drivers/acpi/acpi_lpss.c - linux - Git at Google

 /*
  * 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/clk.h>
 #include <linux/clkdev.h>
 #include <linux/clk-provider.h>
 #include <linux/err.h>
 #include <linux/io.h>
 #include <linux/platform_device.h>
 #include <linux/platform_data/clk-lpss.h>
 #include <linux/pm_runtime.h>

 #include "internal.h"

 ACPI_MODULE_NAME("acpi_lpss");

 #define LPSS_CLK_SIZE	0x04
 #define LPSS_LTR_SIZE	0x18

 /* Offsets relative to LPSS_PRIVATE_OFFSET */
 #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_TX_INT			0x20
 #define LPSS_TX_INT_MASK		BIT(1)

 struct lpss_shared_clock {
 	const char *name;
 	unsigned long rate;
 	struct clk *clk;
 };

 struct lpss_private_data;

 struct lpss_device_desc {
 	bool clk_required;
 	const char *clkdev_name;
 	bool ltr_required;
 	unsigned int prv_offset;
 	size_t prv_size_override;
 	bool clk_gate;
 	struct lpss_shared_clock *shared_clock;
 	void (*setup)(struct lpss_private_data *pdata);
 };

 static struct lpss_device_desc lpss_dma_desc = {
 	.clk_required = true,
 	.clkdev_name = "hclk",
 };

 struct lpss_private_data {
 	void __iomem *mmio_base;
 	resource_size_t mmio_size;
 	struct clk *clk;
 	const struct lpss_device_desc *dev_desc;
 };

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

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

 	offset = pdata->dev_desc->prv_offset + LPSS_GENERAL;
 	reg = readl(pdata->mmio_base + offset);
 	writel(reg | LPSS_GENERAL_UART_RTS_OVRD, pdata->mmio_base + offset);
 }

 static struct lpss_device_desc lpt_dev_desc = {
 	.clk_required = true,
 	.prv_offset = 0x800,
 	.ltr_required = true,
 	.clk_gate = true,
 };

 static struct lpss_device_desc lpt_uart_dev_desc = {
 	.clk_required = true,
 	.prv_offset = 0x800,
 	.ltr_required = true,
 	.clk_gate = true,
 	.setup = lpss_uart_setup,
 };

 static struct lpss_device_desc lpt_sdio_dev_desc = {
 	.prv_offset = 0x1000,
 	.prv_size_override = 0x1018,
 	.ltr_required = true,
 };

 static struct lpss_shared_clock uart_clock = {
 	.name = "uart_clk",
 	.rate = 44236800,
 };

 static struct lpss_device_desc byt_uart_dev_desc = {
 	.clk_required = true,
 	.prv_offset = 0x800,
 	.clk_gate = true,
 	.shared_clock = &uart_clock,
 	.setup = lpss_uart_setup,
 };

 static struct lpss_shared_clock spi_clock = {
 	.name = "spi_clk",
 	.rate = 50000000,
 };

 static struct lpss_device_desc byt_spi_dev_desc = {
 	.clk_required = true,
 	.prv_offset = 0x400,
 	.clk_gate = true,
 	.shared_clock = &spi_clock,
 };

 static struct lpss_device_desc byt_sdio_dev_desc = {
 	.clk_required = true,
 };

 static struct lpss_shared_clock i2c_clock = {
 	.name = "i2c_clk",
 	.rate = 100000000,
 };

 static struct lpss_device_desc byt_i2c_dev_desc = {
 	.clk_required = true,
 	.prv_offset = 0x800,
 	.shared_clock = &i2c_clock,
 };

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

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

 	/* BayTrail LPSS devices */
 	{ "80860F0A", (unsigned long)&byt_uart_dev_desc },
 	{ "80860F0E", (unsigned long)&byt_spi_dev_desc },
 	{ "80860F14", (unsigned long)&byt_sdio_dev_desc },
 	{ "80860F41", (unsigned long)&byt_i2c_dev_desc },
 	{ "INT33B2", },

 	{ "INT3430", (unsigned long)&lpt_dev_desc },
 	{ "INT3431", (unsigned long)&lpt_dev_desc },
 	{ "INT3432", (unsigned long)&lpt_dev_desc },
 	{ "INT3433", (unsigned long)&lpt_dev_desc },
 	{ "INT3434", (unsigned long)&lpt_uart_dev_desc },
 	{ "INT3435", (unsigned long)&lpt_uart_dev_desc },
 	{ "INT3436", (unsigned long)&lpt_sdio_dev_desc },
 	{ "INT3437", },

 	{ }
 };

 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;
 	struct lpss_shared_clock *shared_clock = dev_desc->shared_clock;
 	struct clk *clk = ERR_PTR(-ENODEV);
 	struct lpss_clk_data *clk_data;
 	const char *parent;

 	if (!lpss_clk_dev)
 		lpt_register_clock_device();

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

 	if (dev_desc->clkdev_name) {
 		clk_register_clkdev(clk_data->clk, dev_desc->clkdev_name,
 				    dev_name(&adev->dev));
 		return 0;
 	}

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

 	parent = clk_data->name;

 	if (shared_clock) {
 		clk = shared_clock->clk;
 		if (!clk) {
 			clk = clk_register_fixed_rate(NULL, shared_clock->name,
 						      "lpss_clk", 0,
 						      shared_clock->rate);
 			shared_clock->clk = clk;
 		}
 		parent = shared_clock->name;
 	}

 	if (dev_desc->clk_gate) {
 		clk = clk_register_gate(NULL, dev_name(&adev->dev), parent, 0,
 					pdata->mmio_base + dev_desc->prv_offset,
 					0, 0, NULL);
 		pdata->clk = clk;
 	}

 	if (IS_ERR(clk))
 		return PTR_ERR(clk);

 	clk_register_clkdev(clk, NULL, dev_name(&adev->dev));
 	return 0;
 }

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

 	dev_desc = (struct lpss_device_desc *)id->driver_data;
 	if (!dev_desc)
 		return acpi_create_platform_device(adev, id);

 	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);

 	pdata->dev_desc = dev_desc;

 	if (dev_desc->clk_required) {
 		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;
 	}

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

 	adev->driver_data = pdata;
 	ret = acpi_create_platform_device(adev, id);
 	if (ret > 0)
 		return ret;

 	adev->driver_data = NULL;

  err_out:
 	kfree(pdata);
 	return ret;
 }

 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 = readl(pdata->mmio_base + pdata->dev_desc->prv_offset + 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 struct attribute_group lpss_attr_group = {
 	.attrs = lpss_attrs,
 	.name = "lpss_ltr",
 };

 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;
 	int ret = 0;

 	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 || !pdata->mmio_base || !pdata->dev_desc->ltr_required)
 		return 0;

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

 	if (action == BUS_NOTIFY_ADD_DEVICE)
 		ret = sysfs_create_group(&pdev->dev.kobj, &lpss_attr_group);
 	else if (action == BUS_NOTIFY_DEL_DEVICE)
 		sysfs_remove_group(&pdev->dev.kobj, &lpss_attr_group);

 	return ret;
 }

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

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

 void __init acpi_lpss_init(void)
 {
 	if (!lpt_clk_init()) {
 		bus_register_notifier(&platform_bus_type, &acpi_lpss_nb);
 		acpi_scan_add_handler(&lpss_handler);
 	}
 }
	/*
	* 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/clk.h>
	#include <linux/clkdev.h>
	#include <linux/clk-provider.h>
	#include <linux/err.h>
	#include <linux/io.h>
	#include <linux/platform_device.h>
	#include <linux/platform_data/clk-lpss.h>
	#include <linux/pm_runtime.h>

	#include "internal.h"

	ACPI_MODULE_NAME("acpi_lpss");

	#define LPSS_CLK_SIZE 0x04
	#define LPSS_LTR_SIZE 0x18

	/* Offsets relative to LPSS_PRIVATE_OFFSET */
	#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_TX_INT 0x20
	#define LPSS_TX_INT_MASK BIT(1)

	struct lpss_shared_clock {
	const char *name;
	unsigned long rate;
	struct clk *clk;
	};

	struct lpss_private_data;

	struct lpss_device_desc {
	bool clk_required;
	const char *clkdev_name;
	bool ltr_required;
	unsigned int prv_offset;
	size_t prv_size_override;
	bool clk_gate;
	struct lpss_shared_clock *shared_clock;
	void (setup)(struct lpss_private_data pdata);
	};

	static struct lpss_device_desc lpss_dma_desc = {
	.clk_required = true,
	.clkdev_name = "hclk",
	};

	struct lpss_private_data {
	void __iomem *mmio_base;
	resource_size_t mmio_size;
	struct clk *clk;
	const struct lpss_device_desc *dev_desc;
	};

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

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

	offset = pdata->dev_desc->prv_offset + LPSS_GENERAL;
	reg = readl(pdata->mmio_base + offset);
	writel(reg \| LPSS_GENERAL_UART_RTS_OVRD, pdata->mmio_base + offset);
	}

	static struct lpss_device_desc lpt_dev_desc = {
	.clk_required = true,
	.prv_offset = 0x800,
	.ltr_required = true,
	.clk_gate = true,
	};

	static struct lpss_device_desc lpt_uart_dev_desc = {
	.clk_required = true,
	.prv_offset = 0x800,
	.ltr_required = true,
	.clk_gate = true,
	.setup = lpss_uart_setup,
	};

	static struct lpss_device_desc lpt_sdio_dev_desc = {
	.prv_offset = 0x1000,
	.prv_size_override = 0x1018,
	.ltr_required = true,
	};

	static struct lpss_shared_clock uart_clock = {
	.name = "uart_clk",
	.rate = 44236800,
	};

	static struct lpss_device_desc byt_uart_dev_desc = {
	.clk_required = true,
	.prv_offset = 0x800,
	.clk_gate = true,
	.shared_clock = &uart_clock,
	.setup = lpss_uart_setup,
	};

	static struct lpss_shared_clock spi_clock = {
	.name = "spi_clk",
	.rate = 50000000,
	};

	static struct lpss_device_desc byt_spi_dev_desc = {
	.clk_required = true,
	.prv_offset = 0x400,
	.clk_gate = true,
	.shared_clock = &spi_clock,
	};

	static struct lpss_device_desc byt_sdio_dev_desc = {
	.clk_required = true,
	};

	static struct lpss_shared_clock i2c_clock = {
	.name = "i2c_clk",
	.rate = 100000000,
	};

	static struct lpss_device_desc byt_i2c_dev_desc = {
	.clk_required = true,
	.prv_offset = 0x800,
	.shared_clock = &i2c_clock,
	};

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

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

	/* BayTrail LPSS devices */
	{ "80860F0A", (unsigned long)&byt_uart_dev_desc },
	{ "80860F0E", (unsigned long)&byt_spi_dev_desc },
	{ "80860F14", (unsigned long)&byt_sdio_dev_desc },
	{ "80860F41", (unsigned long)&byt_i2c_dev_desc },
	{ "INT33B2", },

	{ "INT3430", (unsigned long)&lpt_dev_desc },
	{ "INT3431", (unsigned long)&lpt_dev_desc },
	{ "INT3432", (unsigned long)&lpt_dev_desc },
	{ "INT3433", (unsigned long)&lpt_dev_desc },
	{ "INT3434", (unsigned long)&lpt_uart_dev_desc },
	{ "INT3435", (unsigned long)&lpt_uart_dev_desc },
	{ "INT3436", (unsigned long)&lpt_sdio_dev_desc },
	{ "INT3437", },

	{ }
	};

	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;
	struct lpss_shared_clock *shared_clock = dev_desc->shared_clock;
	struct clk *clk = ERR_PTR(-ENODEV);
	struct lpss_clk_data *clk_data;
	const char *parent;

	if (!lpss_clk_dev)
	lpt_register_clock_device();

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

	if (dev_desc->clkdev_name) {
	clk_register_clkdev(clk_data->clk, dev_desc->clkdev_name,
	dev_name(&adev->dev));
	return 0;
	}

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

	parent = clk_data->name;

	if (shared_clock) {
	clk = shared_clock->clk;
	if (!clk) {
	clk = clk_register_fixed_rate(NULL, shared_clock->name,
	"lpss_clk", 0,
	shared_clock->rate);
	shared_clock->clk = clk;
	}
	parent = shared_clock->name;
	}

	if (dev_desc->clk_gate) {
	clk = clk_register_gate(NULL, dev_name(&adev->dev), parent, 0,
	pdata->mmio_base + dev_desc->prv_offset,
	0, 0, NULL);
	pdata->clk = clk;
	}

	if (IS_ERR(clk))
	return PTR_ERR(clk);

	clk_register_clkdev(clk, NULL, dev_name(&adev->dev));
	return 0;
	}

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

	dev_desc = (struct lpss_device_desc *)id->driver_data;
	if (!dev_desc)
	return acpi_create_platform_device(adev, id);

	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);

	pdata->dev_desc = dev_desc;

	if (dev_desc->clk_required) {
	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;
	}

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

	adev->driver_data = pdata;
	ret = acpi_create_platform_device(adev, id);
	if (ret > 0)
	return ret;

	adev->driver_data = NULL;

	err_out:
	kfree(pdata);
	return ret;
	}

	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 = readl(pdata->mmio_base + pdata->dev_desc->prv_offset + 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 struct attribute_group lpss_attr_group = {
	.attrs = lpss_attrs,
	.name = "lpss_ltr",
	};

	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;
	int ret = 0;

	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 \|\| !pdata->mmio_base \|\| !pdata->dev_desc->ltr_required)
	return 0;

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

	if (action == BUS_NOTIFY_ADD_DEVICE)
	ret = sysfs_create_group(&pdev->dev.kobj, &lpss_attr_group);
	else if (action == BUS_NOTIFY_DEL_DEVICE)
	sysfs_remove_group(&pdev->dev.kobj, &lpss_attr_group);

	return ret;
	}

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

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

	void __init acpi_lpss_init(void)
	{
	if (!lpt_clk_init()) {
	bus_register_notifier(&platform_bus_type, &acpi_lpss_nb);
	acpi_scan_add_handler(&lpss_handler);
	}
	}