RISC-V: ACPI: Cache and retrieve the RINTC structure

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@ventanamicro.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20230515054928.2079268-10-sunilvl@ventanamicro.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/acpi.h

@@ -59,6 +59,16 @@ static inline bool acpi_has_cpu_in_madt(void)
 
 static inline void arch_fix_phys_package_id(int num, u32 slot) { }
 
+void acpi_init_rintc_map(void);
+struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu);
+u32 get_acpi_id_for_cpu(int cpu);
+#else
+static inline void acpi_init_rintc_map(void) { }
+static inline struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu)
+{
+	return NULL;
+}
+
 #endif /* CONFIG_ACPI */
 
 #endif /*_ASM_ACPI_H*/

arch/riscv/kernel/acpi.c

@@ -29,6 +29,8 @@ static bool param_acpi_off __initdata;
 static bool param_acpi_on __initdata;
 static bool param_acpi_force __initdata;
 
+static struct acpi_madt_rintc cpu_madt_rintc[NR_CPUS];
+
 static int __init parse_acpi(char *arg)
 {
 	if (!arg)
@@ -150,6 +152,49 @@ void __init acpi_boot_table_init(void)
 	}
 }
 
+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 num_possible_cpus, will be ignored.
+	 */
+	if (cpuid >= 0 && cpuid < num_possible_cpus())
+		cpu_madt_rintc[cpuid] = *rintc;
+
+	return 0;
+}
+
+/*
+ * Instead of parsing (and freeing) the ACPI table, cache
+ * the RINTC structures since they are frequently used
+ * like in  cpuinfo.
+ */
+void __init acpi_init_rintc_map(void)
+{
+	if (acpi_table_parse_madt(ACPI_MADT_TYPE_RINTC, acpi_parse_madt_rintc, 0) <= 0) {
+		pr_err("No valid RINTC entries exist\n");
+		BUG();
+	}
+}
+
+struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu)
+{
+	return &cpu_madt_rintc[cpu];
+}
+
+u32 get_acpi_id_for_cpu(int cpu)
+{
+	return acpi_cpu_get_madt_rintc(cpu)->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.

arch/riscv/kernel/setup.c

@@ -22,6 +22,7 @@
 #include <linux/efi.h>
 #include <linux/crash_dump.h>
 
+#include <asm/acpi.h>
 #include <asm/alternative.h>
 #include <asm/cacheflush.h>
 #include <asm/cpu_ops.h>
@@ -298,6 +299,9 @@ void __init setup_arch(char **cmdline_p)
 	setup_smp();
 #endif
 
+	if (!acpi_disabled)
+		acpi_init_rintc_map();
+
 	riscv_init_cbo_blocksizes();
 	riscv_fill_hwcap();
 	apply_boot_alternatives();