The CPU_METHOD_OF_DECLARE() macro allows methods for assigning
SMP/hotplug operations to CPUS to be defined using device tree,
without the need for machine-dependent code.

And although it allows the *method* to be specified, it does *not*
allow any parameterization of that method.  For example, there is no
efficient way to define a machine-specific address or other
property one might want to define for secondary CPUs.

Define a new of_cpu_method->setup() function, which (if defined) is
called for nodes found having a matching "enable-method" property.
The matching node is supplied as the function's argument, allowing
additional required information to be extracted from that node.
A new macro CPU_METHOD_OF_DECLARE_SETUP() allows a setup method
to be supplied when a method is declared.

Extend the interface for set_smp_ops_by_method() so that it can
return a negative error code to allow DT parsing errors to be
reported by the setup function.

(Note that only the first "cpu" (or "cpus") node having a matching
method is used by set_smp_ops_by_method(); this logic is not
changed.)

Signed-off-by: Alex Elder <el...@linaro.org>
---
 arch/arm/include/asm/smp.h |   10 ++++++++--
 arch/arm/kernel/devtree.c  |   31 +++++++++++++++++++++++++------
 2 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h
index 2ec765c..ab4a5a9 100644
--- a/arch/arm/include/asm/smp.h
+++ b/arch/arm/include/asm/smp.h
@@ -115,15 +115,21 @@ struct smp_operations {
 #endif
 };
 
+struct device_node;
 struct of_cpu_method {
        const char *method;
+       int (*setup)(struct device_node *node);
        struct smp_operations *ops;
 };
 
-#define CPU_METHOD_OF_DECLARE(name, _method, _ops)                     \
+#define CPU_METHOD_OF_DECLARE_SETUP(name, _method, _setup, _ops)       \
        static const struct of_cpu_method __cpu_method_of_table_##name  \
                __used __section(__cpu_method_of_table)                 \
-               = { .method = _method, .ops = _ops }
+               = { .method = _method, .setup = _setup, .ops = _ops }
+
+#define CPU_METHOD_OF_DECLARE(name, _method, _ops)                     \
+       CPU_METHOD_OF_DECLARE_SETUP(name, _method, NULL, _ops)
+
 /*
  * set platform specific SMP operations
  */
diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c
index c7419a5..1a0cca3 100644
--- a/arch/arm/kernel/devtree.c
+++ b/arch/arm/kernel/devtree.c
@@ -76,11 +76,18 @@ static int __init set_smp_ops_by_method(struct device_node 
*node)
        if (of_property_read_string(node, "enable-method", &method))
                return 0;
 
-       for (; m < __cpu_method_of_table_end; m++)
+       for (; m < __cpu_method_of_table_end; m++) {
                if (!strcmp(m->method, method)) {
-                       smp_set_ops(m->ops);
-                       return 1;
+                       int ret = 0;
+
+                       if (m->setup)
+                               ret = m->setup(node);
+                       if (!ret)
+                               smp_set_ops(m->ops);
+
+                       return ret ? ret : 1;
                }
+       }
 
        return 0;
 }
@@ -181,16 +188,28 @@ void __init arm_dt_init_cpu_maps(void)
 
                tmp_map[i] = hwid;
 
-               if (!found_method)
+               if (!found_method) {
                        found_method = set_smp_ops_by_method(cpu);
+                       if (WARN(found_method < 0,
+                                       "error %d getting enable-method for "
+                                       "DT /cpu %u\n", found_method, cpuidx)) {
+                               return;
+                       }
+               }
        }
 
        /*
         * 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 (!found_method) {
+               found_method = set_smp_ops_by_method(cpus);
+               if (WARN(found_method < 0,
+                               "error %d getting enable-method for "
+                               "DT /cpus node\n", found_method)) {
+                       return;
+               }
+       }
 
        if (!bootcpu_valid) {
                pr_warn("DT missing boot CPU MPIDR[23:0], fall back to default 
cpu_logical_map\n");
-- 
1.7.9.5

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