watchdog: digicolor: driver for Conexant Digicolor CX92755 SoC

This commit add a driver for the watchdog functionality of the Conexant CX92755
SoC, from the Digicolor series of SoCs. Of 8 system timers provided by the
CX92755, the first one, timer A, can reset the chip when its counter reaches
zero. This driver uses this capability to provide userspace with a standard
watchdog, using the watchdog timer driver core framework. This driver also
implements a reboot handler for the reboot(2) system call.

The watchdog driver shares the timer registers with the CX92755 timer driver
(drivers/clocksource/timer-digicolor.c). The timer driver, however, uses only
timers other than A, so both drivers should coexist.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

3 files changed, 216 insertions, 0 deletions

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 262647bbc614..c572a86c6a4e 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -526,6 +526,16 @@ config MEDIATEK_WATCHDOG
           To compile this driver as a module, choose M here: the
           module will be called mtk_wdt.
 
+config DIGICOLOR_WATCHDOG
+        tristate "Conexant Digicolor SoCs watchdog support"
+        depends on ARCH_DIGICOLOR
+        select WATCHDOG_CORE
+        help
+          Say Y here to include support for the watchdog timer
+          in Conexant Digicolor SoCs.
+          To compile this driver as a module, choose M here: the
+          module will be called digicolor_wdt.
+
 # AVR32 Architecture
 
 config AT32AP700X_WDT
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index d98768c7d928..4e26613a7f52 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -65,6 +65,7 @@ obj-$(CONFIG_BCM_KONA_WDT) += bcm_kona_wdt.o
 obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
 obj-$(CONFIG_MESON_WATCHDOG) += meson_wdt.o
 obj-$(CONFIG_MEDIATEK_WATCHDOG) += mtk_wdt.o
+obj-$(CONFIG_DIGICOLOR_WATCHDOG) += digicolor_wdt.o
 
 # AVR32 Architecture
 obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o
diff --git a/drivers/watchdog/digicolor_wdt.c b/drivers/watchdog/digicolor_wdt.c
new file mode 100644
index 000000000000..31d8e4936611
--- /dev/null
+++ b/drivers/watchdog/digicolor_wdt.c
@@ -0,0 +1,205 @@
+/*
+ * Watchdog driver for Conexant Digicolor
+ *
+ * Copyright (C) 2015 Paradox Innovation Ltd.
+ *
+ * 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; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/delay.h>
+#include <linux/clk.h>
+#include <linux/watchdog.h>
+#include <linux/reboot.h>
+#include <linux/platform_device.h>
+#include <linux/of_address.h>
+
+#define TIMER_A_CONTROL         0
+#define TIMER_A_COUNT           4
+
+#define TIMER_A_ENABLE_COUNT    BIT(0)
+#define TIMER_A_ENABLE_WATCHDOG BIT(1)
+
+struct dc_wdt {
+        void __iomem            *base;
+        struct clk              *clk;
+        struct notifier_block   restart_handler;
+        spinlock_t              lock;
+};
+
+static unsigned timeout;
+module_param(timeout, uint, 0);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds");
+
+static void dc_wdt_set(struct dc_wdt *wdt, u32 ticks)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&wdt->lock, flags);
+
+        writel_relaxed(0, wdt->base + TIMER_A_CONTROL);
+        writel_relaxed(ticks, wdt->base + TIMER_A_COUNT);
+        writel_relaxed(TIMER_A_ENABLE_COUNT | TIMER_A_ENABLE_WATCHDOG,
+                       wdt->base + TIMER_A_CONTROL);
+
+        spin_unlock_irqrestore(&wdt->lock, flags);
+}
+
+static int dc_restart_handler(struct notifier_block *this, unsigned long mode,
+                              void *cmd)
+{
+        struct dc_wdt *wdt = container_of(this, struct dc_wdt, restart_handler);
+
+        dc_wdt_set(wdt, 1);
+        /* wait for reset to assert... */
+        mdelay(500);
+
+        return NOTIFY_DONE;
+}
+
+static int dc_wdt_start(struct watchdog_device *wdog)
+{
+        struct dc_wdt *wdt = watchdog_get_drvdata(wdog);
+
+        dc_wdt_set(wdt, wdog->timeout * clk_get_rate(wdt->clk));
+
+        return 0;
+}
+
+static int dc_wdt_stop(struct watchdog_device *wdog)
+{
+        struct dc_wdt *wdt = watchdog_get_drvdata(wdog);
+
+        writel_relaxed(0, wdt->base + TIMER_A_CONTROL);
+
+        return 0;
+}
+
+static int dc_wdt_set_timeout(struct watchdog_device *wdog, unsigned int t)
+{
+        struct dc_wdt *wdt = watchdog_get_drvdata(wdog);
+
+        dc_wdt_set(wdt, t * clk_get_rate(wdt->clk));
+        wdog->timeout = t;
+
+        return 0;
+}
+
+static unsigned int dc_wdt_get_timeleft(struct watchdog_device *wdog)
+{
+        struct dc_wdt *wdt = watchdog_get_drvdata(wdog);
+        uint32_t count = readl_relaxed(wdt->base + TIMER_A_COUNT);
+
+        return count / clk_get_rate(wdt->clk);
+}
+
+static struct watchdog_ops dc_wdt_ops = {
+        .owner          = THIS_MODULE,
+        .start          = dc_wdt_start,
+        .stop           = dc_wdt_stop,
+        .set_timeout    = dc_wdt_set_timeout,
+        .get_timeleft   = dc_wdt_get_timeleft,
+};
+
+static struct watchdog_info dc_wdt_info = {
+        .options        = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE
+                        | WDIOF_KEEPALIVEPING,
+        .identity       = "Conexant Digicolor Watchdog",
+};
+
+static struct watchdog_device dc_wdt_wdd = {
+        .info           = &dc_wdt_info,
+        .ops            = &dc_wdt_ops,
+        .min_timeout    = 1,
+};
+
+static int dc_wdt_probe(struct platform_device *pdev)
+{
+        struct device *dev = &pdev->dev;
+        struct device_node *np = dev->of_node;
+        struct dc_wdt *wdt;
+        int ret;
+
+        wdt = devm_kzalloc(dev, sizeof(struct dc_wdt), GFP_KERNEL);
+        if (!wdt)
+                return -ENOMEM;
+        platform_set_drvdata(pdev, wdt);
+
+        wdt->base = of_iomap(np, 0);
+        if (!wdt->base) {
+                dev_err(dev, "Failed to remap watchdog regs");
+                return -ENODEV;
+        }
+
+        wdt->clk = devm_clk_get(&pdev->dev, NULL);
+        if (IS_ERR(wdt->clk)) {
+                ret = PTR_ERR(wdt->clk);
+                goto err_iounmap;
+        }
+        dc_wdt_wdd.max_timeout = U32_MAX / clk_get_rate(wdt->clk);
+        dc_wdt_wdd.timeout = dc_wdt_wdd.max_timeout;
+
+        spin_lock_init(&wdt->lock);
+
+        watchdog_set_drvdata(&dc_wdt_wdd, wdt);
+        watchdog_init_timeout(&dc_wdt_wdd, timeout, dev);
+        ret = watchdog_register_device(&dc_wdt_wdd);
+        if (ret) {
+                dev_err(dev, "Failed to register watchdog device");
+                goto err_iounmap;
+        }
+
+        wdt->restart_handler.notifier_call = dc_restart_handler;
+        wdt->restart_handler.priority = 128;
+        ret = register_restart_handler(&wdt->restart_handler);
+        if (ret)
+                dev_warn(&pdev->dev, "cannot register restart handler\n");
+
+        return 0;
+
+err_iounmap:
+        iounmap(wdt->base);
+        return ret;
+}
+
+static int dc_wdt_remove(struct platform_device *pdev)
+{
+        struct dc_wdt *wdt = platform_get_drvdata(pdev);
+
+        unregister_restart_handler(&wdt->restart_handler);
+        watchdog_unregister_device(&dc_wdt_wdd);
+        iounmap(wdt->base);
+
+        return 0;
+}
+
+static void dc_wdt_shutdown(struct platform_device *pdev)
+{
+        dc_wdt_stop(&dc_wdt_wdd);
+}
+
+static const struct of_device_id dc_wdt_of_match[] = {
+        { .compatible = "cnxt,cx92755-wdt", },
+        {},
+};
+MODULE_DEVICE_TABLE(of, dc_wdt_of_match);
+
+static struct platform_driver dc_wdt_driver = {
+        .probe          = dc_wdt_probe,
+        .remove         = dc_wdt_remove,
+        .shutdown       = dc_wdt_shutdown,
+        .driver = {
+                .name =         "digicolor-wdt",
+                .of_match_table = dc_wdt_of_match,
+        },
+};
+module_platform_driver(dc_wdt_driver);
+
+MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
+MODULE_DESCRIPTION("Driver for Conexant Digicolor watchdog timer");
+MODULE_LICENSE("GPL");