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    Subject[PATCH 05/11] ARM: Introduce CPU_METHOD_OF_DECLARE() for cpu hotplug/smp
    Date
    The goal of multi-platform kernels is to remove the need for mach
    directories and machine descriptors. To further that goal,
    introduce CPU_METHOD_OF_DECLARE() to allow cpu hotplug/smp
    support to be separated from the machine descriptors.
    Implementers should specify an enable-method property in their
    cpus node and then implement a matching set of smp_ops in their
    hotplug/smp code, wiring it up with the CPU_METHOD_OF_DECLARE()
    macro. When the kernel is compiled we'll collect all the
    enable-method smp_ops into one section for use at boot.

    At boot time we'll look for an enable-method in each cpu node and
    try to match that against all known CPU enable methods in the
    kernel. If there are no enable-methods in the cpu nodes we
    fallback to the cpus node and try to use any enable-method found
    there. If that doesn't work we fall back to the old way of using
    the machine descriptor.

    Cc: Mark Rutland <mark.rutland@arm.com>
    Cc: Russell King <linux@arm.linux.org.uk>
    Cc: <devicetree@vger.kernel.org>
    Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
    ---
    arch/arm/include/asm/smp.h | 9 +++++++++
    arch/arm/kernel/devtree.c | 38 ++++++++++++++++++++++++++++++++++++++
    include/asm-generic/vmlinux.lds.h | 10 ++++++++++
    3 files changed, 57 insertions(+)

    diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h
    index a8cae71c..c27ec55 100644
    --- a/arch/arm/include/asm/smp.h
    +++ b/arch/arm/include/asm/smp.h
    @@ -112,6 +112,15 @@ struct smp_operations {
    #endif
    };

    +struct of_cpu_method {
    + const char *method;
    + struct smp_operations *ops;
    +};
    +
    +#define CPU_METHOD_OF_DECLARE(name, _method, _ops) \
    + static const struct of_cpu_method __cpu_method_of_table_##name \
    + __used __section(__cpu_method_of_table) \
    + = { .method = _method, .ops = _ops }
    /*
    * set platform specific SMP operations
    */
    diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c
    index f35906b..71a8592 100644
    --- a/arch/arm/kernel/devtree.c
    +++ b/arch/arm/kernel/devtree.c
    @@ -25,6 +25,7 @@
    #include <asm/smp_plat.h>
    #include <asm/mach/arch.h>
    #include <asm/mach-types.h>
    +#include <asm/smp.h>

    void __init early_init_dt_add_memory_arch(u64 base, u64 size)
    {
    @@ -63,6 +64,36 @@ void __init arm_dt_memblock_reserve(void)
    }
    }

    +#ifdef CONFIG_SMP
    +extern struct of_cpu_method __cpu_method_of_table[];
    +
    +static const struct of_cpu_method __cpu_method_of_table_sentinel
    + __used __section(__cpu_method_of_table_end);
    +
    +static int __init set_smp_ops_by_method(struct device_node *node)
    +{
    + const char *method;
    + struct of_cpu_method *m = __cpu_method_of_table;
    +
    + if (of_property_read_string(node, "enable-method", &method))
    + return 0;
    +
    + for (; m != &__cpu_method_of_table_sentinel; m++)
    + if (!strcmp(m->method, method)) {
    + smp_set_ops(m->ops);
    + return 1;
    + }
    +
    + return 0;
    +}
    +#else
    +static inline int set_smp_ops_by_method(struct device_node *node)
    +{
    + return 1;
    +}
    +#endif
    +
    +
    /*
    * arm_dt_init_cpu_maps - Function retrieves cpu nodes from the device tree
    * and builds the cpu logical map array containing MPIDR values related to
    @@ -79,6 +110,7 @@ void __init arm_dt_init_cpu_maps(void)
    * read as 0.
    */
    struct device_node *cpu, *cpus;
    + int found_method = 0;
    u32 i, j, cpuidx = 1;
    u32 mpidr = is_smp() ? read_cpuid_mpidr() & MPIDR_HWID_BITMASK : 0;

    @@ -150,8 +182,14 @@ void __init arm_dt_init_cpu_maps(void)
    }

    tmp_map[i] = hwid;
    +
    + if (!found_method)
    + found_method = set_smp_ops_by_method(cpu);
    }

    + if (!found_method)
    + set_smp_ops_by_method(cpus);
    +
    if (!bootcpu_valid) {
    pr_warn("DT missing boot CPU MPIDR[23:0], fall back to default cpu_logical_map\n");
    return;
    diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
    index 83e2c31..918b1b5 100644
    --- a/include/asm-generic/vmlinux.lds.h
    +++ b/include/asm-generic/vmlinux.lds.h
    @@ -167,6 +167,15 @@
    #define CLK_OF_TABLES()
    #endif

    +#ifdef CONFIG_SMP
    +#define CPU_METHOD_OF_TABLES() . = ALIGN(8); \
    + VMLINUX_SYMBOL(__cpu_method_of_table) = .; \
    + *(__cpu_method_of_table) \
    + *(__cpu_method_of_table_end)
    +#else
    +#define CPU_METHOD_OF_TABLES()
    +#endif
    +
    #define KERNEL_DTB() \
    STRUCT_ALIGN(); \
    VMLINUX_SYMBOL(__dtb_start) = .; \
    @@ -490,6 +499,7 @@
    MEM_DISCARD(init.rodata) \
    CLK_OF_TABLES() \
    CLKSRC_OF_TABLES() \
    + CPU_METHOD_OF_TABLES() \
    KERNEL_DTB() \
    IRQCHIP_OF_MATCH_TABLE()

    --
    The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
    hosted by The Linux Foundation


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