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>

1 files changed, 268 insertions, 0 deletions

diff --git a/drivers/watchdog/bcm_kona_wdt.c b/drivers/watchdog/bcm_kona_wdt.c
new file mode 100644
index 000000000000..7e41a83eb45e
--- /dev/null
+++ b/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");