static int __init pcc_cpufreq_probe()

in pcc-cpufreq.c [387:535]

• 125 lines of code
• 14 McCabe index (conditional complexity)

static int __init pcc_cpufreq_probe(void)
{
	acpi_status status;
	struct acpi_buffer output = {ACPI_ALLOCATE_BUFFER, NULL};
	struct pcc_memory_resource *mem_resource;
	struct pcc_register_resource *reg_resource;
	union acpi_object *out_obj, *member;
	acpi_handle handle, osc_handle;
	int ret = 0;

	status = acpi_get_handle(NULL, "\\_SB", &handle);
	if (ACPI_FAILURE(status))
		return -ENODEV;

	if (!acpi_has_method(handle, "PCCH"))
		return -ENODEV;

	status = acpi_get_handle(handle, "_OSC", &osc_handle);
	if (ACPI_SUCCESS(status)) {
		ret = pcc_cpufreq_do_osc(&osc_handle);
		if (ret)
			pr_debug("probe: _OSC evaluation did not succeed\n");
		/* Firmware's use of _OSC is optional */
		ret = 0;
	}

	status = acpi_evaluate_object(handle, "PCCH", NULL, &output);
	if (ACPI_FAILURE(status))
		return -ENODEV;

	out_obj = output.pointer;
	if (out_obj->type != ACPI_TYPE_PACKAGE) {
		ret = -ENODEV;
		goto out_free;
	}

	member = &out_obj->package.elements[0];
	if (member->type != ACPI_TYPE_BUFFER) {
		ret = -ENODEV;
		goto out_free;
	}

	mem_resource = (struct pcc_memory_resource *)member->buffer.pointer;

	pr_debug("probe: mem_resource descriptor: 0x%x,"
		" length: %d, space_id: %d, resource_usage: %d,"
		" type_specific: %d, granularity: 0x%llx,"
		" minimum: 0x%llx, maximum: 0x%llx,"
		" translation_offset: 0x%llx, address_length: 0x%llx\n",
		mem_resource->descriptor, mem_resource->length,
		mem_resource->space_id, mem_resource->resource_usage,
		mem_resource->type_specific, mem_resource->granularity,
		mem_resource->minimum, mem_resource->maximum,
		mem_resource->translation_offset,
		mem_resource->address_length);

	if (mem_resource->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) {
		ret = -ENODEV;
		goto out_free;
	}

	pcch_virt_addr = ioremap(mem_resource->minimum,
					mem_resource->address_length);
	if (pcch_virt_addr == NULL) {
		pr_debug("probe: could not map shared mem region\n");
		ret = -ENOMEM;
		goto out_free;
	}
	pcch_hdr = pcch_virt_addr;

	pr_debug("probe: PCCH header (virtual) addr: 0x%p\n", pcch_hdr);
	pr_debug("probe: PCCH header is at physical address: 0x%llx,"
		" signature: 0x%x, length: %d bytes, major: %d, minor: %d,"
		" supported features: 0x%x, command field: 0x%x,"
		" status field: 0x%x, nominal latency: %d us\n",
		mem_resource->minimum, ioread32(&pcch_hdr->signature),
		ioread16(&pcch_hdr->length), ioread8(&pcch_hdr->major),
		ioread8(&pcch_hdr->minor), ioread32(&pcch_hdr->features),
		ioread16(&pcch_hdr->command), ioread16(&pcch_hdr->status),
		ioread32(&pcch_hdr->latency));

	pr_debug("probe: min time between commands: %d us,"
		" max time between commands: %d us,"
		" nominal CPU frequency: %d MHz,"
		" minimum CPU frequency: %d MHz,"
		" minimum CPU frequency without throttling: %d MHz\n",
		ioread32(&pcch_hdr->minimum_time),
		ioread32(&pcch_hdr->maximum_time),
		ioread32(&pcch_hdr->nominal),
		ioread32(&pcch_hdr->throttled_frequency),
		ioread32(&pcch_hdr->minimum_frequency));

	member = &out_obj->package.elements[1];
	if (member->type != ACPI_TYPE_BUFFER) {
		ret = -ENODEV;
		goto pcch_free;
	}

	reg_resource = (struct pcc_register_resource *)member->buffer.pointer;

	doorbell.space_id = reg_resource->space_id;
	doorbell.bit_width = reg_resource->bit_width;
	doorbell.bit_offset = reg_resource->bit_offset;
	doorbell.access_width = 4;
	doorbell.address = reg_resource->address;

	pr_debug("probe: doorbell: space_id is %d, bit_width is %d, "
		"bit_offset is %d, access_width is %d, address is 0x%llx\n",
		doorbell.space_id, doorbell.bit_width, doorbell.bit_offset,
		doorbell.access_width, reg_resource->address);

	member = &out_obj->package.elements[2];
	if (member->type != ACPI_TYPE_INTEGER) {
		ret = -ENODEV;
		goto pcch_free;
	}

	doorbell_preserve = member->integer.value;

	member = &out_obj->package.elements[3];
	if (member->type != ACPI_TYPE_INTEGER) {
		ret = -ENODEV;
		goto pcch_free;
	}

	doorbell_write = member->integer.value;

	pr_debug("probe: doorbell_preserve: 0x%llx,"
		" doorbell_write: 0x%llx\n",
		doorbell_preserve, doorbell_write);

	pcc_cpu_info = alloc_percpu(struct pcc_cpu);
	if (!pcc_cpu_info) {
		ret = -ENOMEM;
		goto pcch_free;
	}

	printk(KERN_DEBUG "pcc-cpufreq: (v%s) driver loaded with frequency"
	       " limits: %d MHz, %d MHz\n", PCC_VERSION,
	       ioread32(&pcch_hdr->minimum_frequency),
	       ioread32(&pcch_hdr->nominal));
	kfree(output.pointer);
	return ret;
pcch_free:
	pcc_clear_mapping();
out_free:
	kfree(output.pointer);
	return ret;
}