RISC-V: smpboot: Add ACPI support in setup_smp()

Enable SMP boot on ACPI based platforms by using the RINTC
structures in the MADT table.

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20230515054928.2079268-13-sunilvl@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/acpi.h

@@ -64,6 +64,8 @@ struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu);
 u32 get_acpi_id_for_cpu(int cpu);
 int acpi_get_riscv_isa(struct acpi_table_header *table,
 		       unsigned int cpu, const char **isa);
+
+static inline int acpi_numa_get_nid(unsigned int cpu) { return NUMA_NO_NODE; }
 #else
 static inline void acpi_init_rintc_map(void) { }
 static inline struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu)

arch/riscv/kernel/smpboot.c

@@ -8,6 +8,7 @@
  * Copyright (C) 2017 SiFive
  */
 
+#include <linux/acpi.h>
 #include <linux/arch_topology.h>
 #include <linux/module.h>
 #include <linux/init.h>
@@ -70,6 +71,72 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
 	}
 }
 
+#ifdef CONFIG_ACPI
+static unsigned int cpu_count = 1;
+
+static int __init acpi_parse_rintc(union acpi_subtable_headers *header, const unsigned long end)
+{
+	unsigned long hart;
+	static bool found_boot_cpu;
+	struct acpi_madt_rintc *processor = (struct acpi_madt_rintc *)header;
+
+	/*
+	 * Each RINTC structure in MADT will have a flag. If ACPI_MADT_ENABLED
+	 * bit in the flag is not enabled, it means OS should not try to enable
+	 * the cpu to which RINTC belongs.
+	 */
+	if (!(processor->flags & ACPI_MADT_ENABLED))
+		return 0;
+
+	if (BAD_MADT_ENTRY(processor, end))
+		return -EINVAL;
+
+	acpi_table_print_madt_entry(&header->common);
+
+	hart = processor->hart_id;
+	if (hart == INVALID_HARTID) {
+		pr_warn("Invalid hartid\n");
+		return 0;
+	}
+
+	if (hart == cpuid_to_hartid_map(0)) {
+		BUG_ON(found_boot_cpu);
+		found_boot_cpu = true;
+		early_map_cpu_to_node(0, acpi_numa_get_nid(cpu_count));
+		return 0;
+	}
+
+	if (cpu_count >= NR_CPUS) {
+		pr_warn("NR_CPUS is too small for the number of ACPI tables.\n");
+		return 0;
+	}
+
+	cpuid_to_hartid_map(cpu_count) = hart;
+	early_map_cpu_to_node(cpu_count, acpi_numa_get_nid(cpu_count));
+	cpu_count++;
+
+	return 0;
+}
+
+static void __init acpi_parse_and_init_cpus(void)
+{
+	int cpuid;
+
+	cpu_set_ops(0);
+
+	acpi_table_parse_madt(ACPI_MADT_TYPE_RINTC, acpi_parse_rintc, 0);
+
+	for (cpuid = 1; cpuid < nr_cpu_ids; cpuid++) {
+		if (cpuid_to_hartid_map(cpuid) != INVALID_HARTID) {
+			cpu_set_ops(cpuid);
+			set_cpu_possible(cpuid, true);
+		}
+	}
+}
+#else
+#define acpi_parse_and_init_cpus(...)	do { } while (0)
+#endif
+
 static void __init of_parse_and_init_cpus(void)
 {
 	struct device_node *dn;
@@ -118,7 +185,10 @@ static void __init of_parse_and_init_cpus(void)
 
 void __init setup_smp(void)
 {
-	of_parse_and_init_cpus();
+	if (acpi_disabled)
+		of_parse_and_init_cpus();
+	else
+		acpi_parse_and_init_cpus();
 }
 
 static int start_secondary_cpu(int cpu, struct task_struct *tidle)