drivers/acpi/acpi_lpss.c

/*
 * ACPI support for Intel Lynxpoint LPSS.
 *
 * Copyright (C) 2013, Intel Corporation
 * Authors: Mika Westerberg <mika.westerberg@linux.intel.com>
 *          Rafael J. Wysocki <rafael.j.wysocki@intel.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/acpi.h>
#include <linux/clkdev.h>
#include <linux/clk-provider.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/platform_data/clk-lpss.h>
#include <linux/platform_data/x86/pmc_atom.h>
#include <linux/pm_domain.h>
#include <linux/pm_runtime.h>
#include <linux/pwm.h>
#include <linux/delay.h>

#include "internal.h"

ACPI_MODULE_NAME("acpi_lpss");

#ifdef CONFIG_X86_INTEL_LPSS

#include <asm/cpu_device_id.h>
#include <asm/intel-family.h>
#include <asm/iosf_mbi.h>

#define LPSS_ADDR(desc) ((unsigned long)&desc)

#define LPSS_CLK_SIZE	0x04
#define LPSS_LTR_SIZE	0x18

/* Offsets relative to LPSS_PRIVATE_OFFSET */
#define LPSS_CLK_DIVIDER_DEF_MASK	(BIT(1) | BIT(16))
#define LPSS_RESETS			0x04
#define LPSS_RESETS_RESET_FUNC		BIT(0)
#define LPSS_RESETS_RESET_APB		BIT(1)
#define LPSS_GENERAL			0x08
#define LPSS_GENERAL_LTR_MODE_SW	BIT(2)
#define LPSS_GENERAL_UART_RTS_OVRD	BIT(3)
#define LPSS_SW_LTR			0x10
#define LPSS_AUTO_LTR			0x14
#define LPSS_LTR_SNOOP_REQ		BIT(15)
#define LPSS_LTR_SNOOP_MASK		0x0000FFFF
#define LPSS_LTR_SNOOP_LAT_1US		0x800
#define LPSS_LTR_SNOOP_LAT_32US		0xC00
#define LPSS_LTR_SNOOP_LAT_SHIFT	5
#define LPSS_LTR_SNOOP_LAT_CUTOFF	3000
#define LPSS_LTR_MAX_VAL		0x3FF
#define LPSS_TX_INT			0x20
#define LPSS_TX_INT_MASK		BIT(1)

#define LPSS_PRV_REG_COUNT		9

/* LPSS Flags */
#define LPSS_CLK			BIT(0)
#define LPSS_CLK_GATE			BIT(1)
#define LPSS_CLK_DIVIDER		BIT(2)
#define LPSS_LTR			BIT(3)
#define LPSS_SAVE_CTX			BIT(4)
#define LPSS_NO_D3_DELAY		BIT(5)

struct lpss_private_data;

struct lpss_device_desc {
	unsigned int flags;
	const char *clk_con_id;
	unsigned int prv_offset;
	size_t prv_size_override;
	struct property_entry *properties;
	void (*setup)(struct lpss_private_data *pdata);
};

static const struct lpss_device_desc lpss_dma_desc = {
	.flags = LPSS_CLK,
};

struct lpss_private_data {
	struct acpi_device *adev;
	void __iomem *mmio_base;
	resource_size_t mmio_size;
	unsigned int fixed_clk_rate;
	struct clk *clk;
	const struct lpss_device_desc *dev_desc;
	u32 prv_reg_ctx[LPSS_PRV_REG_COUNT];
};

/* LPSS run time quirks */
static unsigned int lpss_quirks;

/*
 * LPSS_QUIRK_ALWAYS_POWER_ON: override power state for LPSS DMA device.
 *
 * The LPSS DMA controller has neither _PS0 nor _PS3 method. Moreover
 * it can be powered off automatically whenever the last LPSS device goes down.
 * In case of no power any access to the DMA controller will hang the system.
 * The behaviour is reproduced on some HP laptops based on Intel BayTrail as
 * well as on ASuS T100TA transformer.
 *
 * This quirk overrides power state of entire LPSS island to keep DMA powered
 * on whenever we have at least one other device in use.
 */
#define LPSS_QUIRK_ALWAYS_POWER_ON	BIT(0)

/* UART Component Parameter Register */
#define LPSS_UART_CPR			0xF4
#define LPSS_UART_CPR_AFCE		BIT(4)

static void lpss_uart_setup(struct lpss_private_data *pdata)
{
	unsigned int offset;
	u32 val;

	offset = pdata->dev_desc->prv_offset + LPSS_TX_INT;
	val = readl(pdata->mmio_base + offset);
	writel(val | LPSS_TX_INT_MASK, pdata->mmio_base + offset);

	val = readl(pdata->mmio_base + LPSS_UART_CPR);
	if (!(val & LPSS_UART_CPR_AFCE)) {
		offset = pdata->dev_desc->prv_offset + LPSS_GENERAL;
		val = readl(pdata->mmio_base + offset);
		val |= LPSS_GENERAL_UART_RTS_OVRD;
		writel(val, pdata->mmio_base + offset);
	}
}

static void lpss_deassert_reset(struct lpss_private_data *pdata)
{
	unsigned int offset;
	u32 val;

	offset = pdata->dev_desc->prv_offset + LPSS_RESETS;
	val = readl(pdata->mmio_base + offset);
	val |= LPSS_RESETS_RESET_APB | LPSS_RESETS_RESET_FUNC;
	writel(val, pdata->mmio_base + offset);
}

/*
 * BYT PWM used for backlight control by the i915 driver on systems without
 * the Crystal Cove PMIC.
 */
static struct pwm_lookup byt_pwm_lookup[] = {
	PWM_LOOKUP_WITH_MODULE("80860F09:00", 0, "0000:00:02.0",
			       "pwm_backlight", 0, PWM_POLARITY_NORMAL,
			       "pwm-lpss-platform"),
};

static void byt_pwm_setup(struct lpss_private_data *pdata)
{
	struct acpi_device *adev = pdata->adev;

	/* Only call pwm_add_table for the first PWM controller */
	if (!adev->pnp.unique_id || strcmp(adev->pnp.unique_id, "1"))
		return;

	if (!acpi_dev_present("INT33FD", NULL, -1))
		pwm_add_table(byt_pwm_lookup, ARRAY_SIZE(byt_pwm_lookup));
}

#define LPSS_I2C_ENABLE			0x6c

static void byt_i2c_setup(struct lpss_private_data *pdata)
{
	lpss_deassert_reset(pdata);

	if (readl(pdata->mmio_base + pdata->dev_desc->prv_offset))
		pdata->fixed_clk_rate = 133000000;

	writel(0, pdata->mmio_base + LPSS_I2C_ENABLE);
}

/* BSW PWM used for backlight control by the i915 driver */
static struct pwm_lookup bsw_pwm_lookup[] = {
	PWM_LOOKUP_WITH_MODULE("80862288:00", 0, "0000:00:02.0",
			       "pwm_backlight", 0, PWM_POLARITY_NORMAL,
			       "pwm-lpss-platform"),
};

static void bsw_pwm_setup(struct lpss_private_data *pdata)
{
	struct acpi_device *adev = pdata->adev;

	/* Only call pwm_add_table for the first PWM controller */
	if (!adev->pnp.unique_id || strcmp(adev->pnp.unique_id, "1"))
		return;

	pwm_add_table(bsw_pwm_lookup, ARRAY_SIZE(bsw_pwm_lookup));
}

static const struct lpss_device_desc lpt_dev_desc = {
	.flags = LPSS_CLK | LPSS_CLK_GATE | LPSS_CLK_DIVIDER | LPSS_LTR,
	.prv_offset = 0x800,
};

static const struct lpss_device_desc lpt_i2c_dev_desc = {
	.flags = LPSS_CLK | LPSS_CLK_GATE | LPSS_LTR,
	.prv_offset = 0x800,
};

static struct property_entry uart_properties[] = {
	PROPERTY_ENTRY_U32("reg-io-width", 4),
	PROPERTY_ENTRY_U32("reg-shift", 2),
	PROPERTY_ENTRY_BOOL("snps,uart-16550-compatible"),
	{ },
};

static const struct lpss_device_desc lpt_uart_dev_desc = {
	.flags = LPSS_CLK | LPSS_CLK_GATE | LPSS_CLK_DIVIDER | LPSS_LTR,
	.clk_con_id = "baudclk",
	.prv_offset = 0x800,
	.setup = lpss_uart_setup,
	.properties = uart_properties,
};

static const struct lpss_device_desc lpt_sdio_dev_desc = {
	.flags = LPSS_LTR,
	.prv_offset = 0x1000,
	.prv_size_override = 0x1018,
};

static const struct lpss_device_desc byt_pwm_dev_desc = {
	.flags = LPSS_SAVE_CTX,
	.setup = byt_pwm_setup,
};

static const struct lpss_device_desc bsw_pwm_dev_desc = {
	.flags = LPSS_SAVE_CTX | LPSS_NO_D3_DELAY,
	.setup = bsw_pwm_setup,
};

static const struct lpss_device_desc byt_uart_dev_desc = {
	.flags = LPSS_CLK | LPSS_CLK_GATE | LPSS_CLK_DIVIDER | LPSS_SAVE_CTX,
	.clk_con_id = "baudclk",
	.prv_offset = 0x800,
	.setup = lpss_uart_setup,
	.properties = uart_properties,
};

static const struct lpss_device_desc bsw_uart_dev_desc = {
	.flags = LPSS_CLK | LPSS_CLK_GATE | LPSS_CLK_DIVIDER | LPSS_SAVE_CTX
			| LPSS_NO_D3_DELAY,
	.clk_con_id = "baudclk",
	.prv_offset = 0x800,
	.setup = lpss_uart_setup,
	.properties = uart_properties,
};

static const struct lpss_device_desc byt_spi_dev_desc = {
	.flags = LPSS_CLK | LPSS_CLK_GATE | LPSS_CLK_DIVIDER | LPSS_SAVE_CTX,
	.prv_offset = 0x400,
};

static const struct lpss_device_desc byt_sdio_dev_desc = {
	.flags = LPSS_CLK,
};

static const struct lpss_device_desc byt_i2c_dev_desc = {
	.flags = LPSS_CLK | LPSS_SAVE_CTX,
	.prv_offset = 0x800,
	.setup = byt_i2c_setup,
};

static const struct lpss_device_desc bsw_i2c_dev_desc = {
	.flags = LPSS_CLK | LPSS_SAVE_CTX | LPSS_NO_D3_DELAY,
	.prv_offset = 0x800,
	.setup = byt_i2c_setup,
};

static const struct lpss_device_desc bsw_spi_dev_desc = {
	.flags = LPSS_CLK | LPSS_CLK_GATE | LPSS_CLK_DIVIDER | LPSS_SAVE_CTX
			| LPSS_NO_D3_DELAY,
	.prv_offset = 0x400,
	.setup = lpss_deassert_reset,
};

#define ICPU(model)	{ X86_VENDOR_INTEL, 6, model, X86_FEATURE_ANY, }

static const struct x86_cpu_id lpss_cpu_ids[] = {
	ICPU(INTEL_FAM6_ATOM_SILVERMONT1),	/* Valleyview, Bay Trail */
	ICPU(INTEL_FAM6_ATOM_AIRMONT),	/* Braswell, Cherry Trail */
	{}
};

#else

#define LPSS_ADDR(desc) (0UL)

#endif /* CONFIG_X86_INTEL_LPSS */

static const struct acpi_device_id acpi_lpss_device_ids[] = {
	/* Generic LPSS devices */
	{ "INTL9C60", LPSS_ADDR(lpss_dma_desc) },

	/* Lynxpoint LPSS devices */
	{ "INT33C0", LPSS_ADDR(lpt_dev_desc) },
	{ "INT33C1", LPSS_ADDR(lpt_dev_desc) },
	{ "INT33C2", LPSS_ADDR(lpt_i2c_dev_desc) },
	{ "INT33C3", LPSS_ADDR(lpt_i2c_dev_desc) },
	{ "INT33C4", LPSS_ADDR(lpt_uart_dev_desc) },
	{ "INT33C5", LPSS_ADDR(lpt_uart_dev_desc) },
	{ "INT33C6", LPSS_ADDR(lpt_sdio_dev_desc) },
	{ "INT33C7", },

	/* BayTrail LPSS devices */
	{ "80860F09", LPSS_ADDR(byt_pwm_dev_desc) },
	{ "80860F0A", LPSS_ADDR(byt_uart_dev_desc) },
	{ "80860F0E", LPSS_ADDR(byt_spi_dev_desc) },
	{ "80860F14", LPSS_ADDR(byt_sdio_dev_desc) },
	{ "80860F41", LPSS_ADDR(byt_i2c_dev_desc) },
	{ "INT33B2", },
	{ "INT33FC", },

	/* Braswell LPSS devices */
	{ "80862288", LPSS_ADDR(bsw_pwm_dev_desc) },
	{ "8086228A", LPSS_ADDR(bsw_uart_dev_desc) },
	{ "8086228E", LPSS_ADDR(bsw_spi_dev_desc) },
	{ "808622C1", LPSS_ADDR(bsw_i2c_dev_desc) },

	/* Broadwell LPSS devices */
	{ "INT3430", LPSS_ADDR(lpt_dev_desc) },
	{ "INT3431", LPSS_ADDR(lpt_dev_desc) },
	{ "INT3432", LPSS_ADDR(lpt_i2c_dev_desc) },
	{ "INT3433", LPSS_ADDR(lpt_i2c_dev_desc) },
	{ "INT3434", LPSS_ADDR(lpt_uart_dev_desc) },
	{ "INT3435", LPSS_ADDR(lpt_uart_dev_desc) },
	{ "INT3436", LPSS_ADDR(lpt_sdio_dev_desc) },
	{ "INT3437", },

	/* Wildcat Point LPSS devices */
	{ "INT3438", LPSS_ADDR(lpt_dev_desc) },

	{ }
};

#ifdef CONFIG_X86_INTEL_LPSS

static int is_memory(struct acpi_resource *res, void *not_used)
{
	struct resource r;
	return !acpi_dev_resource_memory(res, &r);
}

/* LPSS main clock device. */
static struct platform_device *lpss_clk_dev;

static inline void lpt_register_clock_device(void)
{
	lpss_clk_dev = platform_device_register_simple("clk-lpt", -1, NULL, 0);
}

static int register_device_clock(struct acpi_device *adev,
				 struct lpss_private_data *pdata)
{
	const struct lpss_device_desc *dev_desc = pdata->dev_desc;
	const char *devname = dev_name(&adev->dev);
	struct clk *clk;
	struct lpss_clk_data *clk_data;
	const char *parent, *clk_name;
	void __iomem *prv_base;

	if (!lpss_clk_dev)
		lpt_register_clock_device();

	clk_data = platform_get_drvdata(lpss_clk_dev);
	if (!clk_data)
		return -ENODEV;
	clk = clk_data->clk;

	if (!pdata->mmio_base
	    || pdata->mmio_size < dev_desc->prv_offset + LPSS_CLK_SIZE)
		return -ENODATA;

	parent = clk_data->name;
	prv_base = pdata->mmio_base + dev_desc->prv_offset;

	if (pdata->fixed_clk_rate) {
		clk = clk_register_fixed_rate(NULL, devname, parent, 0,
					      pdata->fixed_clk_rate);
		goto out;
	}

	if (dev_desc->flags & LPSS_CLK_GATE) {
		clk = clk_register_gate(NULL, devname, parent, 0,
					prv_base, 0, 0, NULL);
		parent = devname;
	}

	if (dev_desc->flags & LPSS_CLK_DIVIDER) {
		/* Prevent division by zero */
		if (!readl(prv_base))
			writel(LPSS_CLK_DIVIDER_DEF_MASK, prv_base);

		clk_name = kasprintf(GFP_KERNEL, "%s-div", devname);
		if (!clk_name)
			return -ENOMEM;
		clk = clk_register_fractional_divider(NULL, clk_name, parent,
						      0, prv_base,
						      1, 15, 16, 15, 0, NULL);
		parent = clk_name;

		clk_name = kasprintf(GFP_KERNEL, "%s-update", devname);
		if (!clk_name) {
			kfree(parent);
			return -ENOMEM;
		}
		clk = clk_register_gate(NULL, clk_name, parent,
					CLK_SET_RATE_PARENT | CLK_SET_RATE_GATE,
					prv_base, 31, 0, NULL);
		kfree(parent);
		kfree(clk_name);
	}
out:
	if (IS_ERR(clk))
		return PTR_ERR(clk);

	pdata->clk = clk;
	clk_register_clkdev(clk, dev_desc->clk_con_id, devname);
	return 0;
}

struct lpss_device_links {
	const char *supplier_hid;
	const char *supplier_uid;
	const char *consumer_hid;
	const char *consumer_uid;
	u32 flags;
};

/*
 * The _DEP method is used to identify dependencies but instead of creating
 * device links for every handle in _DEP, only links in the following list are
 * created. That is necessary because, in the general case, _DEP can refer to
 * devices that might not have drivers, or that are on different buses, or where
 * the supplier is not enumerated until after the consumer is probed.
 */
static const struct lpss_device_links lpss_device_links[] = {
	{"808622C1", "7", "80860F14", "3", DL_FLAG_PM_RUNTIME},
};

static bool hid_uid_match(const char *hid1, const char *uid1,
			  const char *hid2, const char *uid2)
{
	return !strcmp(hid1, hid2) && uid1 && uid2 && !strcmp(uid1, uid2);
}

static bool acpi_lpss_is_supplier(struct acpi_device *adev,
				  const struct lpss_device_links *link)
{
	return hid_uid_match(acpi_device_hid(adev), acpi_device_uid(adev),
			     link->supplier_hid, link->supplier_uid);
}

static bool acpi_lpss_is_consumer(struct acpi_device *adev,
				  const struct lpss_device_links *link)
{
	return hid_uid_match(acpi_device_hid(adev), acpi_device_uid(adev),
			     link->consumer_hid, link->consumer_uid);
}

struct hid_uid {
	const char *hid;
	const char *uid;
};

static int match_hid_uid(struct device *dev, void *data)
{
	struct acpi_device *adev = ACPI_COMPANION(dev);
	struct hid_uid *id = data;

	if (!adev)
		return 0;

	return hid_uid_match(acpi_device_hid(adev), acpi_device_uid(adev),
			     id->hid, id->uid);
}

static struct device *acpi_lpss_find_device(const char *hid, const char *uid)
{
	struct hid_uid data = {
		.hid = hid,
		.uid = uid,
	};

	return bus_find_device(&platform_bus_type, NULL, &data, match_hid_uid);
}

static bool acpi_lpss_dep(struct acpi_device *adev, acpi_handle handle)
{
	struct acpi_handle_list dep_devices;
	acpi_status status;
	int i;

	if (!acpi_has_method(adev->handle, "_DEP"))
		return false;

	status = acpi_evaluate_reference(adev->handle, "_DEP", NULL,
					 &dep_devices);
	if (ACPI_FAILURE(status)) {
		dev_dbg(&adev->dev, "Failed to evaluate _DEP.\n");
		return false;
	}

	for (i = 0; i < dep_devices.count; i++) {
		if (dep_devices.handles[i] == handle)
			return true;
	}

	return false;
}

static void acpi_lpss_link_consumer(struct device *dev1,
				    const struct lpss_device_links *link)
{
	struct device *dev2;

	dev2 = acpi_lpss_find_device(link->consumer_hid, link->consumer_uid);
	if (!dev2)
		return;

	if (acpi_lpss_dep(ACPI_COMPANION(dev2), ACPI_HANDLE(dev1)))
		device_link_add(dev2, dev1, link->flags);

	put_device(dev2);
}

static void acpi_lpss_link_supplier(struct device *dev1,
				    const struct lpss_device_links *link)
{
	struct device *dev2;

	dev2 = acpi_lpss_find_device(link->supplier_hid, link->supplier_uid);
	if (!dev2)
		return;

	if (acpi_lpss_dep(ACPI_COMPANION(dev1), ACPI_HANDLE(dev2)))
		device_link_add(dev1, dev2, link->flags);

	put_device(dev2);
}

static void acpi_lpss_create_device_links(struct acpi_device *adev,
					  struct platform_device *pdev)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(lpss_device_links); i++) {
		const struct lpss_device_links *link = &lpss_device_links[i];

		if (acpi_lpss_is_supplier(adev, link))
			acpi_lpss_link_consumer(&pdev->dev, link);

		if (acpi_lpss_is_consumer(adev, link))
			acpi_lpss_link_supplier(&pdev->dev, link);
	}
}

static int acpi_lpss_create_device(struct acpi_device *adev,
				   const struct acpi_device_id *id)
{
	const struct lpss_device_desc *dev_desc;
	struct lpss_private_data *pdata;
	struct resource_entry *rentry;
	struct list_head resource_list;
	struct platform_device *pdev;
	int ret;

	dev_desc = (const struct lpss_device_desc *)id->driver_data;
	if (!dev_desc) {
		pdev = acpi_create_platform_device(adev, NULL);
		return IS_ERR_OR_NULL(pdev) ? PTR_ERR(pdev) : 1;
	}
	pdata = kzalloc(sizeof(*pdata), GFP_KERNEL);
	if (!pdata)
		return -ENOMEM;

	INIT_LIST_HEAD(&resource_list);
	ret = acpi_dev_get_resources(adev, &resource_list, is_memory, NULL);
	if (ret < 0)
		goto err_out;

	list_for_each_entry(rentry, &resource_list, node)
		if (resource_type(rentry->res) == IORESOURCE_MEM) {
			if (dev_desc->prv_size_override)
				pdata->mmio_size = dev_desc->prv_size_override;
			else
				pdata->mmio_size = resource_size(rentry->res);
			pdata->mmio_base = ioremap(rentry->res->start,
						   pdata->mmio_size);
			break;
		}

	acpi_dev_free_resource_list(&resource_list);

	if (!pdata->mmio_base) {
		/* Avoid acpi_bus_attach() instantiating a pdev for this dev. */
		adev->pnp.type.platform_id = 0;
		/* Skip the device, but continue the namespace scan. */
		ret = 0;
		goto err_out;
	}

	pdata->adev = adev;
	pdata->dev_desc = dev_desc;

	if (dev_desc->setup)
		dev_desc->setup(pdata);

	if (dev_desc->flags & LPSS_CLK) {
		ret = register_device_clock(adev, pdata);
		if (ret) {
			/* Skip the device, but continue the namespace scan. */
			ret = 0;
			goto err_out;
		}
	}

	/*
	 * This works around a known issue in ACPI tables where LPSS devices
	 * have _PS0 and _PS3 without _PSC (and no power resources), so
	 * acpi_bus_init_power() will assume that the BIOS has put them into D0.
	 */
	ret = acpi_device_fix_up_power(adev);
	if (ret) {
		/* Skip the device, but continue the namespace scan. */
		ret = 0;
		goto err_out;
	}

	adev->driver_data = pdata;
	pdev = acpi_create_platform_device(adev, dev_desc->properties);
	if (!IS_ERR_OR_NULL(pdev)) {
		acpi_lpss_create_device_links(adev, pdev);
		return 1;
	}

	ret = PTR_ERR(pdev);
	adev->driver_data = NULL;

 err_out:
	kfree(pdata);
	return ret;
}

static u32 __lpss_reg_read(struct lpss_private_data *pdata, unsigned int reg)
{
	return readl(pdata->mmio_base + pdata->dev_desc->prv_offset + reg);
}

static void __lpss_reg_write(u32 val, struct lpss_private_data *pdata,
			     unsigned int reg)
{
	writel(val, pdata->mmio_base + pdata->dev_desc->prv_offset + reg);
}

static int lpss_reg_read(struct device *dev, unsigned int reg, u32 *val)
{
	struct acpi_device *adev;
	struct lpss_private_data *pdata;
	unsigned long flags;
	int ret;

	ret = acpi_bus_get_device(ACPI_HANDLE(dev), &adev);
	if (WARN_ON(ret))
		return ret;

	spin_lock_irqsave(&dev->power.lock, flags);
	if (pm_runtime_suspended(dev)) {
		ret = -EAGAIN;
		goto out;
	}
	pdata = acpi_driver_data(adev);
	if (WARN_ON(!pdata || !pdata->mmio_base)) {
		ret = -ENODEV;
		goto out;
	}
	*val = __lpss_reg_read(pdata, reg);

 out:
	spin_unlock_irqrestore(&dev->power.lock, flags);
	return ret;
}

static ssize_t lpss_ltr_show(struct device *dev, struct device_attribute *attr,
			     char *buf)
{
	u32 ltr_value = 0;
	unsigned int reg;
	int ret;

	reg = strcmp(attr->attr.name, "auto_ltr") ? LPSS_SW_LTR : LPSS_AUTO_LTR;
	ret = lpss_reg_read(dev, reg, &ltr_value);
	if (ret)
		return ret;

	return snprintf(buf, PAGE_SIZE, "%08x\n", ltr_value);
}

static ssize_t lpss_ltr_mode_show(struct device *dev,
				  struct device_attribute *attr, char *buf)
{
	u32 ltr_mode = 0;
	char *outstr;
	int ret;

	ret = lpss_reg_read(dev, LPSS_GENERAL, &ltr_mode);
	if (ret)
		return ret;

	outstr = (ltr_mode & LPSS_GENERAL_LTR_MODE_SW) ? "sw" : "auto";
	return sprintf(buf, "%s\n", outstr);
}

static DEVICE_ATTR(auto_ltr, S_IRUSR, lpss_ltr_show, NULL);
static DEVICE_ATTR(sw_ltr, S_IRUSR, lpss_ltr_show, NULL);
static DEVICE_ATTR(ltr_mode, S_IRUSR, lpss_ltr_mode_show, NULL);

static struct attribute *lpss_attrs[] = {
	&dev_attr_auto_ltr.attr,
	&dev_attr_sw_ltr.attr,
	&dev_attr_ltr_mode.attr,
	NULL,
};

static const struct attribute_group lpss_attr_group = {
	.attrs = lpss_attrs,
	.name = "lpss_ltr",
};

static void acpi_lpss_set_ltr(struct device *dev, s32 val)
{
	struct lpss_private_data *pdata = acpi_driver_data(ACPI_COMPANION(dev));
	u32 ltr_mode, ltr_val;

	ltr_mode = __lpss_reg_read(pdata, LPSS_GENERAL);
	if (val < 0) {
		if (ltr_mode & LPSS_GENERAL_LTR_MODE_SW) {
			ltr_mode &= ~LPSS_GENERAL_LTR_MODE_SW;
			__lpss_reg_write(ltr_mode, pdata, LPSS_GENERAL);
		}
		return;
	}
	ltr_val = __lpss_reg_read(pdata, LPSS_SW_LTR) & ~LPSS_LTR_SNOOP_MASK;
	if (val >= LPSS_LTR_SNOOP_LAT_CUTOFF) {
		ltr_val |= LPSS_LTR_SNOOP_LAT_32US;
		val = LPSS_LTR_MAX_VAL;
	} else if (val > LPSS_LTR_MAX_VAL) {
		ltr_val |= LPSS_LTR_SNOOP_LAT_32US | LPSS_LTR_SNOOP_REQ;
		val >>= LPSS_LTR_SNOOP_LAT_SHIFT;
	} else {
		ltr_val |= LPSS_LTR_SNOOP_LAT_1US | LPSS_LTR_SNOOP_REQ;
	}
	ltr_val |= val;
	__lpss_reg_write(ltr_val, pdata, LPSS_SW_LTR);
	if (!(ltr_mode & LPSS_GENERAL_LTR_MODE_SW)) {
		ltr_mode |= LPSS_GENERAL_LTR_MODE_SW;
		__lpss_reg_write(ltr_mode, pdata, LPSS_GENERAL);
	}
}

#ifdef CONFIG_PM
/**
 * acpi_lpss_save_ctx() - Save the private registers of LPSS device
 * @dev: LPSS device
 * @pdata: pointer to the private data of the LPSS device
 *
 * Most LPSS devices have private registers which may loose their context when
 * the device is powered down. acpi_lpss_save_ctx() saves those registers into
 * prv_reg_ctx array.
 */
static void acpi_lpss_save_ctx(struct device *dev,
			       struct lpss_private_data *pdata)
{
	unsigned int i;

	for (i = 0; i < LPSS_PRV_REG_COUNT; i++) {
		unsigned long offset = i * sizeof(u32);

		pdata->prv_reg_ctx[i] = __lpss_reg_read(pdata, offset);
		dev_dbg(dev, "saving 0x%08x from LPSS reg at offset 0x%02lx\n",
			pdata->prv_reg_ctx[i], offset);
	}
}

/**
 * acpi_lpss_restore_ctx() - Restore the private registers of LPSS device
 * @dev: LPSS device
 * @pdata: pointer to the private data of the LPSS device
 *
 * Restores the registers that were previously stored with acpi_lpss_save_ctx().
 */
static void acpi_lpss_restore_ctx(struct device *dev,
				  struct lpss_private_data *pdata)
{
	unsigned int i;

	for (i = 0; i < LPSS_PRV_REG_COUNT; i++) {
		unsigned long offset = i * sizeof(u32);

		__lpss_reg_write(pdata->prv_reg_ctx[i], pdata, offset);
		dev_dbg(dev, "restoring 0x%08x to LPSS reg at offset 0x%02lx\n",
			pdata->prv_reg_ctx[i], offset);
	}
}

static void acpi_lpss_d3_to_d0_delay(struct lpss_private_data *pdata)
{
	/*
	 * The following delay is needed or the subsequent write operations may
	 * fail. The LPSS devices are actually PCI devices and the PCI spec
	 * expects 10ms delay before the device can be accessed after D3 to D0
	 * transition. However some platforms like BSW does not need this delay.
	 */
	unsigned int delay = 10;	/* default 10ms delay */

	if (pdata->dev_desc->flags & LPSS_NO_D3_DELAY)
		delay = 0;

	msleep(delay);
}

static int acpi_lpss_activate(struct device *dev)
{
	struct lpss_private_data *pdata = acpi_driver_data(ACPI_COMPANION(dev));
	int ret;

	ret = acpi_dev_resume(dev);
	if (ret)
		return ret;

	acpi_lpss_d3_to_d0_delay(pdata);

	/*
	 * This is called only on ->probe() stage where a device is either in
	 * known state defined by BIOS or most likely powered off. Due to this
	 * we have to deassert reset line to be sure that ->probe() will
	 * recognize the device.
	 */
	if (pdata->dev_desc->flags & LPSS_SAVE_CTX)
		lpss_deassert_reset(pdata);

	return 0;
}

static void acpi_lpss_dismiss(struct device *dev)
{
	acpi_dev_suspend(dev, false);
}

/* IOSF SB for LPSS island */
#define LPSS_IOSF_UNIT_LPIOEP		0xA0
#define LPSS_IOSF_UNIT_LPIO1		0xAB
#define LPSS_IOSF_UNIT_LPIO2		0xAC

#define LPSS_IOSF_PMCSR			0x84
#define LPSS_PMCSR_D0			0
#define LPSS_PMCSR_D3hot		3
#define LPSS_PMCSR_Dx_MASK		GENMASK(1, 0)

#define LPSS_IOSF_GPIODEF0		0x154
#define LPSS_GPIODEF0_DMA1_D3		BIT(2)
#define LPSS_GPIODEF0_DMA2_D3		BIT(3)
#define LPSS_GPIODEF0_DMA_D3_MASK	GENMASK(3, 2)
#define LPSS_GPIODEF0_DMA_LLP		BIT(13)

static DEFINE_MUTEX(lpss_iosf_mutex);

static void lpss_iosf_enter_d3_state(void)
{
	u32 value1 = 0;
	u32 mask1 = LPSS_GPIODEF0_DMA_D3_MASK | LPSS_GPIODEF0_DMA_LLP;
	u32 value2 = LPSS_PMCSR_D3hot;
	u32 mask2 = LPSS_PMCSR_Dx_MASK;
	/*
	 * PMC provides an information about actual status of the LPSS devices.
	 * Here we read the values related to LPSS power island, i.e. LPSS
	 * devices, excluding both LPSS DMA controllers, along with SCC domain.
	 */
	u32 func_dis, d3_sts_0, pmc_status, pmc_mask = 0xfe000ffe;
	int ret;

	ret = pmc_atom_read(PMC_FUNC_DIS, &func_dis);
	if (ret)
		return;

	mutex_lock(&lpss_iosf_mutex);

	ret = pmc_atom_read(PMC_D3_STS_0, &d3_sts_0);
	if (ret)
		goto exit;

	/*
	 * Get the status of entire LPSS power island per device basis.
	 * Shutdown both LPSS DMA controllers if and only if all other devices
	 * are already in D3hot.
	 */
	pmc_status = (~(d3_sts_0 | func_dis)) & pmc_mask;
	if (pmc_status)
		goto exit;

	iosf_mbi_modify(LPSS_IOSF_UNIT_LPIO1, MBI_CFG_WRITE,
			LPSS_IOSF_PMCSR, value2, mask2);

	iosf_mbi_modify(LPSS_IOSF_UNIT_LPIO2, MBI_CFG_WRITE,
			LPSS_IOSF_PMCSR, value2, mask2);

	iosf_mbi_modify(LPSS_IOSF_UNIT_LPIOEP, MBI_CR_WRITE,
			LPSS_IOSF_GPIODEF0, value1, mask1);
exit:
	mutex_unlock(&lpss_iosf_mutex);
}

static void lpss_iosf_exit_d3_state(void)
{
	u32 value1 = LPSS_GPIODEF0_DMA1_D3 | LPSS_GPIODEF0_DMA2_D3 |
		     LPSS_GPIODEF0_DMA_LLP;
	u32 mask1 = LPSS_GPIODEF0_DMA_D3_MASK | LPSS_GPIODEF0_DMA_LLP;
	u32 value2 = LPSS_PMCSR_D0;
	u32 mask2 = LPSS_PMCSR_Dx_MASK;

	mutex_lock(&lpss_iosf_mutex);

	iosf_mbi_modify(LPSS_IOSF_UNIT_LPIOEP, MBI_CR_WRITE,
			LPSS_IOSF_GPIODEF0, value1, mask1);

	iosf_mbi_modify(LPSS_IOSF_UNIT_LPIO2, MBI_CFG_WRITE,
			LPSS_IOSF_PMCSR, value2, mask2);

	iosf_mbi_modify(LPSS_IOSF_UNIT_LPIO1, MBI_CFG_WRITE,
			LPSS_IOSF_PMCSR, value2, mask2);

	mutex_unlock(&lpss_iosf_mutex);
}

static int acpi_lpss_suspend(struct device *dev, bool wakeup)
{
	struct lpss_private_data *pdata = acpi_driver_data(ACPI_COMPANION(dev));
	int ret;

	if (pdata->dev_desc->flags & LPSS_SAVE_CTX)
		acpi_lpss_save_ctx(dev, pdata);

	ret = acpi_dev_suspend(dev, wakeup);

	/*
	 * This call must be last in the sequence, otherwise PMC will return
	 * wrong status for devices being about to be powered off. See
	 * lpss_iosf_enter_d3_state() for further information.
	 */
	if (lpss_quirks & LPSS_QUIRK_ALWAYS_POWER_ON && iosf_mbi_available())
		lpss_iosf_enter_d3_state();

	return ret;
}

static int acpi_lpss_resume(struct device *dev)
{
	struct lpss_private_data *pdata = acpi_driver_data(ACPI_COMPANION(dev));
	int ret;

	/*
	 * This call is kept first to be in symmetry with
	 * acpi_lpss_runtime_suspend() one.
	 */
	if (lpss_quirks & LPSS_QUIRK_ALWAYS_POWER_ON && iosf_mbi_available())
		lpss_iosf_exit_d3_state();

	ret = acpi_dev_resume(dev);
	if (ret)
		return ret;

	acpi_lpss_d3_to_d0_delay(pdata);

	if (pdata->dev_desc->flags & LPSS_SAVE_CTX)
		acpi_lpss_restore_ctx(dev, pdata);

	return 0;
}

#ifdef CONFIG_PM_SLEEP
static int acpi_lpss_suspend_late(struct device *dev)
{
	int ret;

	if (dev_pm_smart_suspend_and_suspended(dev))
		return 0;

	ret = pm_generic_suspend_late(dev);
	return ret ? ret : acpi_lpss_suspend(dev, device_may_wakeup(dev));
}

static int acpi_lpss_resume_early(struct device *dev)
{
	int ret = acpi_lpss_resume(dev);

	return ret ? ret : pm_generic_resume_early(dev);
}
#endif /* CONFIG_PM_SLEEP */

static int acpi_lpss_runtime_suspend(struct device *dev)
{
	int ret = pm_generic_runtime_suspend(dev);

	return ret ? ret : acpi_lpss_suspend(dev, true);
}

static int acpi_lpss_runtime_resume(struct device *dev)
{
	int ret = acpi_lpss_resume(dev);

	return ret ? ret : pm_generic_runtime_resume(dev);
}
#endif /* CONFIG_PM */

static struct dev_pm_domain acpi_lpss_pm_domain = {
#ifdef CONFIG_PM
	.activate = acpi_lpss_activate,
	.dismiss = acpi_lpss_dismiss,
#endif
	.ops = {
#ifdef CONFIG_PM
#ifdef CONFIG_PM_SLEEP
		.prepare = acpi_subsys_prepare,
		.complete = acpi_subsys_complete,
		.suspend = acpi_subsys_suspend,
		.suspend_late = acpi_lpss_suspend_late,
		.suspend_noirq = acpi_subsys_suspend_noirq,
		.resume_noirq = acpi_subsys_resume_noirq,
		.resume_early = acpi_lpss_resume_early,
		.freeze = acpi_subsys_freeze,
		.freeze_late = acpi_subsys_freeze_late,
		.freeze_noirq = acpi_subsys_freeze_noirq,
		.thaw_noirq = acpi_subsys_thaw_noirq,
		.poweroff = acpi_subsys_suspend,
		.poweroff_late = acpi_lpss_suspend_late,
		.poweroff_noirq = acpi_subsys_suspend_noirq,
		.restore_noirq = acpi_subsys_resume_noirq,
		.restore_early = acpi_lpss_resume_early,
#endif
		.runtime_suspend = acpi_lpss_runtime_suspend,
		.runtime_resume = acpi_lpss_runtime_resume,
#endif
	},
};

static int acpi_lpss_platform_notify(struct notifier_block *nb,
				     unsigned long action, void *data)
{
	struct platform_device *pdev = to_platform_device(data);
	struct lpss_private_data *pdata;
	struct acpi_device *adev;
	const struct acpi_device_id *id;

	id = acpi_match_device(acpi_lpss_device_ids, &pdev->dev);
	if (!id || !id->driver_data)
		return 0;

	if (acpi_bus_get_device(ACPI_HANDLE(&pdev->dev), &adev))
		return 0;

	pdata = acpi_driver_data(adev);
	if (!pdata)
		return 0;

	if (pdata->mmio_base &&
	    pdata->mmio_size < pdata->dev_desc->prv_offset + LPSS_LTR_SIZE) {
		dev_err(&pdev->dev, "MMIO size insufficient to access LTR\n");
		return 0;
	}

	switch (action) {
	case BUS_NOTIFY_BIND_DRIVER:
		dev_pm_domain_set(&pdev->dev, &acpi_lpss_pm_domain);
		break;
	case BUS_NOTIFY_DRIVER_NOT_BOUND:
	case BUS_NOTIFY_UNBOUND_DRIVER:
		dev_pm_domain_set(&pdev->dev, NULL);
		break;
	case BUS_NOTIFY_ADD_DEVICE:
		dev_pm_domain_set(&pdev->dev, &acpi_lpss_pm_domain);
		if (pdata->dev_desc->flags & LPSS_LTR)
			return sysfs_create_group(&pdev->dev.kobj,
						  &lpss_attr_group);
		break;
	case BUS_NOTIFY_DEL_DEVICE:
		if (pdata->dev_desc->flags & LPSS_LTR)
			sysfs_remove_group(&pdev->dev.kobj, &lpss_attr_group);
		dev_pm_domain_set(&pdev->dev, NULL);
		break;
	default:
		break;
	}

	return 0;
}

static struct notifier_block acpi_lpss_nb = {
	.notifier_call = acpi_lpss_platform_notify,
};

static void acpi_lpss_bind(struct device *dev)
{
	struct lpss_private_data *pdata = acpi_driver_data(ACPI_COMPANION(dev));

	if (!pdata || !pdata->mmio_base || !(pdata->dev_desc->flags & LPSS_LTR))
		return;

	if (pdata->mmio_size >= pdata->dev_desc->prv_offset + LPSS_LTR_SIZE)
		dev->power.set_latency_tolerance = acpi_lpss_set_ltr;
	else
		dev_err(dev, "MMIO size insufficient to access LTR\n");
}

static void acpi_lpss_unbind(struct device *dev)
{
	dev->power.set_latency_tolerance = NULL;
}

static struct acpi_scan_handler lpss_handler = {
	.ids = acpi_lpss_device_ids,
	.attach = acpi_lpss_create_device,
	.bind = acpi_lpss_bind,
	.unbind = acpi_lpss_unbind,
};

void __init acpi_lpss_init(void)
{
	const struct x86_cpu_id *id;
	int ret;

	ret = lpt_clk_init();
	if (ret)
		return;

	id = x86_match_cpu(lpss_cpu_ids);
	if (id)
		lpss_quirks |= LPSS_QUIRK_ALWAYS_POWER_ON;

	bus_register_notifier(&platform_bus_type, &acpi_lpss_nb);
	acpi_scan_add_handler(&lpss_handler);
}

#else

static struct acpi_scan_handler lpss_handler = {
	.ids = acpi_lpss_device_ids,
};

void __init acpi_lpss_init(void)
{
	acpi_scan_add_handler(&lpss_handler);
}

#endif /* CONFIG_X86_INTEL_LPSS */