arm64: kernel: implement ACPI parking protocol

The SBBR and ACPI specifications allow ACPI based systems that do not
implement PSCI (eg systems with no EL3) to boot through the ACPI parking
protocol specification[1].

This patch implements the ACPI parking protocol CPU operations, and adds
code that eases parsing the parking protocol data structures to the
ARM64 SMP initializion carried out at the same time as cpus enumeration.

To wake-up the CPUs from the parked state, this patch implements a
wakeup IPI for ARM64 (ie arch_send_wakeup_ipi_mask()) that mirrors the
ARM one, so that a specific IPI is sent for wake-up purpose in order
to distinguish it from other IPI sources.

Given the current ACPI MADT parsing API, the patch implements a glue
layer that helps passing MADT GICC data structure from SMP initialization
code to the parking protocol implementation somewhat overriding the CPU
operations interfaces. This to avoid creating a completely trasparent
DT/ACPI CPU operations layer that would require creating opaque
structure handling for CPUs data (DT represents CPU through DT nodes, ACPI
through static MADT table entries), which seems overkill given that ACPI
on ARM64 mandates only two booting protocols (PSCI and parking protocol),
so there is no need for further protocol additions.

Based on the original work by Mark Salter <[email protected]>

[1] https://acpica.org/sites/acpica/files/MP%20Startup%20for%20ARM%20platforms.docx

Signed-off-by: Lorenzo Pieralisi <[email protected]>
Tested-by: Loc Ho <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Hanjun Guo <[email protected]>
Cc: Sudeep Holla <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mark Salter <[email protected]>
Cc: Al Stone <[email protected]>
[[email protected]: Added WARN_ONCE(!acpi_parking_protocol_valid() on the IPI]
Signed-off-by: Catalin Marinas <[email protected]>

1 files changed, 23 insertions, 4 deletions

diff --git a/arch/arm64/kernel/cpu_ops.c b/arch/arm64/kernel/cpu_ops.c
index b6bd7d447768..c7cfb8fe06f9 100644
--- a/arch/arm64/kernel/cpu_ops.c
+++ b/arch/arm64/kernel/cpu_ops.c
@@ -25,19 +25,30 @@
 #include <asm/smp_plat.h>
 
 extern const struct cpu_operations smp_spin_table_ops;
+extern const struct cpu_operations acpi_parking_protocol_ops;
 extern const struct cpu_operations cpu_psci_ops;
 
 const struct cpu_operations *cpu_ops[NR_CPUS];
 
-static const struct cpu_operations *supported_cpu_ops[] __initconst = {
+static const struct cpu_operations *dt_supported_cpu_ops[] __initconst = {
 	&smp_spin_table_ops,
 	&cpu_psci_ops,
 	NULL,
 };
 
+static const struct cpu_operations *acpi_supported_cpu_ops[] __initconst = {
+#ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
+	&acpi_parking_protocol_ops,
+#endif
+	&cpu_psci_ops,
+	NULL,
+};
+
 static const struct cpu_operations * __init cpu_get_ops(const char *name)
 {
-	const struct cpu_operations **ops = supported_cpu_ops;
+	const struct cpu_operations **ops;
+
+	ops = acpi_disabled ? dt_supported_cpu_ops : acpi_supported_cpu_ops;
 
 	while (*ops) {
 		if (!strcmp(name, (*ops)->name))
@@ -75,8 +86,16 @@ static const char *__init cpu_read_enable_method(int cpu)
 		}
 	} else {
 		enable_method = acpi_get_enable_method(cpu);
-		if (!enable_method)
-			pr_err("Unsupported ACPI enable-method\n");
+		if (!enable_method) {
+			/*
+			 * In ACPI systems the boot CPU does not require
+			 * checking the enable method since for some
+			 * boot protocol (ie parking protocol) it need not
+			 * be initialized. Don't warn spuriously.
+			 */
+			if (cpu != 0)
+				pr_err("Unsupported ACPI enable-method\n");
+		}
 	}
 
 	return enable_method;