int acpi_processor_evaluate_cst()

in acpi_processor.c [729:891]

• 116 lines of code
• 23 McCabe index (conditional complexity)

int acpi_processor_evaluate_cst(acpi_handle handle, u32 cpu,
				struct acpi_processor_power *info)
{
	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
	union acpi_object *cst;
	acpi_status status;
	u64 count;
	int last_index = 0;
	int i, ret = 0;

	status = acpi_evaluate_object(handle, "_CST", NULL, &buffer);
	if (ACPI_FAILURE(status)) {
		acpi_handle_debug(handle, "No _CST\n");
		return -ENODEV;
	}

	cst = buffer.pointer;

	/* There must be at least 2 elements. */
	if (!cst || cst->type != ACPI_TYPE_PACKAGE || cst->package.count < 2) {
		acpi_handle_warn(handle, "Invalid _CST output\n");
		ret = -EFAULT;
		goto end;
	}

	count = cst->package.elements[0].integer.value;

	/* Validate the number of C-states. */
	if (count < 1 || count != cst->package.count - 1) {
		acpi_handle_warn(handle, "Inconsistent _CST data\n");
		ret = -EFAULT;
		goto end;
	}

	for (i = 1; i <= count; i++) {
		union acpi_object *element;
		union acpi_object *obj;
		struct acpi_power_register *reg;
		struct acpi_processor_cx cx;

		/*
		 * If there is not enough space for all C-states, skip the
		 * excess ones and log a warning.
		 */
		if (last_index >= ACPI_PROCESSOR_MAX_POWER - 1) {
			acpi_handle_warn(handle,
					 "No room for more idle states (limit: %d)\n",
					 ACPI_PROCESSOR_MAX_POWER - 1);
			break;
		}

		memset(&cx, 0, sizeof(cx));

		element = &cst->package.elements[i];
		if (element->type != ACPI_TYPE_PACKAGE) {
			acpi_handle_info(handle, "_CST C%d type(%x) is not package, skip...\n",
					 i, element->type);
			continue;
		}

		if (element->package.count != 4) {
			acpi_handle_info(handle, "_CST C%d package count(%d) is not 4, skip...\n",
					 i, element->package.count);
			continue;
		}

		obj = &element->package.elements[0];

		if (obj->type != ACPI_TYPE_BUFFER) {
			acpi_handle_info(handle, "_CST C%d package element[0] type(%x) is not buffer, skip...\n",
					 i, obj->type);
			continue;
		}

		reg = (struct acpi_power_register *)obj->buffer.pointer;

		obj = &element->package.elements[1];
		if (obj->type != ACPI_TYPE_INTEGER) {
			acpi_handle_info(handle, "_CST C[%d] package element[1] type(%x) is not integer, skip...\n",
					 i, obj->type);
			continue;
		}

		cx.type = obj->integer.value;
		/*
		 * There are known cases in which the _CST output does not
		 * contain C1, so if the type of the first state found is not
		 * C1, leave an empty slot for C1 to be filled in later.
		 */
		if (i == 1 && cx.type != ACPI_STATE_C1)
			last_index = 1;

		cx.address = reg->address;
		cx.index = last_index + 1;

		if (reg->space_id == ACPI_ADR_SPACE_FIXED_HARDWARE) {
			if (!acpi_processor_ffh_cstate_probe(cpu, &cx, reg)) {
				/*
				 * In the majority of cases _CST describes C1 as
				 * a FIXED_HARDWARE C-state, but if the command
				 * line forbids using MWAIT, use CSTATE_HALT for
				 * C1 regardless.
				 */
				if (cx.type == ACPI_STATE_C1 &&
				    boot_option_idle_override == IDLE_NOMWAIT) {
					cx.entry_method = ACPI_CSTATE_HALT;
					snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT");
				} else {
					cx.entry_method = ACPI_CSTATE_FFH;
				}
			} else if (cx.type == ACPI_STATE_C1) {
				/*
				 * In the special case of C1, FIXED_HARDWARE can
				 * be handled by executing the HLT instruction.
				 */
				cx.entry_method = ACPI_CSTATE_HALT;
				snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT");
			} else {
				acpi_handle_info(handle, "_CST C%d declares FIXED_HARDWARE C-state but not supported in hardware, skip...\n",
						 i);
				continue;
			}
		} else if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
			cx.entry_method = ACPI_CSTATE_SYSTEMIO;
			snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI IOPORT 0x%x",
				 cx.address);
		} else {
			acpi_handle_info(handle, "_CST C%d space_id(%x) neither FIXED_HARDWARE nor SYSTEM_IO, skip...\n",
					 i, reg->space_id);
			continue;
		}

		if (cx.type == ACPI_STATE_C1)
			cx.valid = 1;

		obj = &element->package.elements[2];
		if (obj->type != ACPI_TYPE_INTEGER) {
			acpi_handle_info(handle, "_CST C%d package element[2] type(%x) not integer, skip...\n",
					 i, obj->type);
			continue;
		}

		cx.latency = obj->integer.value;

		obj = &element->package.elements[3];
		if (obj->type != ACPI_TYPE_INTEGER) {
			acpi_handle_info(handle, "_CST C%d package element[3] type(%x) not integer, skip...\n",
					 i, obj->type);
			continue;
		}

		memcpy(&info->states[++last_index], &cx, sizeof(cx));
	}

	acpi_handle_info(handle, "Found %d idle states\n", last_index);

	info->count = last_index;

end:
	kfree(buffer.pointer);

	return ret;
}