[v3] watchdog: stm32_iwdg: Add pretimeout support

diff --git a/drivers/watchdog/stm32_iwdg.c b/drivers/watchdog/stm32_iwdg.c
index 5404e03876202..d700e0d49bb95 100644
--- a/drivers/watchdog/stm32_iwdg.c
+++ b/drivers/watchdog/stm32_iwdg.c
@@ -18,6 +18,7 @@ 
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/pm_wakeirq.h>
 #include <linux/watchdog.h>
 
 #define DEFAULT_TIMEOUT 10
@@ -28,6 +29,7 @@ 
 #define IWDG_RLR	0x08 /* ReLoad Register */
 #define IWDG_SR		0x0C /* Status Register */
 #define IWDG_WINR	0x10 /* Windows Register */
+#define IWDG_EWCR	0x14 /* Early Wake-up Register */
 
 /* IWDG_KR register bit mask */
 #define KR_KEY_RELOAD	0xAAAA /* reload counter enable */
@@ -47,22 +49,29 @@ 
 #define SR_PVU	BIT(0) /* Watchdog prescaler value update */
 #define SR_RVU	BIT(1) /* Watchdog counter reload value update */
 
+#define EWCR_EWIT	GENMASK(11, 0) /* Watchdog counter window value */
+#define EWCR_EWIC	BIT(14) /* Watchdog early interrupt acknowledge */
+#define EWCR_EWIE	BIT(15) /* Watchdog early interrupt enable */
+
 /* set timeout to 100000 us */
 #define TIMEOUT_US	100000
 #define SLEEP_US	1000
 
 struct stm32_iwdg_data {
 	bool has_pclk;
+	bool has_early_wakeup;
 	u32 max_prescaler;
 };
 
 static const struct stm32_iwdg_data stm32_iwdg_data = {
 	.has_pclk = false,
+	.has_early_wakeup = false,
 	.max_prescaler = 256,
 };
 
 static const struct stm32_iwdg_data stm32mp1_iwdg_data = {
 	.has_pclk = true,
+	.has_early_wakeup = true,
 	.max_prescaler = 1024,
 };
 
@@ -88,13 +97,18 @@  static inline void reg_write(void __iomem *base, u32 reg, u32 val)
 static int stm32_iwdg_start(struct watchdog_device *wdd)
 {
 	struct stm32_iwdg *wdt = watchdog_get_drvdata(wdd);
-	u32 tout, presc, iwdg_rlr, iwdg_pr, iwdg_sr;
+	u32 tout, ptot, presc, iwdg_rlr, iwdg_ewcr, iwdg_pr, iwdg_sr;
 	int ret;
 
 	dev_dbg(wdd->parent, "%s\n", __func__);
 
+	if (!wdd->pretimeout)
+		wdd->pretimeout = 3 * wdd->timeout / 4;
+
 	tout = clamp_t(unsigned int, wdd->timeout,
 		       wdd->min_timeout, wdd->max_hw_heartbeat_ms / 1000);
+	ptot = clamp_t(unsigned int, tout - wdd->pretimeout,
+		       wdd->min_timeout, tout);
 
 	presc = DIV_ROUND_UP(tout * wdt->rate, RLR_MAX + 1);
 
@@ -102,6 +116,7 @@  static int stm32_iwdg_start(struct watchdog_device *wdd)
 	presc = roundup_pow_of_two(presc);
 	iwdg_pr = presc <= 1 << PR_SHIFT ? 0 : ilog2(presc) - PR_SHIFT;
 	iwdg_rlr = ((tout * wdt->rate) / presc) - 1;
+	iwdg_ewcr = ((ptot * wdt->rate) / presc) - 1;
 
 	/* enable write access */
 	reg_write(wdt->regs, IWDG_KR, KR_KEY_EWA);
@@ -109,6 +124,8 @@  static int stm32_iwdg_start(struct watchdog_device *wdd)
 	/* set prescaler & reload registers */
 	reg_write(wdt->regs, IWDG_PR, iwdg_pr);
 	reg_write(wdt->regs, IWDG_RLR, iwdg_rlr);
+	if (wdt->data->has_early_wakeup)
+		reg_write(wdt->regs, IWDG_EWCR, iwdg_ewcr | EWCR_EWIE);
 	reg_write(wdt->regs, IWDG_KR, KR_KEY_ENABLE);
 
 	/* wait for the registers to be updated (max 100ms) */
@@ -151,6 +168,34 @@  static int stm32_iwdg_set_timeout(struct watchdog_device *wdd,
 	return 0;
 }
 
+static int stm32_iwdg_set_pretimeout(struct watchdog_device *wdd,
+				     unsigned int pretimeout)
+{
+	dev_dbg(wdd->parent, "%s pretimeout: %d sec\n", __func__, pretimeout);
+
+	wdd->pretimeout = pretimeout;
+
+	if (watchdog_active(wdd))
+		return stm32_iwdg_start(wdd);
+
+	return 0;
+}
+
+static irqreturn_t stm32_iwdg_isr(int irq, void *wdog_arg)
+{
+	struct watchdog_device *wdd = wdog_arg;
+	struct stm32_iwdg *wdt = watchdog_get_drvdata(wdd);
+	u32 reg;
+
+	reg = reg_read(wdt->regs, IWDG_EWCR);
+	reg |= EWCR_EWIC;
+	reg_write(wdt->regs, IWDG_EWCR, reg);
+
+	watchdog_notify_pretimeout(wdd);
+
+	return IRQ_HANDLED;
+}
+
 static void stm32_clk_disable_unprepare(void *data)
 {
 	clk_disable_unprepare(data);
@@ -207,11 +252,20 @@  static const struct watchdog_info stm32_iwdg_info = {
 	.identity	= "STM32 Independent Watchdog",
 };
 
+static const struct watchdog_info stm32_iwdg_preinfo = {
+	.options	= WDIOF_SETTIMEOUT |
+			  WDIOF_MAGICCLOSE |
+			  WDIOF_KEEPALIVEPING |
+			  WDIOF_PRETIMEOUT,
+	.identity	= "STM32 Independent Watchdog",
+};
+
 static const struct watchdog_ops stm32_iwdg_ops = {
 	.owner		= THIS_MODULE,
 	.start		= stm32_iwdg_start,
 	.ping		= stm32_iwdg_ping,
 	.set_timeout	= stm32_iwdg_set_timeout,
+	.set_pretimeout	= stm32_iwdg_set_pretimeout,
 };
 
 static const struct of_device_id stm32_iwdg_of_match[] = {
@@ -221,6 +275,40 @@  static const struct of_device_id stm32_iwdg_of_match[] = {
 };
 MODULE_DEVICE_TABLE(of, stm32_iwdg_of_match);
 
+static int stm32_iwdg_irq_init(struct platform_device *pdev,
+			       struct stm32_iwdg *wdt)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct watchdog_device *wdd = &wdt->wdd;
+	struct device *dev = &pdev->dev;
+	int irq, ret;
+
+	if (!wdt->data->has_early_wakeup)
+		return 0;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq <= 0)
+		return 0;
+
+	if (of_property_read_bool(np, "wakeup-source")) {
+		ret = device_init_wakeup(dev, true);
+		if (ret)
+			return ret;
+
+		ret = dev_pm_set_wake_irq(dev, irq);
+		if (ret)
+			return ret;
+	}
+
+	ret = devm_request_irq(dev, irq, stm32_iwdg_isr, 0,
+			       dev_name(dev), wdd);
+	if (ret)
+		return ret;
+
+	wdd->info = &stm32_iwdg_preinfo;
+	return 0;
+}
+
 static int stm32_iwdg_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -255,6 +343,11 @@  static int stm32_iwdg_probe(struct platform_device *pdev)
 	wdd->max_hw_heartbeat_ms = ((RLR_MAX + 1) * wdt->data->max_prescaler *
 				    1000) / wdt->rate;
 
+	/* Initialize IRQ, this might override wdd->info, hence it is here. */
+	ret = stm32_iwdg_irq_init(pdev, wdt);
+	if (ret)
+		return ret;
+
 	watchdog_set_drvdata(wdd, wdt);
 	watchdog_set_nowayout(wdd, WATCHDOG_NOWAYOUT);
 	watchdog_init_timeout(wdd, 0, dev);