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@xxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
Cc: <devicetree@xxxxxxxxxxxxxxx>
Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
---
arch/arm/include/asm/smp.h | 9 +++++++++
arch/arm/kernel/devtree.c | 40 +++++++++++++++++++++++++++++++++++++++
include/asm-generic/vmlinux.lds.h | 10 ++++++++++
3 files changed, 59 insertions(+)
diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h
index 22a3b9b..772435b 100644
--- a/arch/arm/include/asm/smp.h
+++ b/arch/arm/include/asm/smp.h
@@ -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
*/
diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c
index 739c3df..91cc3f8 100644
--- a/arch/arm/kernel/devtree.c
+++ b/arch/arm/kernel/devtree.c
@@ -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;
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index bc2121f..bd02ca7 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_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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