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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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