watchdog: Add Toshiba Visconti watchdog driver

Add the watchdog driver for Toshiba Visconti series.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Reviewed-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20201005023012.603026-3-nobuhiro1.iwamatsu@toshiba.co.jp
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/Kconfig

@@ -1004,6 +1004,14 @@ config PM8916_WATCHDOG
 	  Say Y here to include support watchdog timer embedded into the
 	  pm8916 module.
 
+config VISCONTI_WATCHDOG
+	tristate "Toshiba Visconti series watchdog support"
+	depends on ARCH_VISCONTI || COMPILE_TEST
+	select WATCHDOG_CORE
+	help
+	  Say Y here to include support for the watchdog timer in Toshiba
+	  Visconti SoCs.
+
 # X86 (i386 + ia64 + x86_64) Architecture
 
 config ACQUIRE_WDT

drivers/watchdog/Makefile

@@ -95,6 +95,7 @@ obj-$(CONFIG_RTD119X_WATCHDOG) += rtd119x_wdt.o
 obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
 obj-$(CONFIG_PM8916_WATCHDOG) += pm8916_wdt.o
 obj-$(CONFIG_ARM_SMC_WATCHDOG) += arm_smc_wdt.o
+obj-$(CONFIG_VISCONTI_WATCHDOG) += visconti_wdt.o
 
 # X86 (i386 + ia64 + x86_64) Architecture
 obj-$(CONFIG_ACQUIRE_WDT) += acquirewdt.o

drivers/watchdog/visconti_wdt.c

@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2020 TOSHIBA CORPORATION
+ * Copyright (c) 2020 Toshiba Electronic Devices & Storage Corporation
+ * Copyright (c) 2020 Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
+ */
+
+#include <linux/clk.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>
+
+#define WDT_CNT			0x00
+#define WDT_MIN			0x04
+#define WDT_MAX			0x08
+#define WDT_CTL			0x0c
+#define WDT_CMD			0x10
+#define WDT_CMD_CLEAR		0x4352
+#define WDT_CMD_START_STOP	0x5354
+#define WDT_DIV			0x30
+
+#define VISCONTI_WDT_FREQ	2000000 /* 2MHz */
+#define WDT_DEFAULT_TIMEOUT	10U /* in seconds */
+
+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 visconti_wdt_priv {
+	struct watchdog_device wdev;
+	void __iomem *base;
+	u32 div;
+};
+
+static int visconti_wdt_start(struct watchdog_device *wdev)
+{
+	struct visconti_wdt_priv *priv = watchdog_get_drvdata(wdev);
+	u32 timeout = wdev->timeout * VISCONTI_WDT_FREQ;
+
+	writel(priv->div, priv->base + WDT_DIV);
+	writel(0, priv->base + WDT_MIN);
+	writel(timeout, priv->base + WDT_MAX);
+	writel(0, priv->base + WDT_CTL);
+	writel(WDT_CMD_START_STOP, priv->base + WDT_CMD);
+
+	return 0;
+}
+
+static int visconti_wdt_stop(struct watchdog_device *wdev)
+{
+	struct visconti_wdt_priv *priv = watchdog_get_drvdata(wdev);
+
+	writel(1, priv->base + WDT_CTL);
+	writel(WDT_CMD_START_STOP, priv->base + WDT_CMD);
+
+	return 0;
+}
+
+static int visconti_wdt_ping(struct watchdog_device *wdd)
+{
+	struct visconti_wdt_priv *priv = watchdog_get_drvdata(wdd);
+
+	writel(WDT_CMD_CLEAR, priv->base + WDT_CMD);
+
+	return 0;
+}
+
+static unsigned int visconti_wdt_get_timeleft(struct watchdog_device *wdev)
+{
+	struct visconti_wdt_priv *priv = watchdog_get_drvdata(wdev);
+	u32 timeout = wdev->timeout * VISCONTI_WDT_FREQ;
+	u32 cnt = readl(priv->base + WDT_CNT);
+
+	if (timeout <= cnt)
+		return 0;
+	timeout -= cnt;
+
+	return timeout / VISCONTI_WDT_FREQ;
+}
+
+static int visconti_wdt_set_timeout(struct watchdog_device *wdev, unsigned int timeout)
+{
+	u32 val;
+	struct visconti_wdt_priv *priv = watchdog_get_drvdata(wdev);
+
+	wdev->timeout = timeout;
+	val = wdev->timeout * VISCONTI_WDT_FREQ;
+
+	/* Clear counter before setting timeout because WDT expires */
+	writel(WDT_CMD_CLEAR, priv->base + WDT_CMD);
+	writel(val, priv->base + WDT_MAX);
+
+	return 0;
+}
+
+static const struct watchdog_info visconti_wdt_info = {
+	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
+	.identity = "Visconti Watchdog",
+};
+
+static const struct watchdog_ops visconti_wdt_ops = {
+	.owner		= THIS_MODULE,
+	.start		= visconti_wdt_start,
+	.stop		= visconti_wdt_stop,
+	.ping		= visconti_wdt_ping,
+	.get_timeleft	= visconti_wdt_get_timeleft,
+	.set_timeout	= visconti_wdt_set_timeout,
+};
+
+static void visconti_clk_disable_unprepare(void *data)
+{
+	clk_disable_unprepare(data);
+}
+
+static int visconti_wdt_probe(struct platform_device *pdev)
+{
+	struct watchdog_device *wdev;
+	struct visconti_wdt_priv *priv;
+	struct device *dev = &pdev->dev;
+	struct clk *clk;
+	int ret;
+	unsigned long clk_freq;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk), "Could not get clock\n");
+
+	ret = clk_prepare_enable(clk);
+	if (ret) {
+		dev_err(dev, "Could not enable clock\n");
+		return ret;
+	}
+
+	ret = devm_add_action_or_reset(dev, visconti_clk_disable_unprepare, clk);
+	if (ret)
+		return ret;
+
+	clk_freq = clk_get_rate(clk);
+	if (!clk_freq)
+		return -EINVAL;
+
+	priv->div = clk_freq / VISCONTI_WDT_FREQ;
+
+	/* Initialize struct watchdog_device. */
+	wdev = &priv->wdev;
+	wdev->info = &visconti_wdt_info;
+	wdev->ops = &visconti_wdt_ops;
+	wdev->parent = dev;
+	wdev->min_timeout = 1;
+	wdev->max_timeout = 0xffffffff / VISCONTI_WDT_FREQ;
+	wdev->timeout = min(wdev->max_timeout, WDT_DEFAULT_TIMEOUT);
+
+	watchdog_set_drvdata(wdev, priv);
+	watchdog_set_nowayout(wdev, nowayout);
+	watchdog_stop_on_unregister(wdev);
+
+	/* This overrides the default timeout only if DT configuration was found */
+	ret = watchdog_init_timeout(wdev, 0, dev);
+	if (ret)
+		dev_warn(dev, "Specified timeout value invalid, using default\n");
+
+	return devm_watchdog_register_device(dev, wdev);
+}
+
+static const struct of_device_id visconti_wdt_of_match[] = {
+	{ .compatible = "toshiba,visconti-wdt", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, visconti_wdt_of_match);
+
+static struct platform_driver visconti_wdt_driver = {
+	.driver = {
+			.name = "visconti_wdt",
+			.of_match_table = visconti_wdt_of_match,
+		},
+	.probe = visconti_wdt_probe,
+};
+module_platform_driver(visconti_wdt_driver);
+
+MODULE_DESCRIPTION("TOSHIBA Visconti Watchdog Driver");
+MODULE_AUTHOR("Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp");
+MODULE_LICENSE("GPL v2");