[PATCH v4 2/2] watchdog: Add Spreadtrum watchdog driver

[Eric Long]

This patch adds the watchdog driver for Spreadtrum SC9860 platform.

Signed-off-by: Eric Long <eric.long@xxxxxxxxxxxxxx>
---
Changes since v3:
 - Update Kconfig SPRD_WATCHDOG help messages.
 - Correct the wrong spell words.
 - Rename SPRD_WDT_CNT_HIGH_VALUE as SPRD_WDT_CNT_HIGH_SHIFT.
 - Remove unused macor.
 - Update sprd_wdt_set_pretimeout() api.
 - Add wdt->wdd.timeout default value.
 - Use devm_watchdog_register_device() to register wdt device.
 - If module does not support NOWAYOUT, disable wdt when remove this driver.
 - Call sprd_wdt_disable() every wdt suspend.

Changes since v2:
 - Rename all the macors, add SPRD tag at the head of the macro names.
 - Rename SPRD_WDT_CLK as SPRD_WTC_CNT_STEP.
 - Remove the code which check timeout value at the wrong place.
 - Add min/max timeout value limit.
 - Remove set WDOG_HW_RUNNING status at sprd_wdt_enable().
 - Add timeout/pretimeout judgment when set them.
 - Support WATCHDOG_NOWAYOUT status.

Changes since v1:
 - Use pretimeout instead of own implementation.
 - Fix timeout loop when loading timeout values.
 - use the infrastructure to read and set "timeout-sec" property.
 - Add conditions when start or stop watchdog.
 - Change the position of enabling watchdog.
 - Other optimization.
---
 drivers/watchdog/Kconfig    |   8 +
 drivers/watchdog/Makefile   |   1 +
 drivers/watchdog/sprd_wdt.c | 420 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 429 insertions(+)
 create mode 100644 drivers/watchdog/sprd_wdt.c

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index c722cbf..3367a8c 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -787,6 +787,14 @@ config UNIPHIER_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called uniphier_wdt.
 
+config SPRD_WATCHDOG
+	tristate "Spreadtrum watchdog support"
+	depends on ARCH_SPRD || COMPILE_TEST
+	select WATCHDOG_CORE
+	help
+	  Say Y here to include watchdog timer supported
+	  by Spreadtrum system.
+
 # AVR32 Architecture
 
 config AT32AP700X_WDT
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 56adf9f..187cca2 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -87,6 +87,7 @@ obj-$(CONFIG_ASPEED_WATCHDOG) += aspeed_wdt.o
 obj-$(CONFIG_ZX2967_WATCHDOG) += zx2967_wdt.o
 obj-$(CONFIG_STM32_WATCHDOG) += stm32_iwdg.o
 obj-$(CONFIG_UNIPHIER_WATCHDOG) += uniphier_wdt.o
+obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
 
 # AVR32 Architecture
 obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o
diff --git a/drivers/watchdog/sprd_wdt.c b/drivers/watchdog/sprd_wdt.c
new file mode 100644
index 0000000..f760a98
--- /dev/null
+++ b/drivers/watchdog/sprd_wdt.c
@@ -0,0 +1,420 @@
+/*
+ * Spreadtrum watchdog driver
+ * Copyright (C) 2017 Spreadtrum - http://www.spreadtrum.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+#define SPRD_WDT_LOAD_LOW		0x0
+#define SPRD_WDT_LOAD_HIGH		0x4
+#define SPRD_WDT_CTRL			0x8
+#define SPRD_WDT_INT_CLR		0xc
+#define SPRD_WDT_INT_RAW		0x10
+#define SPRD_WDT_INT_MSK		0x14
+#define SPRD_WDT_CNT_LOW		0x18
+#define SPRD_WDT_CNT_HIGH		0x1c
+#define SPRD_WDT_LOCK			0x20
+#define SPRD_WDT_IRQ_LOAD_LOW		0x2c
+#define SPRD_WDT_IRQ_LOAD_HIGH		0x30
+
+/* WDT_CTRL */
+#define SPRD_WDT_INT_EN_BIT		BIT(0)
+#define SPRD_WDT_CNT_EN_BIT		BIT(1)
+#define SPRD_WDT_NEW_VER_EN		BIT(2)
+#define SPRD_WDT_RST_EN_BIT		BIT(3)
+
+/* WDT_INT_CLR */
+#define SPRD_WDT_INT_CLEAR_BIT		BIT(0)
+#define SPRD_WDT_RST_CLEAR_BIT		BIT(3)
+
+/* WDT_INT_RAW */
+#define SPRD_WDT_INT_RAW_BIT		BIT(0)
+#define SPRD_WDT_RST_RAW_BIT		BIT(3)
+#define SPRD_WDT_LD_BUSY_BIT		BIT(4)
+
+/* 1s equal to 32768 counter steps */
+#define SPRD_WDT_CNT_STEP		32768
+
+#define SPRD_WDT_UNLOCK_KEY		0xe551
+#define SPRD_WDT_MIN_TIMEOUT		3
+#define SPRD_WDT_MAX_TIMEOUT		60
+
+#define SPRD_WDT_CNT_HIGH_SHIFT		16
+#define SPRD_WDT_LOW_VALUE_MASK		GENMASK(15, 0)
+#define SPRD_WDT_LOAD_TIMEOUT		1000
+
+struct sprd_wdt {
+	void __iomem *base;
+	struct watchdog_device wdd;
+	struct clk *enable;
+	struct clk *rtc_enable;
+	unsigned int irq;
+};
+
+static inline struct sprd_wdt *to_sprd_wdt(struct watchdog_device *wdd)
+{
+	return container_of(wdd, struct sprd_wdt, wdd);
+}
+
+static inline void sprd_wdt_lock(void __iomem *addr)
+{
+	writel_relaxed(0x0, addr + SPRD_WDT_LOCK);
+}
+
+static inline void sprd_wdt_unlock(void __iomem *addr)
+{
+	writel_relaxed(SPRD_WDT_UNLOCK_KEY, addr + SPRD_WDT_LOCK);
+}
+
+static inline bool sprd_wdt_is_running(struct sprd_wdt *wdt)
+{
+	u32 val;
+
+	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
+	return val & SPRD_WDT_NEW_VER_EN;
+}
+
+static irqreturn_t sprd_wdt_isr(int irq, void *dev_id)
+{
+	struct sprd_wdt *wdt = (struct sprd_wdt *)dev_id;
+
+	sprd_wdt_unlock(wdt->base);
+	writel_relaxed(SPRD_WDT_INT_CLEAR_BIT, wdt->base + SPRD_WDT_INT_CLR);
+	sprd_wdt_lock(wdt->base);
+	watchdog_notify_pretimeout(&wdt->wdd);
+	return IRQ_HANDLED;
+}
+
+static u32 sprd_wdt_get_cnt_value(struct sprd_wdt *wdt)
+{
+	u32 val;
+
+	val = readl_relaxed(wdt->base + SPRD_WDT_CNT_HIGH) <<
+		SPRD_WDT_CNT_HIGH_SHIFT;
+	val |= readl_relaxed(wdt->base + SPRD_WDT_CNT_LOW) &
+		SPRD_WDT_LOW_VALUE_MASK;
+
+	return val;
+}
+
+static int sprd_wdt_load_value(struct sprd_wdt *wdt, u32 timeout,
+			       u32 pretimeout)
+{
+	u32 val, delay_cnt = 0;
+	u32 tmr_step = timeout * SPRD_WDT_CNT_STEP;
+	u32 prtmr_step = pretimeout * SPRD_WDT_CNT_STEP;
+
+	sprd_wdt_unlock(wdt->base);
+	writel_relaxed((tmr_step >> SPRD_WDT_CNT_HIGH_SHIFT) &
+		      SPRD_WDT_LOW_VALUE_MASK, wdt->base + SPRD_WDT_LOAD_HIGH);
+	writel_relaxed((tmr_step & SPRD_WDT_LOW_VALUE_MASK),
+		       wdt->base + SPRD_WDT_LOAD_LOW);
+	writel_relaxed((prtmr_step >> SPRD_WDT_CNT_HIGH_SHIFT) &
+			SPRD_WDT_LOW_VALUE_MASK,
+		       wdt->base + SPRD_WDT_IRQ_LOAD_HIGH);
+	writel_relaxed(prtmr_step & SPRD_WDT_LOW_VALUE_MASK,
+		       wdt->base + SPRD_WDT_IRQ_LOAD_LOW);
+	sprd_wdt_lock(wdt->base);
+
+	/*
+	 * Waiting the load value operation done,
+	 * it needs two or three RTC clock cycles.
+	 */
+	do {
+		val = readl_relaxed(wdt->base + SPRD_WDT_INT_RAW);
+		if (!(val & SPRD_WDT_LD_BUSY_BIT))
+			break;
+
+		cpu_relax();
+	} while (delay_cnt++ < SPRD_WDT_LOAD_TIMEOUT);
+
+	if (delay_cnt >= SPRD_WDT_LOAD_TIMEOUT)
+		return -EBUSY;
+	return 0;
+}
+
+static int sprd_wdt_enable(struct sprd_wdt *wdt)
+{
+	u32 val;
+	int ret;
+
+	ret = clk_prepare_enable(wdt->enable);
+	if (ret)
+		return ret;
+	ret = clk_prepare_enable(wdt->rtc_enable);
+	if (ret)
+		return ret;
+
+	sprd_wdt_unlock(wdt->base);
+	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
+	val |= SPRD_WDT_NEW_VER_EN;
+	writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
+	sprd_wdt_lock(wdt->base);
+	return 0;
+}
+
+static void sprd_wdt_disable(struct sprd_wdt *wdt)
+{
+	sprd_wdt_unlock(wdt->base);
+	writel_relaxed(0x0, wdt->base + SPRD_WDT_CTRL);
+	sprd_wdt_lock(wdt->base);
+
+	clk_disable_unprepare(wdt->rtc_enable);
+	clk_disable_unprepare(wdt->enable);
+}
+
+static int sprd_wdt_start(struct watchdog_device *wdd)
+{
+	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
+	u32 val;
+	int ret;
+
+	ret = sprd_wdt_load_value(wdt, wdd->timeout, wdd->pretimeout);
+	if (ret)
+		return ret;
+
+	sprd_wdt_unlock(wdt->base);
+	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
+	val |= SPRD_WDT_CNT_EN_BIT | SPRD_WDT_INT_EN_BIT | SPRD_WDT_RST_EN_BIT;
+	writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
+	sprd_wdt_lock(wdt->base);
+	set_bit(WDOG_HW_RUNNING, &wdd->status);
+
+	return 0;
+}
+
+static int sprd_wdt_stop(struct watchdog_device *wdd)
+{
+	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
+	u32 val;
+
+	sprd_wdt_unlock(wdt->base);
+	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
+	val &= ~(SPRD_WDT_CNT_EN_BIT | SPRD_WDT_RST_EN_BIT |
+		SPRD_WDT_INT_EN_BIT);
+	writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
+	sprd_wdt_lock(wdt->base);
+	return 0;
+}
+
+static int sprd_wdt_set_timeout(struct watchdog_device *wdd,
+				u32 timeout)
+{
+	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
+
+	if (timeout == wdd->timeout)
+		return 0;
+
+	wdd->timeout = timeout;
+
+	return sprd_wdt_load_value(wdt, timeout, wdd->pretimeout);
+}
+
+static int sprd_wdt_set_pretimeout(struct watchdog_device *wdd,
+				   u32 new_pretimeout)
+{
+	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
+
+	if (new_pretimeout < wdd->min_timeout)
+		return -EINVAL;
+
+	wdd->pretimeout = new_pretimeout;
+
+	return sprd_wdt_load_value(wdt, wdd->timeout, new_pretimeout);
+}
+
+static u32 sprd_wdt_get_timeleft(struct watchdog_device *wdd)
+{
+	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
+	u32 val;
+
+	val = sprd_wdt_get_cnt_value(wdt);
+	val = val / SPRD_WDT_CNT_STEP;
+
+	return val;
+}
+
+static const struct watchdog_ops sprd_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = sprd_wdt_start,
+	.stop = sprd_wdt_stop,
+	.set_timeout = sprd_wdt_set_timeout,
+	.set_pretimeout = sprd_wdt_set_pretimeout,
+	.get_timeleft = sprd_wdt_get_timeleft,
+};
+
+static const struct watchdog_info sprd_wdt_info = {
+	.options = WDIOF_SETTIMEOUT |
+		   WDIOF_PRETIMEOUT |
+		   WDIOF_MAGICCLOSE |
+		   WDIOF_KEEPALIVEPING,
+	.identity = "Spreadtrum Watchdog Timer",
+};
+
+static int sprd_wdt_probe(struct platform_device *pdev)
+{
+	struct resource *wdt_res;
+	struct sprd_wdt *wdt;
+	int ret;
+
+	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
+	if (!wdt)
+		return -ENOMEM;
+
+	wdt_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	wdt->base = devm_ioremap_resource(&pdev->dev, wdt_res);
+	if (IS_ERR(wdt->base)) {
+		dev_err(&pdev->dev, "failed to map memory resource\n");
+		return PTR_ERR(wdt->base);
+	}
+
+	wdt->enable = devm_clk_get(&pdev->dev, "enable");
+	if (IS_ERR(wdt->enable)) {
+		dev_err(&pdev->dev, "can't get the enable clock\n");
+		return PTR_ERR(wdt->enable);
+	}
+
+	wdt->rtc_enable = devm_clk_get(&pdev->dev, "rtc_enable");
+	if (IS_ERR(wdt->rtc_enable)) {
+		dev_err(&pdev->dev, "can't get the rtc enable clock\n");
+		return PTR_ERR(wdt->rtc_enable);
+	}
+
+	wdt->irq = platform_get_irq(pdev, 0);
+	if (wdt->irq < 0) {
+		dev_err(&pdev->dev, "failed to get IRQ resource\n");
+		return wdt->irq;
+	}
+
+	ret = devm_request_irq(&pdev->dev, wdt->irq, sprd_wdt_isr,
+			       IRQF_NO_SUSPEND, "sprd-wdt", (void *)wdt);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register irq\n");
+		return ret;
+	}
+
+	wdt->wdd.info = &sprd_wdt_info;
+	wdt->wdd.ops = &sprd_wdt_ops;
+	wdt->wdd.parent = &pdev->dev;
+	wdt->wdd.min_timeout = SPRD_WDT_MIN_TIMEOUT;
+	wdt->wdd.max_timeout = SPRD_WDT_MAX_TIMEOUT;
+	wdt->wdd.timeout = SPRD_WDT_MAX_TIMEOUT;
+
+	ret = sprd_wdt_enable(wdt);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to enable wdt\n");
+		return ret;
+	}
+
+	watchdog_set_nowayout(&wdt->wdd, WATCHDOG_NOWAYOUT);
+	watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
+
+	ret = devm_watchdog_register_device(&pdev->dev, &wdt->wdd);
+	if (ret) {
+		sprd_wdt_disable(wdt);
+		dev_err(&pdev->dev, "failed to register watchdog\n");
+		return ret;
+	}
+	platform_set_drvdata(pdev, wdt);
+
+	return 0;
+}
+
+static int sprd_wdt_remove(struct platform_device *pdev)
+{
+	struct sprd_wdt *wdt = platform_get_drvdata(pdev);
+
+	/*
+	 * If set WDOG_NO_WAY_OUT bit, do not need disable wdt and
+	 * just let the system reboot when removing watchdog device.
+	 * Otherwise stop and disable the watchdog.
+	 */
+	if (!test_bit(WDOG_NO_WAY_OUT, &wdt->wdd.status)) {
+		if (watchdog_active(&wdt->wdd))
+			sprd_wdt_stop(&wdt->wdd);
+		sprd_wdt_disable(wdt);
+		return 0;
+	}
+
+	if (sprd_wdt_is_running(wdt))
+		dev_crit(&pdev->dev, "Device removed: Expect reboot!\n");
+	return 0;
+}
+
+static int __maybe_unused sprd_wdt_pm_suspend(struct device *dev)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+	struct sprd_wdt *wdt = dev_get_drvdata(dev);
+
+	if (watchdog_active(wdd))
+		sprd_wdt_stop(&wdt->wdd);
+	sprd_wdt_disable(wdt);
+
+	return 0;
+}
+
+static int __maybe_unused sprd_wdt_pm_resume(struct device *dev)
+{
+	struct watchdog_device *wdd = dev_get_drvdata(dev);
+	struct sprd_wdt *wdt = dev_get_drvdata(dev);
+	int ret;
+
+	ret = sprd_wdt_enable(wdt);
+	if (ret)
+		return ret;
+
+	if (watchdog_active(wdd)) {
+		ret = sprd_wdt_start(&wdt->wdd);
+		if (ret) {
+			sprd_wdt_disable(wdt);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+static const struct dev_pm_ops sprd_wdt_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(sprd_wdt_pm_suspend,
+				sprd_wdt_pm_resume)
+};
+
+static const struct of_device_id sprd_wdt_match_table[] = {
+	{ .compatible = "sprd,sp9860-wdt", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, sprd_wdt_match_table);
+
+static struct platform_driver sprd_watchdog_driver = {
+	.probe	= sprd_wdt_probe,
+	.remove	= sprd_wdt_remove,
+	.driver	= {
+		.name = "sprd-wdt",
+		.of_match_table = sprd_wdt_match_table,
+		.pm = &sprd_wdt_pm_ops,
+	},
+};
+module_platform_driver(sprd_watchdog_driver);
+
+MODULE_AUTHOR("Eric Long <eric.long@xxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Spreadtrum Watchdog Timer Controller Driver");
+MODULE_LICENSE("GPL v2");
-- 
1.9.1