ACPI: CPPC: implement support for SystemIO registers

According to the ACPI v6.2 (and later) specification, SystemIO can be
used for _CPC registers. This teaches cppc_acpi how to handle such
registers.

This patch was tested using the amd_pstate driver on my Zephyrus G15
(model GA503QS) using the current version 410 BIOS, which uses
a SystemIO register for the HighestPerformance element in _CPC.

Signed-off-by: Steven Noonan <steven@valvesoftware.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>

drivers/acpi/cppc_acpi.c

@@ -759,9 +759,24 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 						goto out_free;
 					cpc_ptr->cpc_regs[i-2].sys_mem_vaddr = addr;
 				}
+			} else if (gas_t->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
+				if (gas_t->access_width < 1 || gas_t->access_width > 3) {
+					/* 1 = 8-bit, 2 = 16-bit, and 3 = 32-bit. SystemIO doesn't
+					 * implement 64-bit registers.
+					 */
+					pr_debug("Invalid access width %d for SystemIO register\n",
+						gas_t->access_width);
+					goto out_free;
+				}
+				if (gas_t->address & ~0xFFFFULL) {
+					/* SystemIO registers use 16-bit integer addresses */
+					pr_debug("Invalid IO port %llu for SystemIO register\n",
+						gas_t->address);
+					goto out_free;
+				}
 			} else {
 				if (gas_t->space_id != ACPI_ADR_SPACE_FIXED_HARDWARE || !cpc_ffh_supported()) {
-					/* Support only PCC ,SYS MEM and FFH type regs */
+					/* Support only PCC, SystemMemory, SystemIO, and FFH type regs. */
 					pr_debug("Unsupported register type: %d\n", gas_t->space_id);
 					goto out_free;
 				}
@@ -936,7 +951,20 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 	}
 
 	*val = 0;
-	if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM && pcc_ss_id >= 0)
+
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
+		u32 width = 8 << (reg->access_width - 1);
+		acpi_status status;
+
+		status = acpi_os_read_port((acpi_io_address)reg->address, (u32 *)val, width);
+
+		if (status != AE_OK) {
+			pr_debug("Error: Failed to read SystemIO port %llx\n", reg->address);
+			return -EFAULT;
+		}
+
+		return 0;
+	} else if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM && pcc_ss_id >= 0)
 		vaddr = GET_PCC_VADDR(reg->address, pcc_ss_id);
 	else if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
 		vaddr = reg_res->sys_mem_vaddr;
@@ -975,7 +1003,19 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
 	struct cpc_reg *reg = &reg_res->cpc_entry.reg;
 
-	if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM && pcc_ss_id >= 0)
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
+		u32 width = 8 << (reg->access_width - 1);
+		acpi_status status;
+
+		status = acpi_os_write_port((acpi_io_address)reg->address, (u32)val, width);
+
+		if (status != AE_OK) {
+			pr_debug("Error: Failed to write SystemIO port %llx\n", reg->address);
+			return -EFAULT;
+		}
+
+		return 0;
+	} else if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM && pcc_ss_id >= 0)
 		vaddr = GET_PCC_VADDR(reg->address, pcc_ss_id);
 	else if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
 		vaddr = reg_res->sys_mem_vaddr;