9.3


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