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ARM: Introduce CPU_METHOD_OF_DECLARE() for cpu hotplug/smp

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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: 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>
Signed-off-by: Kumar Gala <galak@codeaurora.org>
This commit is contained in:
Stephen Boyd 2013-10-30 18:21:09 -07:00 • committed by Kumar Gala
parent cf1e8f0cd6
commit 6c3ff8b11a
3 changed files with 59 additions and 0 deletions
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40
arch/arm/kernel/devtree.c
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@ -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;