[PATCH 16/19] arm64: cpu_ops: Expose optional argument to target cpu in ->cpu_boot()

[Will Deacon]

Some backend implementations of 'struct cpu_ops', notably PSCI v0.2+,
allow an optional argument to be passed in register X0 to the target
CPU during boot.

Expose this functionality by extending the ->cpu_boot() CPU operation
to take an additional argument which is ignored unless the new optional
->cpu_boot_has_arg() callback is present and returns 'true'. For now,
we continue to pass zero.

Signed-off-by: Will Deacon <will at kernel.org>
---
 arch/arm64/include/asm/cpu_ops.h          |  6 +++++-
 arch/arm64/kernel/acpi_parking_protocol.c |  3 ++-
 arch/arm64/kernel/psci.c                  | 11 +++++++++--
 arch/arm64/kernel/smp.c                   |  2 +-
 arch/arm64/kernel/smp_spin_table.c        |  2 +-
 5 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/cpu_ops.h b/arch/arm64/include/asm/cpu_ops.h
index cd298a8710d8..e7662a1879d9 100644
--- a/arch/arm64/include/asm/cpu_ops.h
+++ b/arch/arm64/include/asm/cpu_ops.h
@@ -21,6 +21,9 @@
  *		mechanism for doing so, tests whether it is possible to boot
  *		the given CPU.
  * @cpu_boot:	Boots a cpu into the kernel.
+ * @cpu_boot_has_arg: Optionally determines whether @cpu_boot passes its
+ *		      (non-zero) second argument to the booting CPU in
+ *		      register x0.
  * @cpu_postboot: Optionally, perform any post-boot cleanup or necessary
  *		synchronisation. Called from the cpu being booted.
  * @cpu_can_disable: Determines whether a CPU can be disabled based on
@@ -36,7 +39,8 @@ struct cpu_operations {
 	const char	*name;
 	int		(*cpu_init)(unsigned int);
 	int		(*cpu_prepare)(unsigned int);
-	int		(*cpu_boot)(unsigned int);
+	int		(*cpu_boot)(unsigned int, unsigned long);
+	bool		(*cpu_boot_has_arg)(void);
 	void		(*cpu_postboot)(void);
 #ifdef CONFIG_HOTPLUG_CPU
 	bool		(*cpu_can_disable)(unsigned int cpu);
diff --git a/arch/arm64/kernel/acpi_parking_protocol.c b/arch/arm64/kernel/acpi_parking_protocol.c
index e1be29e608b7..24ebde1241bf 100644
--- a/arch/arm64/kernel/acpi_parking_protocol.c
+++ b/arch/arm64/kernel/acpi_parking_protocol.c
@@ -56,7 +56,8 @@ static int acpi_parking_protocol_cpu_prepare(unsigned int cpu)
 	return 0;
 }
 
-static int acpi_parking_protocol_cpu_boot(unsigned int cpu)
+static int acpi_parking_protocol_cpu_boot(unsigned int cpu,
+					  unsigned long ignored)
 {
 	struct cpu_mailbox_entry *cpu_entry = &cpu_mailbox_entries[cpu];
 	struct parking_protocol_mailbox __iomem *mailbox;
diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
index 6b25a12ed143..3ba4fa14b9e3 100644
--- a/arch/arm64/kernel/psci.c
+++ b/arch/arm64/kernel/psci.c
@@ -36,16 +36,22 @@ static int __init cpu_psci_cpu_prepare(unsigned int cpu)
 	return 0;
 }
 
-static int cpu_psci_cpu_boot(unsigned int cpu)
+static int cpu_psci_cpu_boot(unsigned int cpu, unsigned long context)
 {
 	phys_addr_t pa_secondary_entry = __pa_symbol(secondary_entry);
-	int err = psci_ops.cpu_on(cpu_logical_map(cpu), pa_secondary_entry, 0);
+	int err = psci_ops.cpu_on(cpu_logical_map(cpu), pa_secondary_entry,
+				  context);
 	if (err && err != -EPERM)
 		pr_err("failed to boot CPU%d (%d)\n", cpu, err);
 
 	return err;
 }
 
+static bool cpu_psci_cpu_boot_has_context(void)
+{
+	return psci_ops.get_version() >= PSCI_VERSION(0, 2);
+}
+
 #ifdef CONFIG_HOTPLUG_CPU
 static bool cpu_psci_cpu_can_disable(unsigned int cpu)
 {
@@ -114,6 +120,7 @@ const struct cpu_operations cpu_psci_ops = {
 	.cpu_init	= cpu_psci_cpu_init,
 	.cpu_prepare	= cpu_psci_cpu_prepare,
 	.cpu_boot	= cpu_psci_cpu_boot,
+	.cpu_boot_has_arg = cpu_psci_cpu_boot_has_context,
 #ifdef CONFIG_HOTPLUG_CPU
 	.cpu_can_disable = cpu_psci_cpu_can_disable,
 	.cpu_disable	= cpu_psci_cpu_disable,
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 2e98a92eb764..b57f8f752f78 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -103,7 +103,7 @@ static int boot_secondary(unsigned int cpu, struct task_struct *idle)
 	const struct cpu_operations *ops = get_secondary_cpu_ops();
 
 	if (ops->cpu_boot)
-		return ops->cpu_boot(cpu);
+		return ops->cpu_boot(cpu, 0);
 
 	return -EOPNOTSUPP;
 }
diff --git a/arch/arm64/kernel/smp_spin_table.c b/arch/arm64/kernel/smp_spin_table.c
index 49029eace3ad..a5e6f444c25f 100644
--- a/arch/arm64/kernel/smp_spin_table.c
+++ b/arch/arm64/kernel/smp_spin_table.c
@@ -104,7 +104,7 @@ static int smp_spin_table_cpu_prepare(unsigned int cpu)
 	return 0;
 }
 
-static int smp_spin_table_cpu_boot(unsigned int cpu)
+static int smp_spin_table_cpu_boot(unsigned int cpu, unsigned long ignored)
 {
 	/*
 	 * Update the pen release flag.
-- 
2.55.0.979.g7e5102b832-goog