Commit 6c3ff8b1 authored by Stephen Boyd's avatar Stephen Boyd Committed by Kumar Gala
Browse files

ARM: Introduce CPU_METHOD_OF_DECLARE() for cpu hotplug/smp 



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.

Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: <devicetree@vger.kernel.org>
Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: default avatarKumar Gala <galak@codeaurora.org>
parent cf1e8f0c

arch/arm/include/asm/smp.h

+9 −0
Original line number Diff line number Diff line
@@ -114,6 +114,15 @@ 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

 */

arch/arm/kernel/devtree.c

+40 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <linux/of_fdt.h>

#include <linux/of_irq.h>

#include <linux/of_platform.h>

#include <linux/smp.h>



#include <asm/cputype.h>

#include <asm/setup.h>
@@ -63,6 +64,34 @@ void __init arm_dt_memblock_reserve(void) 
	}

}



#ifdef CONFIG_SMP

extern struct of_cpu_method __cpu_method_of_table_begin[];

extern struct of_cpu_method __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_begin;



	if (of_property_read_string(node, "enable-method", &method))

		return 0;



	for (; m < __cpu_method_of_table_end; 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 +108,7 @@ 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 +180,18 @@ void __init arm_dt_init_cpu_maps(void) 
		}



		tmp_map[i] = hwid;



		if (!found_method)

			found_method = set_smp_ops_by_method(cpu);

	}



	/*

	 * Fallback to an enable-method in the cpus node if nothing found in

	 * a cpu node.

	 */

	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;

include/asm-generic/vmlinux.lds.h

+10 −0
Original line number Diff line number Diff line
@@ -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_begin) = .; \

			   *(__cpu_method_of_table)			    \

			   VMLINUX_SYMBOL(__cpu_method_of_table_end) = .;

#else

#define CPU_METHOD_OF_TABLES()

#endif



#define KERNEL_DTB()							\

	STRUCT_ALIGN();							\

	VMLINUX_SYMBOL(__dtb_start) = .;				\
@@ -491,6 +500,7 @@ 
	MEM_DISCARD(init.rodata)					\

	CLK_OF_TABLES()							\

	CLKSRC_OF_TABLES()						\

	CPU_METHOD_OF_TABLES()						\

	KERNEL_DTB()							\

	IRQCHIP_OF_MATCH_TABLE()

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