watchdog: bcm281xx: Watchdog Driver

This commit adds support for the watchdog timer used on the BCM281xx
family of SoCs.

Signed-off-by: Markus Mayer <markus.mayer@linaro.org>
Reviewed-by: Matt Porter <matt.porter@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

arch/arm/configs/bcm_defconfig

@@ -126,3 +126,5 @@ CONFIG_CRC7=y
 CONFIG_XZ_DEC=y
 CONFIG_AVERAGE=y
 CONFIG_PINCTRL_CAPRI=y
+CONFIG_WATCHDOG=y
+CONFIG_BCM_KONA_WDT=y

drivers/watchdog/Kconfig

@@ -1139,6 +1139,18 @@ config BCM2835_WDT
 	  To compile this driver as a loadable module, choose M here.
 	  The module will be called bcm2835_wdt.
 
+config BCM_KONA_WDT
+	tristate "BCM Kona Watchdog"
+	depends on ARCH_BCM
+	select WATCHDOG_CORE
+	help
+	  Support for the watchdog timer on the following Broadcom BCM281xx
+	  family, which includes BCM11130, BCM11140, BCM11351, BCM28145 and
+	  BCM28155 variants.
+
+	  Say 'Y' or 'M' here to enable the driver. The module will be called
+	  bcm_kona_wdt.
+
 config LANTIQ_WDT
 	tristate "Lantiq SoC watchdog"
 	depends on LANTIQ

drivers/watchdog/Makefile

@@ -57,6 +57,7 @@ obj-$(CONFIG_RETU_WATCHDOG) += retu_wdt.o
 obj-$(CONFIG_BCM2835_WDT) += bcm2835_wdt.o
 obj-$(CONFIG_MOXART_WDT) += moxart_wdt.o
 obj-$(CONFIG_SIRFSOC_WATCHDOG) += sirfsoc_wdt.o
+obj-$(CONFIG_BCM_KONA_WDT) += bcm_kona_wdt.o
 
 # AVR32 Architecture
 obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o

drivers/watchdog/bcm_kona_wdt.c

@@ -0,0 +1,268 @@
+/*
+ * Copyright (C) 2013 Broadcom Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation version 2.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+#define SECWDOG_CTRL_REG		0x00000000
+#define SECWDOG_COUNT_REG		0x00000004
+
+#define SECWDOG_RESERVED_MASK		0x1dffffff
+#define SECWDOG_WD_LOAD_FLAG		0x10000000
+#define SECWDOG_EN_MASK			0x08000000
+#define SECWDOG_SRSTEN_MASK		0x04000000
+#define SECWDOG_RES_MASK		0x00f00000
+#define SECWDOG_COUNT_MASK		0x000fffff
+
+#define SECWDOG_MAX_COUNT		SECWDOG_COUNT_MASK
+#define SECWDOG_CLKS_SHIFT		20
+#define SECWDOG_MAX_RES			15
+#define SECWDOG_DEFAULT_RESOLUTION	4
+#define SECWDOG_MAX_TRY			1000
+
+#define SECS_TO_TICKS(x, w)		((x) << (w)->resolution)
+#define TICKS_TO_SECS(x, w)		((x) >> (w)->resolution)
+
+#define BCM_KONA_WDT_NAME		"bcm_kona_wdt"
+
+struct bcm_kona_wdt {
+	void __iomem *base;
+	/*
+	 * One watchdog tick is 1/(2^resolution) seconds. Resolution can take
+	 * the values 0-15, meaning one tick can be 1s to 30.52us. Our default
+	 * resolution of 4 means one tick is 62.5ms.
+	 *
+	 * The watchdog counter is 20 bits. Depending on resolution, the maximum
+	 * counter value of 0xfffff expires after about 12 days (resolution 0)
+	 * down to only 32s (resolution 15). The default resolution of 4 gives
+	 * us a maximum of about 18 hours and 12 minutes before the watchdog
+	 * times out.
+	 */
+	int resolution;
+	spinlock_t lock;
+};
+
+static int secure_register_read(void __iomem *addr)
+{
+	uint32_t val;
+	unsigned count = 0;
+
+	/*
+	 * If the WD_LOAD_FLAG is set, the watchdog counter field is being
+	 * updated in hardware. Once the WD timer is updated in hardware, it
+	 * gets cleared.
+	 */
+	do {
+		if (unlikely(count > 1))
+			udelay(5);
+		val = readl_relaxed(addr);
+		count++;
+	} while ((val & SECWDOG_WD_LOAD_FLAG) && count < SECWDOG_MAX_TRY);
+
+	/* This is the only place we return a negative value. */
+	if (val & SECWDOG_WD_LOAD_FLAG)
+		return -ETIMEDOUT;
+
+	/* We always mask out reserved bits. */
+	val &= SECWDOG_RESERVED_MASK;
+
+	return val;
+}
+
+static int bcm_kona_wdt_ctrl_reg_modify(struct bcm_kona_wdt *wdt,
+					unsigned mask, unsigned newval)
+{
+	int val;
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&wdt->lock, flags);
+
+	val = secure_register_read(wdt->base + SECWDOG_CTRL_REG);
+	if (val < 0) {
+		ret = val;
+	} else {
+		val &= ~mask;
+		val |= newval;
+		writel_relaxed(val, wdt->base + SECWDOG_CTRL_REG);
+	}
+
+	spin_unlock_irqrestore(&wdt->lock, flags);
+
+	return ret;
+}
+
+static int bcm_kona_wdt_set_resolution_reg(struct bcm_kona_wdt *wdt)
+{
+	if (wdt->resolution > SECWDOG_MAX_RES)
+		return -EINVAL;
+
+	return bcm_kona_wdt_ctrl_reg_modify(wdt, SECWDOG_RES_MASK,
+					wdt->resolution << SECWDOG_CLKS_SHIFT);
+}
+
+static int bcm_kona_wdt_set_timeout_reg(struct watchdog_device *wdog,
+					unsigned watchdog_flags)
+{
+	struct bcm_kona_wdt *wdt = watchdog_get_drvdata(wdog);
+
+	return bcm_kona_wdt_ctrl_reg_modify(wdt, SECWDOG_COUNT_MASK,
+					SECS_TO_TICKS(wdog->timeout, wdt) |
+					watchdog_flags);
+}
+
+static int bcm_kona_wdt_set_timeout(struct watchdog_device *wdog,
+	unsigned int t)
+{
+	wdog->timeout = t;
+	return 0;
+}
+
+static unsigned int bcm_kona_wdt_get_timeleft(struct watchdog_device *wdog)
+{
+	struct bcm_kona_wdt *wdt = watchdog_get_drvdata(wdog);
+	int val;
+	unsigned long flags;
+
+	spin_lock_irqsave(&wdt->lock, flags);
+	val = secure_register_read(wdt->base + SECWDOG_COUNT_REG);
+	spin_unlock_irqrestore(&wdt->lock, flags);
+
+	if (val < 0)
+		return val;
+
+	return TICKS_TO_SECS(val & SECWDOG_COUNT_MASK, wdt);
+}
+
+static int bcm_kona_wdt_start(struct watchdog_device *wdog)
+{
+	return bcm_kona_wdt_set_timeout_reg(wdog,
+					SECWDOG_EN_MASK | SECWDOG_SRSTEN_MASK);
+}
+
+static int bcm_kona_wdt_stop(struct watchdog_device *wdog)
+{
+	struct bcm_kona_wdt *wdt = watchdog_get_drvdata(wdog);
+
+	return bcm_kona_wdt_ctrl_reg_modify(wdt, SECWDOG_EN_MASK |
+					    SECWDOG_SRSTEN_MASK, 0);
+}
+
+static struct watchdog_ops bcm_kona_wdt_ops = {
+	.owner =	THIS_MODULE,
+	.start =	bcm_kona_wdt_start,
+	.stop =		bcm_kona_wdt_stop,
+	.set_timeout =	bcm_kona_wdt_set_timeout,
+	.get_timeleft =	bcm_kona_wdt_get_timeleft,
+};
+
+static struct watchdog_info bcm_kona_wdt_info = {
+	.options =	WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
+			WDIOF_KEEPALIVEPING,
+	.identity =	"Broadcom Kona Watchdog Timer",
+};
+
+static struct watchdog_device bcm_kona_wdt_wdd = {
+	.info =		&bcm_kona_wdt_info,
+	.ops =		&bcm_kona_wdt_ops,
+	.min_timeout =	1,
+	.max_timeout =	SECWDOG_MAX_COUNT >> SECWDOG_DEFAULT_RESOLUTION,
+	.timeout =	SECWDOG_MAX_COUNT >> SECWDOG_DEFAULT_RESOLUTION,
+};
+
+static void bcm_kona_wdt_shutdown(struct platform_device *pdev)
+{
+	bcm_kona_wdt_stop(&bcm_kona_wdt_wdd);
+}
+
+static int bcm_kona_wdt_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct bcm_kona_wdt *wdt;
+	struct resource *res;
+	int ret;
+
+	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
+	if (!wdt)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	wdt->base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(wdt->base))
+		return -ENODEV;
+
+	wdt->resolution = SECWDOG_DEFAULT_RESOLUTION;
+	ret = bcm_kona_wdt_set_resolution_reg(wdt);
+	if (ret) {
+		dev_err(dev, "Failed to set resolution (error: %d)", ret);
+		return ret;
+	}
+
+	spin_lock_init(&wdt->lock);
+	platform_set_drvdata(pdev, wdt);
+	watchdog_set_drvdata(&bcm_kona_wdt_wdd, wdt);
+
+	ret = bcm_kona_wdt_set_timeout_reg(&bcm_kona_wdt_wdd, 0);
+	if (ret) {
+		dev_err(dev, "Failed set watchdog timeout");
+		return ret;
+	}
+
+	ret = watchdog_register_device(&bcm_kona_wdt_wdd);
+	if (ret) {
+		dev_err(dev, "Failed to register watchdog device");
+		return ret;
+	}
+
+	dev_dbg(dev, "Broadcom Kona Watchdog Timer");
+
+	return 0;
+}
+
+static int bcm_kona_wdt_remove(struct platform_device *pdev)
+{
+	bcm_kona_wdt_shutdown(pdev);
+	watchdog_unregister_device(&bcm_kona_wdt_wdd);
+	dev_dbg(&pdev->dev, "Watchdog driver disabled");
+
+	return 0;
+}
+
+static const struct of_device_id bcm_kona_wdt_of_match[] = {
+	{ .compatible = "brcm,kona-wdt", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, bcm_kona_wdt_of_match);
+
+static struct platform_driver bcm_kona_wdt_driver = {
+	.driver = {
+			.name = BCM_KONA_WDT_NAME,
+			.owner = THIS_MODULE,
+			.of_match_table = bcm_kona_wdt_of_match,
+		  },
+	.probe = bcm_kona_wdt_probe,
+	.remove = bcm_kona_wdt_remove,
+	.shutdown = bcm_kona_wdt_shutdown,
+};
+
+module_platform_driver(bcm_kona_wdt_driver);
+
+MODULE_ALIAS("platform:" BCM_KONA_WDT_NAME);
+MODULE_AUTHOR("Markus Mayer <mmayer@broadcom.com>");
+MODULE_DESCRIPTION("Broadcom Kona Watchdog Driver");
+MODULE_LICENSE("GPL v2");