drivers/watchdog/aspeed_wdt.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Copyright 2016 IBM Corporation
  *
  * Joel Stanley <joel@jms.id.au>
  */

 #include <linux/delay.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/watchdog.h>

 static bool nowayout = WATCHDOG_NOWAYOUT;
 module_param(nowayout, bool, 0);
 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
 				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

 struct aspeed_wdt {
 	struct watchdog_device	wdd;
 	void __iomem		*base;
 	u32			ctrl;
 };

 struct aspeed_wdt_config {
 	u32 ext_pulse_width_mask;
 };

 static const struct aspeed_wdt_config ast2400_config = {
 	.ext_pulse_width_mask = 0xff,
 };

 static const struct aspeed_wdt_config ast2500_config = {
 	.ext_pulse_width_mask = 0xfffff,
 };

 static const struct of_device_id aspeed_wdt_of_table[] = {
 	{ .compatible = "aspeed,ast2400-wdt", .data = &ast2400_config },
 	{ .compatible = "aspeed,ast2500-wdt", .data = &ast2500_config },
 	{ .compatible = "aspeed,ast2600-wdt", .data = &ast2500_config },
 	{ },
 };
 MODULE_DEVICE_TABLE(of, aspeed_wdt_of_table);

 #define WDT_STATUS		0x00
 #define WDT_RELOAD_VALUE	0x04
 #define WDT_RESTART		0x08
 #define WDT_CTRL		0x0C
 #define   WDT_CTRL_BOOT_SECONDARY	BIT(7)
 #define   WDT_CTRL_RESET_MODE_SOC	(0x00 << 5)
 #define   WDT_CTRL_RESET_MODE_FULL_CHIP	(0x01 << 5)
 #define   WDT_CTRL_RESET_MODE_ARM_CPU	(0x10 << 5)
 #define   WDT_CTRL_1MHZ_CLK		BIT(4)
 #define   WDT_CTRL_WDT_EXT		BIT(3)
 #define   WDT_CTRL_WDT_INTR		BIT(2)
 #define   WDT_CTRL_RESET_SYSTEM		BIT(1)
 #define   WDT_CTRL_ENABLE		BIT(0)
 #define WDT_TIMEOUT_STATUS	0x10
 #define   WDT_TIMEOUT_STATUS_BOOT_SECONDARY	BIT(1)
 #define WDT_CLEAR_TIMEOUT_STATUS	0x14
 #define   WDT_CLEAR_TIMEOUT_AND_BOOT_CODE_SELECTION	BIT(0)

 /*
  * WDT_RESET_WIDTH controls the characteristics of the external pulse (if
  * enabled), specifically:
  *
  * * Pulse duration
  * * Drive mode: push-pull vs open-drain
  * * Polarity: Active high or active low
  *
  * Pulse duration configuration is available on both the AST2400 and AST2500,
  * though the field changes between SoCs:
  *
  * AST2400: Bits 7:0
  * AST2500: Bits 19:0
  *
  * This difference is captured in struct aspeed_wdt_config.
  *
  * The AST2500 exposes the drive mode and polarity options, but not in a
  * regular fashion. For read purposes, bit 31 represents active high or low,
  * and bit 30 represents push-pull or open-drain. With respect to write, magic
  * values need to be written to the top byte to change the state of the drive
  * mode and polarity bits. Any other value written to the top byte has no
  * effect on the state of the drive mode or polarity bits. However, the pulse
  * width value must be preserved (as desired) if written.
  */
 #define WDT_RESET_WIDTH		0x18
 #define   WDT_RESET_WIDTH_ACTIVE_HIGH	BIT(31)
 #define     WDT_ACTIVE_HIGH_MAGIC	(0xA5 << 24)
 #define     WDT_ACTIVE_LOW_MAGIC	(0x5A << 24)
 #define   WDT_RESET_WIDTH_PUSH_PULL	BIT(30)
 #define     WDT_PUSH_PULL_MAGIC		(0xA8 << 24)
 #define     WDT_OPEN_DRAIN_MAGIC	(0x8A << 24)

 #define WDT_RESTART_MAGIC	0x4755

 /* 32 bits at 1MHz, in milliseconds */
 #define WDT_MAX_TIMEOUT_MS	4294967
 #define WDT_DEFAULT_TIMEOUT	30
 #define WDT_RATE_1MHZ		1000000

 static struct aspeed_wdt *to_aspeed_wdt(struct watchdog_device *wdd)
 {
 	return container_of(wdd, struct aspeed_wdt, wdd);
 }

 static void aspeed_wdt_enable(struct aspeed_wdt *wdt, int count)
 {
 	wdt->ctrl |= WDT_CTRL_ENABLE;

 	writel(0, wdt->base + WDT_CTRL);
 	writel(count, wdt->base + WDT_RELOAD_VALUE);
 	writel(WDT_RESTART_MAGIC, wdt->base + WDT_RESTART);
 	writel(wdt->ctrl, wdt->base + WDT_CTRL);
 }

 static int aspeed_wdt_start(struct watchdog_device *wdd)
 {
 	struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);

 	aspeed_wdt_enable(wdt, wdd->timeout * WDT_RATE_1MHZ);

 	return 0;
 }

 static int aspeed_wdt_stop(struct watchdog_device *wdd)
 {
 	struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);

 	wdt->ctrl &= ~WDT_CTRL_ENABLE;
 	writel(wdt->ctrl, wdt->base + WDT_CTRL);

 	return 0;
 }

 static int aspeed_wdt_ping(struct watchdog_device *wdd)
 {
 	struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);

 	writel(WDT_RESTART_MAGIC, wdt->base + WDT_RESTART);

 	return 0;
 }

 static int aspeed_wdt_set_timeout(struct watchdog_device *wdd,
 				  unsigned int timeout)
 {
 	struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);
 	u32 actual;

 	wdd->timeout = timeout;

 	actual = min(timeout, wdd->max_hw_heartbeat_ms / 1000);

 	writel(actual * WDT_RATE_1MHZ, wdt->base + WDT_RELOAD_VALUE);
 	writel(WDT_RESTART_MAGIC, wdt->base + WDT_RESTART);

 	return 0;
 }

 static int aspeed_wdt_restart(struct watchdog_device *wdd,
 			      unsigned long action, void *data)
 {
 	struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);

 	wdt->ctrl &= ~WDT_CTRL_BOOT_SECONDARY;
 	aspeed_wdt_enable(wdt, 128 * WDT_RATE_1MHZ / 1000);

 	mdelay(1000);

 	return 0;
 }

 /* access_cs0 shows if cs0 is accessible, hence the reverted bit */
 static ssize_t access_cs0_show(struct device *dev,
 			       struct device_attribute *attr, char *buf)
 {
 	struct aspeed_wdt *wdt = dev_get_drvdata(dev);
 	u32 status = readl(wdt->base + WDT_TIMEOUT_STATUS);

 	return sysfs_emit(buf, "%u\n",
 			  !(status & WDT_TIMEOUT_STATUS_BOOT_SECONDARY));
 }

 static ssize_t access_cs0_store(struct device *dev,
 				struct device_attribute *attr, const char *buf,
 				size_t size)
 {
 	struct aspeed_wdt *wdt = dev_get_drvdata(dev);
 	unsigned long val;

 	if (kstrtoul(buf, 10, &val))
 		return -EINVAL;

 	if (val)
 		writel(WDT_CLEAR_TIMEOUT_AND_BOOT_CODE_SELECTION,
 		       wdt->base + WDT_CLEAR_TIMEOUT_STATUS);

 	return size;
 }

 /*
  * This attribute exists only if the system has booted from the alternate
  * flash with 'alt-boot' option.
  *
  * At alternate flash the 'access_cs0' sysfs node provides:
  *   ast2400: a way to get access to the primary SPI flash chip at CS0
  *            after booting from the alternate chip at CS1.
  *   ast2500: a way to restore the normal address mapping from
  *            (CS0->CS1, CS1->CS0) to (CS0->CS0, CS1->CS1).
  *
  * Clearing the boot code selection and timeout counter also resets to the
  * initial state the chip select line mapping. When the SoC is in normal
  * mapping state (i.e. booted from CS0), clearing those bits does nothing for
  * both versions of the SoC. For alternate boot mode (booted from CS1 due to
  * wdt2 expiration) the behavior differs as described above.
  *
  * This option can be used with wdt2 (watchdog1) only.
  */
 static DEVICE_ATTR_RW(access_cs0);

 static struct attribute *bswitch_attrs[] = {
 	&dev_attr_access_cs0.attr,
 	NULL
 };
 ATTRIBUTE_GROUPS(bswitch);

 static const struct watchdog_ops aspeed_wdt_ops = {
 	.start		= aspeed_wdt_start,
 	.stop		= aspeed_wdt_stop,
 	.ping		= aspeed_wdt_ping,
 	.set_timeout	= aspeed_wdt_set_timeout,
 	.restart	= aspeed_wdt_restart,
 	.owner		= THIS_MODULE,
 };

 static const struct watchdog_info aspeed_wdt_info = {
 	.options	= WDIOF_KEEPALIVEPING
 			| WDIOF_MAGICCLOSE
 			| WDIOF_SETTIMEOUT,
 	.identity	= KBUILD_MODNAME,
 };

 static int aspeed_wdt_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	const struct aspeed_wdt_config *config;
 	const struct of_device_id *ofdid;
 	struct aspeed_wdt *wdt;
 	struct device_node *np;
 	const char *reset_type;
 	u32 duration;
 	u32 status;
 	int ret;

 	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
 	if (!wdt)
 		return -ENOMEM;

 	wdt->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(wdt->base))
 		return PTR_ERR(wdt->base);

 	wdt->wdd.info = &aspeed_wdt_info;
 	wdt->wdd.ops = &aspeed_wdt_ops;
 	wdt->wdd.max_hw_heartbeat_ms = WDT_MAX_TIMEOUT_MS;
 	wdt->wdd.parent = dev;

 	wdt->wdd.timeout = WDT_DEFAULT_TIMEOUT;
 	watchdog_init_timeout(&wdt->wdd, 0, dev);

 	watchdog_set_nowayout(&wdt->wdd, nowayout);

 	np = dev->of_node;

 	ofdid = of_match_node(aspeed_wdt_of_table, np);
 	if (!ofdid)
 		return -EINVAL;
 	config = ofdid->data;

 	/*
 	 * On clock rates:
 	 *  - ast2400 wdt can run at PCLK, or 1MHz
 	 *  - ast2500 only runs at 1MHz, hard coding bit 4 to 1
 	 *  - ast2600 always runs at 1MHz
 	 *
 	 * Set the ast2400 to run at 1MHz as it simplifies the driver.
 	 */
 	if (of_device_is_compatible(np, "aspeed,ast2400-wdt"))
 		wdt->ctrl = WDT_CTRL_1MHZ_CLK;

 	/*
 	 * Control reset on a per-device basis to ensure the
 	 * host is not affected by a BMC reboot
 	 */
 	ret = of_property_read_string(np, "aspeed,reset-type", &reset_type);
 	if (ret) {
 		wdt->ctrl |= WDT_CTRL_RESET_MODE_SOC | WDT_CTRL_RESET_SYSTEM;
 	} else {
 		if (!strcmp(reset_type, "cpu"))
 			wdt->ctrl |= WDT_CTRL_RESET_MODE_ARM_CPU |
 				     WDT_CTRL_RESET_SYSTEM;
 		else if (!strcmp(reset_type, "soc"))
 			wdt->ctrl |= WDT_CTRL_RESET_MODE_SOC |
 				     WDT_CTRL_RESET_SYSTEM;
 		else if (!strcmp(reset_type, "system"))
 			wdt->ctrl |= WDT_CTRL_RESET_MODE_FULL_CHIP |
 				     WDT_CTRL_RESET_SYSTEM;
 		else if (strcmp(reset_type, "none"))
 			return -EINVAL;
 	}
 	if (of_property_read_bool(np, "aspeed,external-signal"))
 		wdt->ctrl |= WDT_CTRL_WDT_EXT;
 	if (of_property_read_bool(np, "aspeed,alt-boot"))
 		wdt->ctrl |= WDT_CTRL_BOOT_SECONDARY;

 	if (readl(wdt->base + WDT_CTRL) & WDT_CTRL_ENABLE)  {
 		/*
 		 * The watchdog is running, but invoke aspeed_wdt_start() to
 		 * write wdt->ctrl to WDT_CTRL to ensure the watchdog's
 		 * configuration conforms to the driver's expectations.
 		 * Primarily, ensure we're using the 1MHz clock source.
 		 */
 		aspeed_wdt_start(&wdt->wdd);
 		set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
 	}

 	if ((of_device_is_compatible(np, "aspeed,ast2500-wdt")) ||
 		(of_device_is_compatible(np, "aspeed,ast2600-wdt"))) {
 		u32 reg = readl(wdt->base + WDT_RESET_WIDTH);

 		reg &= config->ext_pulse_width_mask;
 		if (of_property_read_bool(np, "aspeed,ext-active-high"))
 			reg |= WDT_ACTIVE_HIGH_MAGIC;
 		else
 			reg |= WDT_ACTIVE_LOW_MAGIC;

 		writel(reg, wdt->base + WDT_RESET_WIDTH);

 		reg &= config->ext_pulse_width_mask;
 		if (of_property_read_bool(np, "aspeed,ext-push-pull"))
 			reg |= WDT_PUSH_PULL_MAGIC;
 		else
 			reg |= WDT_OPEN_DRAIN_MAGIC;

 		writel(reg, wdt->base + WDT_RESET_WIDTH);
 	}

 	if (!of_property_read_u32(np, "aspeed,ext-pulse-duration", &duration)) {
 		u32 max_duration = config->ext_pulse_width_mask + 1;

 		if (duration == 0 || duration > max_duration) {
 			dev_err(dev, "Invalid pulse duration: %uus\n",
 				duration);
 			duration = max(1U, min(max_duration, duration));
 			dev_info(dev, "Pulse duration set to %uus\n",
 				 duration);
 		}

 		/*
 		 * The watchdog is always configured with a 1MHz source, so
 		 * there is no need to scale the microsecond value. However we
 		 * need to offset it - from the datasheet:
 		 *
 		 * "This register decides the asserting duration of wdt_ext and
 		 * wdt_rstarm signal. The default value is 0xFF. It means the
 		 * default asserting duration of wdt_ext and wdt_rstarm is
 		 * 256us."
 		 *
 		 * This implies a value of 0 gives a 1us pulse.
 		 */
 		writel(duration - 1, wdt->base + WDT_RESET_WIDTH);
 	}

 	status = readl(wdt->base + WDT_TIMEOUT_STATUS);
 	if (status & WDT_TIMEOUT_STATUS_BOOT_SECONDARY) {
 		wdt->wdd.bootstatus = WDIOF_CARDRESET;

 		if (of_device_is_compatible(np, "aspeed,ast2400-wdt") ||
 		    of_device_is_compatible(np, "aspeed,ast2500-wdt"))
 			wdt->wdd.groups = bswitch_groups;
 	}

 	dev_set_drvdata(dev, wdt);

 	return devm_watchdog_register_device(dev, &wdt->wdd);
 }

 static struct platform_driver aspeed_watchdog_driver = {
 	.probe = aspeed_wdt_probe,
 	.driver = {
 		.name = KBUILD_MODNAME,
 		.of_match_table = of_match_ptr(aspeed_wdt_of_table),
 	},
 };

 static int __init aspeed_wdt_init(void)
 {
 	return platform_driver_register(&aspeed_watchdog_driver);
 }
 arch_initcall(aspeed_wdt_init);

 static void __exit aspeed_wdt_exit(void)
 {
 	platform_driver_unregister(&aspeed_watchdog_driver);
 }
 module_exit(aspeed_wdt_exit);

 MODULE_DESCRIPTION("Aspeed Watchdog Driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Copyright 2016 IBM Corporation
	*
	* Joel Stanley <joel@jms.id.au>
	*/

	#include <linux/delay.h>
	#include <linux/io.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/platform_device.h>
	#include <linux/watchdog.h>

	static bool nowayout = WATCHDOG_NOWAYOUT;
	module_param(nowayout, bool, 0);
	MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

	struct aspeed_wdt {
	struct watchdog_device wdd;
	void __iomem *base;
	u32 ctrl;
	};

	struct aspeed_wdt_config {
	u32 ext_pulse_width_mask;
	};

	static const struct aspeed_wdt_config ast2400_config = {
	.ext_pulse_width_mask = 0xff,
	};

	static const struct aspeed_wdt_config ast2500_config = {
	.ext_pulse_width_mask = 0xfffff,
	};

	static const struct of_device_id aspeed_wdt_of_table[] = {
	{ .compatible = "aspeed,ast2400-wdt", .data = &ast2400_config },
	{ .compatible = "aspeed,ast2500-wdt", .data = &ast2500_config },
	{ .compatible = "aspeed,ast2600-wdt", .data = &ast2500_config },
	{ },
	};
	MODULE_DEVICE_TABLE(of, aspeed_wdt_of_table);

	#define WDT_STATUS 0x00
	#define WDT_RELOAD_VALUE 0x04
	#define WDT_RESTART 0x08
	#define WDT_CTRL 0x0C
	#define WDT_CTRL_BOOT_SECONDARY BIT(7)
	#define WDT_CTRL_RESET_MODE_SOC (0x00 << 5)
	#define WDT_CTRL_RESET_MODE_FULL_CHIP (0x01 << 5)
	#define WDT_CTRL_RESET_MODE_ARM_CPU (0x10 << 5)
	#define WDT_CTRL_1MHZ_CLK BIT(4)
	#define WDT_CTRL_WDT_EXT BIT(3)
	#define WDT_CTRL_WDT_INTR BIT(2)
	#define WDT_CTRL_RESET_SYSTEM BIT(1)
	#define WDT_CTRL_ENABLE BIT(0)
	#define WDT_TIMEOUT_STATUS 0x10
	#define WDT_TIMEOUT_STATUS_BOOT_SECONDARY BIT(1)
	#define WDT_CLEAR_TIMEOUT_STATUS 0x14
	#define WDT_CLEAR_TIMEOUT_AND_BOOT_CODE_SELECTION BIT(0)

	/*
	* WDT_RESET_WIDTH controls the characteristics of the external pulse (if
	* enabled), specifically:
	*
	* * Pulse duration
	* * Drive mode: push-pull vs open-drain
	* * Polarity: Active high or active low
	*
	* Pulse duration configuration is available on both the AST2400 and AST2500,
	* though the field changes between SoCs:
	*
	* AST2400: Bits 7:0
	* AST2500: Bits 19:0
	*
	* This difference is captured in struct aspeed_wdt_config.
	*
	* The AST2500 exposes the drive mode and polarity options, but not in a
	* regular fashion. For read purposes, bit 31 represents active high or low,
	* and bit 30 represents push-pull or open-drain. With respect to write, magic
	* values need to be written to the top byte to change the state of the drive
	* mode and polarity bits. Any other value written to the top byte has no
	* effect on the state of the drive mode or polarity bits. However, the pulse
	* width value must be preserved (as desired) if written.
	*/
	#define WDT_RESET_WIDTH 0x18
	#define WDT_RESET_WIDTH_ACTIVE_HIGH BIT(31)
	#define WDT_ACTIVE_HIGH_MAGIC (0xA5 << 24)
	#define WDT_ACTIVE_LOW_MAGIC (0x5A << 24)
	#define WDT_RESET_WIDTH_PUSH_PULL BIT(30)
	#define WDT_PUSH_PULL_MAGIC (0xA8 << 24)
	#define WDT_OPEN_DRAIN_MAGIC (0x8A << 24)

	#define WDT_RESTART_MAGIC 0x4755

	/* 32 bits at 1MHz, in milliseconds */
	#define WDT_MAX_TIMEOUT_MS 4294967
	#define WDT_DEFAULT_TIMEOUT 30
	#define WDT_RATE_1MHZ 1000000

	static struct aspeed_wdt to_aspeed_wdt(struct watchdog_device wdd)
	{
	return container_of(wdd, struct aspeed_wdt, wdd);
	}

	static void aspeed_wdt_enable(struct aspeed_wdt *wdt, int count)
	{
	wdt->ctrl \|= WDT_CTRL_ENABLE;

	writel(0, wdt->base + WDT_CTRL);
	writel(count, wdt->base + WDT_RELOAD_VALUE);
	writel(WDT_RESTART_MAGIC, wdt->base + WDT_RESTART);
	writel(wdt->ctrl, wdt->base + WDT_CTRL);
	}

	static int aspeed_wdt_start(struct watchdog_device *wdd)
	{
	struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);

	aspeed_wdt_enable(wdt, wdd->timeout * WDT_RATE_1MHZ);

	return 0;
	}

	static int aspeed_wdt_stop(struct watchdog_device *wdd)
	{
	struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);

	wdt->ctrl &= ~WDT_CTRL_ENABLE;
	writel(wdt->ctrl, wdt->base + WDT_CTRL);

	return 0;
	}

	static int aspeed_wdt_ping(struct watchdog_device *wdd)
	{
	struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);

	writel(WDT_RESTART_MAGIC, wdt->base + WDT_RESTART);

	return 0;
	}

	static int aspeed_wdt_set_timeout(struct watchdog_device *wdd,
	unsigned int timeout)
	{
	struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);
	u32 actual;

	wdd->timeout = timeout;

	actual = min(timeout, wdd->max_hw_heartbeat_ms / 1000);

	writel(actual * WDT_RATE_1MHZ, wdt->base + WDT_RELOAD_VALUE);
	writel(WDT_RESTART_MAGIC, wdt->base + WDT_RESTART);

	return 0;
	}

	static int aspeed_wdt_restart(struct watchdog_device *wdd,
	unsigned long action, void *data)
	{
	struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);

	wdt->ctrl &= ~WDT_CTRL_BOOT_SECONDARY;
	aspeed_wdt_enable(wdt, 128 * WDT_RATE_1MHZ / 1000);

	mdelay(1000);

	return 0;
	}

	/* access_cs0 shows if cs0 is accessible, hence the reverted bit */
	static ssize_t access_cs0_show(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct aspeed_wdt *wdt = dev_get_drvdata(dev);
	u32 status = readl(wdt->base + WDT_TIMEOUT_STATUS);

	return sysfs_emit(buf, "%u\n",
	!(status & WDT_TIMEOUT_STATUS_BOOT_SECONDARY));
	}

	static ssize_t access_cs0_store(struct device *dev,
	struct device_attribute attr, const char buf,
	size_t size)
	{
	struct aspeed_wdt *wdt = dev_get_drvdata(dev);
	unsigned long val;

	if (kstrtoul(buf, 10, &val))
	return -EINVAL;

	if (val)
	writel(WDT_CLEAR_TIMEOUT_AND_BOOT_CODE_SELECTION,
	wdt->base + WDT_CLEAR_TIMEOUT_STATUS);

	return size;
	}

	/*
	* This attribute exists only if the system has booted from the alternate
	* flash with 'alt-boot' option.
	*
	* At alternate flash the 'access_cs0' sysfs node provides:
	* ast2400: a way to get access to the primary SPI flash chip at CS0
	* after booting from the alternate chip at CS1.
	* ast2500: a way to restore the normal address mapping from
	* (CS0->CS1, CS1->CS0) to (CS0->CS0, CS1->CS1).
	*
	* Clearing the boot code selection and timeout counter also resets to the
	* initial state the chip select line mapping. When the SoC is in normal
	* mapping state (i.e. booted from CS0), clearing those bits does nothing for
	* both versions of the SoC. For alternate boot mode (booted from CS1 due to
	* wdt2 expiration) the behavior differs as described above.
	*
	* This option can be used with wdt2 (watchdog1) only.
	*/
	static DEVICE_ATTR_RW(access_cs0);

	static struct attribute *bswitch_attrs[] = {
	&dev_attr_access_cs0.attr,
	NULL
	};
	ATTRIBUTE_GROUPS(bswitch);

	static const struct watchdog_ops aspeed_wdt_ops = {
	.start = aspeed_wdt_start,
	.stop = aspeed_wdt_stop,
	.ping = aspeed_wdt_ping,
	.set_timeout = aspeed_wdt_set_timeout,
	.restart = aspeed_wdt_restart,
	.owner = THIS_MODULE,
	};

	static const struct watchdog_info aspeed_wdt_info = {
	.options = WDIOF_KEEPALIVEPING
	\| WDIOF_MAGICCLOSE
	\| WDIOF_SETTIMEOUT,
	.identity = KBUILD_MODNAME,
	};

	static int aspeed_wdt_probe(struct platform_device *pdev)
	{
	struct device *dev = &pdev->dev;
	const struct aspeed_wdt_config *config;
	const struct of_device_id *ofdid;
	struct aspeed_wdt *wdt;
	struct device_node *np;
	const char *reset_type;
	u32 duration;
	u32 status;
	int ret;

	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
	if (!wdt)
	return -ENOMEM;

	wdt->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(wdt->base))
	return PTR_ERR(wdt->base);

	wdt->wdd.info = &aspeed_wdt_info;
	wdt->wdd.ops = &aspeed_wdt_ops;
	wdt->wdd.max_hw_heartbeat_ms = WDT_MAX_TIMEOUT_MS;
	wdt->wdd.parent = dev;

	wdt->wdd.timeout = WDT_DEFAULT_TIMEOUT;
	watchdog_init_timeout(&wdt->wdd, 0, dev);

	watchdog_set_nowayout(&wdt->wdd, nowayout);

	np = dev->of_node;

	ofdid = of_match_node(aspeed_wdt_of_table, np);
	if (!ofdid)
	return -EINVAL;
	config = ofdid->data;

	/*
	* On clock rates:
	* - ast2400 wdt can run at PCLK, or 1MHz
	* - ast2500 only runs at 1MHz, hard coding bit 4 to 1
	* - ast2600 always runs at 1MHz
	*
	* Set the ast2400 to run at 1MHz as it simplifies the driver.
	*/
	if (of_device_is_compatible(np, "aspeed,ast2400-wdt"))
	wdt->ctrl = WDT_CTRL_1MHZ_CLK;

	/*
	* Control reset on a per-device basis to ensure the
	* host is not affected by a BMC reboot
	*/
	ret = of_property_read_string(np, "aspeed,reset-type", &reset_type);
	if (ret) {
	wdt->ctrl \|= WDT_CTRL_RESET_MODE_SOC \| WDT_CTRL_RESET_SYSTEM;
	} else {
	if (!strcmp(reset_type, "cpu"))
	wdt->ctrl \|= WDT_CTRL_RESET_MODE_ARM_CPU \|
	WDT_CTRL_RESET_SYSTEM;
	else if (!strcmp(reset_type, "soc"))
	wdt->ctrl \|= WDT_CTRL_RESET_MODE_SOC \|
	WDT_CTRL_RESET_SYSTEM;
	else if (!strcmp(reset_type, "system"))
	wdt->ctrl \|= WDT_CTRL_RESET_MODE_FULL_CHIP \|
	WDT_CTRL_RESET_SYSTEM;
	else if (strcmp(reset_type, "none"))
	return -EINVAL;
	}
	if (of_property_read_bool(np, "aspeed,external-signal"))
	wdt->ctrl \|= WDT_CTRL_WDT_EXT;
	if (of_property_read_bool(np, "aspeed,alt-boot"))
	wdt->ctrl \|= WDT_CTRL_BOOT_SECONDARY;

	if (readl(wdt->base + WDT_CTRL) & WDT_CTRL_ENABLE) {
	/*
	* The watchdog is running, but invoke aspeed_wdt_start() to
	* write wdt->ctrl to WDT_CTRL to ensure the watchdog's
	* configuration conforms to the driver's expectations.
	* Primarily, ensure we're using the 1MHz clock source.
	*/
	aspeed_wdt_start(&wdt->wdd);
	set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
	}

	if ((of_device_is_compatible(np, "aspeed,ast2500-wdt")) \|\|
	(of_device_is_compatible(np, "aspeed,ast2600-wdt"))) {
	u32 reg = readl(wdt->base + WDT_RESET_WIDTH);

	reg &= config->ext_pulse_width_mask;
	if (of_property_read_bool(np, "aspeed,ext-active-high"))
	reg \|= WDT_ACTIVE_HIGH_MAGIC;
	else
	reg \|= WDT_ACTIVE_LOW_MAGIC;

	writel(reg, wdt->base + WDT_RESET_WIDTH);

	reg &= config->ext_pulse_width_mask;
	if (of_property_read_bool(np, "aspeed,ext-push-pull"))
	reg \|= WDT_PUSH_PULL_MAGIC;
	else
	reg \|= WDT_OPEN_DRAIN_MAGIC;

	writel(reg, wdt->base + WDT_RESET_WIDTH);
	}

	if (!of_property_read_u32(np, "aspeed,ext-pulse-duration", &duration)) {
	u32 max_duration = config->ext_pulse_width_mask + 1;

	if (duration == 0 \|\| duration > max_duration) {
	dev_err(dev, "Invalid pulse duration: %uus\n",
	duration);
	duration = max(1U, min(max_duration, duration));
	dev_info(dev, "Pulse duration set to %uus\n",
	duration);
	}

	/*
	* The watchdog is always configured with a 1MHz source, so
	* there is no need to scale the microsecond value. However we
	* need to offset it - from the datasheet:
	*
	* "This register decides the asserting duration of wdt_ext and
	* wdt_rstarm signal. The default value is 0xFF. It means the
	* default asserting duration of wdt_ext and wdt_rstarm is
	* 256us."
	*
	* This implies a value of 0 gives a 1us pulse.
	*/
	writel(duration - 1, wdt->base + WDT_RESET_WIDTH);
	}

	status = readl(wdt->base + WDT_TIMEOUT_STATUS);
	if (status & WDT_TIMEOUT_STATUS_BOOT_SECONDARY) {
	wdt->wdd.bootstatus = WDIOF_CARDRESET;

	if (of_device_is_compatible(np, "aspeed,ast2400-wdt") \|\|
	of_device_is_compatible(np, "aspeed,ast2500-wdt"))
	wdt->wdd.groups = bswitch_groups;
	}

	dev_set_drvdata(dev, wdt);

	return devm_watchdog_register_device(dev, &wdt->wdd);
	}

	static struct platform_driver aspeed_watchdog_driver = {
	.probe = aspeed_wdt_probe,
	.driver = {
	.name = KBUILD_MODNAME,
	.of_match_table = of_match_ptr(aspeed_wdt_of_table),
	},
	};

	static int __init aspeed_wdt_init(void)
	{
	return platform_driver_register(&aspeed_watchdog_driver);
	}
	arch_initcall(aspeed_wdt_init);

	static void __exit aspeed_wdt_exit(void)
	{
	platform_driver_unregister(&aspeed_watchdog_driver);
	}
	module_exit(aspeed_wdt_exit);

	MODULE_DESCRIPTION("Aspeed Watchdog Driver");
	MODULE_LICENSE("GPL");