[PATCH v7 2/2] watchdog: Add watchdog driver for Sunplus SP7021

[Xiantao Hu]

Sunplus SP7021 requires watchdog timer support.
Add watchdog driver to enable this.

Signed-off-by: Xiantao Hu <xt.hu@xxxxxxxxxxx>
---
Changes in v7:
 - Addressed all comments from Mr. Guenter Roeck.
   Fix sp_wdt_ping() and add comment to explain the calculation.

 MAINTAINERS                    |   1 +
 drivers/watchdog/Kconfig       |  11 ++
 drivers/watchdog/Makefile      |   1 +
 drivers/watchdog/sunplus_wdt.c | 220 +++++++++++++++++++++++++++++++++
 4 files changed, 233 insertions(+)
 create mode 100644 drivers/watchdog/sunplus_wdt.c

diff --git a/MAINTAINERS b/MAINTAINERS
index fe6cc971c..a1b3d76e2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18247,6 +18247,7 @@ M:	Xiantao Hu <xt.hu@xxxxxxxxxxx>
 L:	linux-watchdog@xxxxxxxxxxxxxxx
 S:	Maintained
 F:	Documentation/devicetree/bindings/watchdog/sunplus,sp7021-wdt.yaml
+F:	drivers/watchdog/sunplus_wdt.c
 
 SUPERH
 M:	Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 9d222ba17..d3dbe8695 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -976,6 +976,17 @@ config MSC313E_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called msc313e_wdt.
 
+config SUNPLUS_WATCHDOG
+	tristate "Sunplus watchdog support"
+	depends on ARCH_SUNPLUS || COMPILE_TEST
+	select WATCHDOG_CORE
+	help
+	  Say Y here to include support for the watchdog timer
+	  in Sunplus SoCs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called sunplus_wdt.
+
 # X86 (i386 + ia64 + x86_64) Architecture
 
 config ACQUIRE_WDT
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 2ee970641..0fa548ee6 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -93,6 +93,7 @@ obj-$(CONFIG_PM8916_WATCHDOG) += pm8916_wdt.o
 obj-$(CONFIG_ARM_SMC_WATCHDOG) += arm_smc_wdt.o
 obj-$(CONFIG_VISCONTI_WATCHDOG) += visconti_wdt.o
 obj-$(CONFIG_MSC313E_WATCHDOG) += msc313e_wdt.o
+obj-$(CONFIG_SUNPLUS_WATCHDOG) += sunplus_wdt.o
 
 # X86 (i386 + ia64 + x86_64) Architecture
 obj-$(CONFIG_ACQUIRE_WDT) += acquirewdt.o
diff --git a/drivers/watchdog/sunplus_wdt.c b/drivers/watchdog/sunplus_wdt.c
new file mode 100644
index 000000000..e2d8c532b
--- /dev/null
+++ b/drivers/watchdog/sunplus_wdt.c
@@ -0,0 +1,220 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * sunplus Watchdog Driver
+ *
+ * Copyright (C) 2021 Sunplus Technology Co., Ltd.
+ *
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/reset.h>
+#include <linux/watchdog.h>
+
+#define WDT_CTRL		0x00
+#define WDT_CNT			0x04
+
+#define WDT_STOP		0x3877
+#define WDT_RESUME		0x4A4B
+#define WDT_CLRIRQ		0x7482
+#define WDT_UNLOCK		0xAB00
+#define WDT_LOCK		0xAB01
+#define WDT_CONMAX		0xDEAF
+
+/* TIMEOUT_MAX = ffff0/90kHz =11.65, so longer than 11 seconds will time out. */
+#define SP_WDT_MAX_TIMEOUT	11U
+#define SP_WDT_DEFAULT_TIMEOUT	10
+
+#define STC_CLK			90000
+
+#define DEVICE_NAME		"sunplus-wdt"
+
+static unsigned int timeout;
+module_param(timeout, int, 0);
+MODULE_PARM_DESC(timeout, "Watchdog timeout 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 sp_wdt_priv {
+	struct watchdog_device wdev;
+	void __iomem *base;
+	struct clk *clk;
+	struct reset_control *rstc;
+};
+
+static int sp_wdt_restart(struct watchdog_device *wdev,
+			  unsigned long action, void *data)
+{
+	struct sp_wdt_priv *priv = watchdog_get_drvdata(wdev);
+	void __iomem *base = priv->base;
+
+	writel(WDT_STOP, base + WDT_CTRL);
+	writel(WDT_UNLOCK, base + WDT_CTRL);
+	writel(0x0001, base + WDT_CNT);
+	writel(WDT_LOCK, base + WDT_CTRL);
+	writel(WDT_RESUME, base + WDT_CTRL);
+
+	return 0;
+}
+
+static int sp_wdt_ping(struct watchdog_device *wdev)
+{
+	struct sp_wdt_priv *priv = watchdog_get_drvdata(wdev);
+	void __iomem *base = priv->base;
+	u32 count;
+
+	if (wdev->timeout > SP_WDT_MAX_TIMEOUT) {
+		/* WDT_CONMAX sets the count to the maximum (down-counting). */
+		writel(WDT_CONMAX, base + WDT_CTRL);
+	} else {
+		writel(WDT_UNLOCK, base + WDT_CTRL);
+		/*
+		 * Watchdog timer is a 20-bit down-counting based on STC_CLK.
+		 * This register bits[16:0] is from bit[19:4] of the watchdog
+		 * timer counter.
+		 */
+		count = (wdev->timeout * STC_CLK) >> 4;
+		writel(count, base + WDT_CNT);
+		writel(WDT_LOCK, base + WDT_CTRL);
+	}
+
+	return 0;
+}
+
+static int sp_wdt_stop(struct watchdog_device *wdev)
+{
+	struct sp_wdt_priv *priv = watchdog_get_drvdata(wdev);
+	void __iomem *base = priv->base;
+
+	writel(WDT_STOP, base + WDT_CTRL);
+
+	return 0;
+}
+
+static int sp_wdt_start(struct watchdog_device *wdev)
+{
+	struct sp_wdt_priv *priv = watchdog_get_drvdata(wdev);
+	void __iomem *base = priv->base;
+
+	writel(WDT_RESUME, base + WDT_CTRL);
+
+	return 0;
+}
+
+static unsigned int sp_wdt_get_timeleft(struct watchdog_device *wdev)
+{
+	struct sp_wdt_priv *priv = watchdog_get_drvdata(wdev);
+	void __iomem *base = priv->base;
+	u32 val;
+
+	val = readl(base + WDT_CNT);
+	val &= 0xffff;
+	val = val << 4;
+
+	return val;
+}
+
+static const struct watchdog_info sp_wdt_info = {
+	.identity	= DEVICE_NAME,
+	.options	= WDIOF_SETTIMEOUT |
+			  WDIOF_MAGICCLOSE |
+			  WDIOF_KEEPALIVEPING,
+};
+
+static const struct watchdog_ops sp_wdt_ops = {
+	.owner		= THIS_MODULE,
+	.start		= sp_wdt_start,
+	.stop		= sp_wdt_stop,
+	.ping		= sp_wdt_ping,
+	.get_timeleft	= sp_wdt_get_timeleft,
+	.restart	= sp_wdt_restart,
+};
+
+static void sp_clk_disable_unprepare(void *data)
+{
+	clk_disable_unprepare(data);
+}
+
+static void sp_reset_control_assert(void *data)
+{
+	reset_control_assert(data);
+}
+
+static int sp_wdt_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct sp_wdt_priv *priv;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(priv->clk))
+		return dev_err_probe(dev, PTR_ERR(priv->clk), "Failed to get clock\n");
+
+	ret = clk_prepare_enable(priv->clk);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to enable clock\n");
+
+	ret = devm_add_action_or_reset(dev, sp_clk_disable_unprepare, priv->clk);
+	if (ret)
+		return ret;
+
+	/* The timer and watchdog shared the STC reset */
+	priv->rstc = devm_reset_control_get_shared(dev, NULL);
+	if (IS_ERR(priv->rstc))
+		return dev_err_probe(dev, PTR_ERR(priv->rstc), "Failed to get reset\n");
+
+	reset_control_deassert(priv->rstc);
+
+	ret = devm_add_action_or_reset(dev, sp_reset_control_assert, priv->rstc);
+	if (ret)
+		return ret;
+
+	priv->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	priv->wdev.info = &sp_wdt_info;
+	priv->wdev.ops = &sp_wdt_ops;
+	priv->wdev.timeout = SP_WDT_DEFAULT_TIMEOUT;
+	priv->wdev.max_hw_heartbeat_ms = SP_WDT_MAX_TIMEOUT * 1000;
+	priv->wdev.min_timeout = 1;
+	priv->wdev.parent = dev;
+
+	watchdog_set_drvdata(&priv->wdev, priv);
+	watchdog_init_timeout(&priv->wdev, timeout, dev);
+	watchdog_set_nowayout(&priv->wdev, nowayout);
+	watchdog_stop_on_reboot(&priv->wdev);
+	watchdog_set_restart_priority(&priv->wdev, 128);
+
+	return devm_watchdog_register_device(dev, &priv->wdev);
+}
+
+static const struct of_device_id sp_wdt_of_match[] = {
+	{.compatible = "sunplus,sp7021-wdt", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, sp_wdt_of_match);
+
+static struct platform_driver sp_wdt_driver = {
+	.probe = sp_wdt_probe,
+	.driver = {
+		   .name = DEVICE_NAME,
+		   .of_match_table = sp_wdt_of_match,
+	},
+};
+
+module_platform_driver(sp_wdt_driver);
+
+MODULE_AUTHOR("Xiantao Hu <xt.hu@xxxxxxxxxxx>");
+MODULE_DESCRIPTION("Sunplus Watchdog Timer Driver");
+MODULE_LICENSE("GPL");
-- 
2.33.1