[PATCH V4 08/23] RISC-V: ACPI: Cache and retrieve the RINTC structure

[Sunil V L]

RINTC structures in the MADT provide mapping between the hartid
and the CPU. This is required many times even at run time like
cpuinfo. So, instead of parsing the ACPI table every time, cache
the RINTC structures and provide a function to get the correct
RINTC structure for a given cpu.

Signed-off-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
 arch/riscv/include/asm/acpi.h |  2 ++
 arch/riscv/kernel/acpi.c      | 60 +++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h
index 9be52b6ffae1..1606dce8992e 100644
--- a/arch/riscv/include/asm/acpi.h
+++ b/arch/riscv/include/asm/acpi.h
@@ -59,6 +59,8 @@ static inline bool acpi_has_cpu_in_madt(void)
 
 static inline void arch_fix_phys_package_id(int num, u32 slot) { }
 
+struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu);
+u32 get_acpi_id_for_cpu(int cpu);
 #endif /* CONFIG_ACPI */
 
 #endif /*_ASM_ACPI_H*/
diff --git a/arch/riscv/kernel/acpi.c b/arch/riscv/kernel/acpi.c
index 81d448c41714..40ab55309c70 100644
--- a/arch/riscv/kernel/acpi.c
+++ b/arch/riscv/kernel/acpi.c
@@ -24,6 +24,66 @@ EXPORT_SYMBOL(acpi_disabled);
 int acpi_pci_disabled = 1;	/* skip ACPI PCI scan and IRQ initialization */
 EXPORT_SYMBOL(acpi_pci_disabled);
 
+static struct acpi_madt_rintc cpu_madt_rintc[NR_CPUS];
+
+static int acpi_parse_madt_rintc(union acpi_subtable_headers *header, const unsigned long end)
+{
+	struct acpi_madt_rintc *rintc = (struct acpi_madt_rintc *)header;
+	int cpuid;
+
+	if (!(rintc->flags & ACPI_MADT_ENABLED))
+		return 0;
+
+	cpuid = riscv_hartid_to_cpuid(rintc->hart_id);
+	/*
+	 * When CONFIG_SMP is disabled, mapping won't be created for
+	 * all cpus.
+	 * CPUs more than NR_CPUS, will be ignored.
+	 */
+	if (cpuid >= 0 && cpuid < NR_CPUS)
+		cpu_madt_rintc[cpuid] = *rintc;
+
+	return 0;
+}
+
+static int acpi_init_rintc_array(void)
+{
+	if (acpi_table_parse_madt(ACPI_MADT_TYPE_RINTC, acpi_parse_madt_rintc, 0) > 0)
+		return 0;
+
+	return -ENODEV;
+}
+
+/*
+ * Instead of parsing (and freeing) the ACPI table, cache
+ * the RINTC structures since they are frequently used
+ * like in  cpuinfo.
+ */
+struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu)
+{
+	static bool rintc_init_done;
+
+	if (!rintc_init_done) {
+		if (acpi_init_rintc_array()) {
+			pr_err("No valid RINTC entries exist\n");
+			return NULL;
+		}
+
+		rintc_init_done = true;
+	}
+
+	return &cpu_madt_rintc[cpu];
+}
+
+u32 get_acpi_id_for_cpu(int cpu)
+{
+	struct acpi_madt_rintc *rintc = acpi_cpu_get_madt_rintc(cpu);
+
+	BUG_ON(!rintc);
+
+	return rintc->uid;
+}
+
 /*
  * __acpi_map_table() will be called before paging_init(), so early_ioremap()
  * or early_memremap() should be called here to for ACPI table mapping.
-- 
2.34.1