drivers/acpi/acpi_lpit.c

Source file repositories/reference/linux-study-clean/drivers/acpi/acpi_lpit.c

File Facts

System
Linux kernel
Corpus path
drivers/acpi/acpi_lpit.c
Extension
.c
Size
4279 bytes
Lines
163
Domain
Driver Families
Bucket
drivers/acpi
Inferred role
Driver Families: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct lpit_residency_info {
	struct acpi_generic_address gaddr;
	u64 frequency;
	void __iomem *iomem_addr;
};

/* Storage for an memory mapped and FFH based entries */
static struct lpit_residency_info residency_info_mem;
static struct lpit_residency_info residency_info_ffh;

static int lpit_read_residency_counter_us(u64 *counter, bool io_mem)
{
	int err;

	if (io_mem) {
		u64 count = 0;
		int error;

		error = acpi_os_read_iomem(residency_info_mem.iomem_addr, &count,
					   residency_info_mem.gaddr.bit_width);
		if (error)
			return error;

		*counter = div64_u64(count * 1000000ULL, residency_info_mem.frequency);
		return 0;
	}

	err = rdmsrq_safe(residency_info_ffh.gaddr.address, counter);
	if (!err) {
		u64 mask = GENMASK_ULL(residency_info_ffh.gaddr.bit_offset +
				       residency_info_ffh.gaddr. bit_width - 1,
				       residency_info_ffh.gaddr.bit_offset);

		*counter &= mask;
		*counter >>= residency_info_ffh.gaddr.bit_offset;
		*counter = div64_u64(*counter * 1000000ULL, residency_info_ffh.frequency);
		return 0;
	}

	return -ENODATA;
}

static ssize_t low_power_idle_system_residency_us_show(struct device *dev,
						       struct device_attribute *attr,
						       char *buf)
{
	u64 counter;
	int ret;

	ret = lpit_read_residency_counter_us(&counter, true);
	if (ret)
		return ret;

	return sprintf(buf, "%llu\n", counter);
}
static DEVICE_ATTR_RO(low_power_idle_system_residency_us);

static ssize_t low_power_idle_cpu_residency_us_show(struct device *dev,
						    struct device_attribute *attr,
						    char *buf)
{
	u64 counter;
	int ret;

	ret = lpit_read_residency_counter_us(&counter, false);
	if (ret)
		return ret;

	return sprintf(buf, "%llu\n", counter);
}
static DEVICE_ATTR_RO(low_power_idle_cpu_residency_us);

int lpit_read_residency_count_address(u64 *address)
{
	if (!residency_info_mem.gaddr.address)
		return -EINVAL;

	*address = residency_info_mem.gaddr.address;

	return 0;
}
EXPORT_SYMBOL_GPL(lpit_read_residency_count_address);

static void lpit_update_residency(struct lpit_residency_info *info,
				 struct acpi_lpit_native *lpit_native)
{
	struct device *dev_root = bus_get_dev_root(&cpu_subsys);

	/* Silently fail, if cpuidle attribute group is not present */
	if (!dev_root)

Annotation

Implementation Notes