ARM64: kernel: make cpu_ops hooks DT agnostic

ARM64 CPU operations such as cpu_init and cpu_init_idle take
a struct device_node pointer as a parameter, which corresponds to
the device tree node of the logical cpu on which the operation
has to be applied.

With the advent of ACPI on arm64, where MADT static table entries
are used to initialize cpus, the device tree node parameter
in cpu_ops hooks become useless when booting with ACPI, since
in that case cpu device tree nodes are not present and can not be
used for cpu initialization.

The current cpu_init hook requires a struct device_node pointer
parameter because it is called while parsing the device tree to
initialize CPUs, when the cpu_logical_map (that is used to match
a cpu node reg property to a device tree node) for a given logical
cpu id is not set up yet. This means that the cpu_init hook cannot
rely on the of_get_cpu_node function to retrieve the device tree
node corresponding to the logical cpu id passed in as parameter,
so the cpu device tree node must be passed in as a parameter to fix
this catch-22 dependency cycle.

This patch reshuffles the cpu_logical_map initialization code so
that the cpu_init cpu_ops hook can safely use the of_get_cpu_node
function to retrieve the cpu device tree node, removing the need for
the device tree node pointer parameter.

In the process, the patch removes device tree node parameters
from all cpu_ops hooks, in preparation for SMP DT/ACPI cpus
initialization consolidation.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Hanjun Guo <hanjun.guo@linaro.org>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Hanjun Guo <hanjun.guo@linaro.org>
Tested-by: Mark Rutland <mark.rutland@arm.com> [DT]
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 15 insertions, 11 deletions

diff --git a/arch/arm64/include/asm/cpu_ops.h b/arch/arm64/include/asm/cpu_ops.h
index 5a31d6716914..7d8b999d1a2b 100644
--- a/arch/arm64/include/asm/cpu_ops.h
+++ b/arch/arm64/include/asm/cpu_ops.h
@@ -19,15 +19,15 @@
 #include <linux/init.h>
 #include <linux/threads.h>
 
-struct device_node;
-
 /**
  * struct cpu_operations - Callback operations for hotplugging CPUs.
  *
  * @name:	Name of the property as appears in a devicetree cpu node's
- *		enable-method property.
- * @cpu_init:	Reads any data necessary for a specific enable-method from the
- *		devicetree, for a given cpu node and proposed logical id.
+ *		enable-method property. On systems booting with ACPI, @name
+ *		identifies the struct cpu_operations entry corresponding to
+ *		the boot protocol specified in the ACPI MADT table.
+ * @cpu_init:	Reads any data necessary for a specific enable-method for a
+ *		proposed logical id.
  * @cpu_prepare: Early one-time preparation step for a cpu. If there is a
  *		mechanism for doing so, tests whether it is possible to boot
  *		the given CPU.
@@ -40,15 +40,15 @@ struct device_node;
  * @cpu_die:	Makes a cpu leave the kernel. Must not fail. Called from the
  *		cpu being killed.
  * @cpu_kill:  Ensures a cpu has left the kernel. Called from another cpu.
- * @cpu_init_idle: Reads any data necessary to initialize CPU idle states from
- *		devicetree, for a given cpu node and proposed logical id.
+ * @cpu_init_idle: Reads any data necessary to initialize CPU idle states for
+ *		   a proposed logical id.
  * @cpu_suspend: Suspends a cpu and saves the required context. May fail owing
  *               to wrong parameters or error conditions. Called from the
  *               CPU being suspended. Must be called with IRQs disabled.
  */
 struct cpu_operations {
 	const char	*name;
-	int		(*cpu_init)(struct device_node *, unsigned int);
+	int		(*cpu_init)(unsigned int);
 	int		(*cpu_prepare)(unsigned int);
 	int		(*cpu_boot)(unsigned int);
 	void		(*cpu_postboot)(void);
@@ -58,14 +58,18 @@ struct cpu_operations {
 	int		(*cpu_kill)(unsigned int cpu);
 #endif
 #ifdef CONFIG_CPU_IDLE
-	int		(*cpu_init_idle)(struct device_node *, unsigned int);
+	int		(*cpu_init_idle)(unsigned int);
 	int		(*cpu_suspend)(unsigned long);
 #endif
 };
 
 extern const struct cpu_operations *cpu_ops[NR_CPUS];
-int __init cpu_read_ops(struct device_node *dn, int cpu);
-void __init cpu_read_bootcpu_ops(void);
+int __init cpu_read_ops(int cpu);
 const struct cpu_operations *cpu_get_ops(const char *name);
 
+static inline void __init cpu_read_bootcpu_ops(void)
+{
+	cpu_read_ops(0);
+}
+
 #endif /* ifndef __ASM_CPU_OPS_H */