1 files changed, 57 insertions, 20 deletions

diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c
index f709962018ac..362fd229786d 100644
--- a/drivers/watchdog/sama5d4_wdt.c
+++ b/drivers/watchdog/sama5d4_wdt.c
@@ -6,6 +6,7 @@
  * Licensed under GPLv2.
  */
 
+#include <linux/delay.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
@@ -29,6 +30,7 @@ struct sama5d4_wdt {
 	struct watchdog_device	wdd;
 	void __iomem		*reg_base;
 	u32			mr;
+	unsigned long		last_ping;
 };
 
 static int wdt_timeout = WDT_DEFAULT_TIMEOUT;
@@ -44,11 +46,34 @@ MODULE_PARM_DESC(nowayout,
 	"Watchdog cannot be stopped once started (default="
 	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 
+#define wdt_enabled (!(wdt->mr & AT91_WDT_WDDIS))
+
 #define wdt_read(wdt, field) \
 	readl_relaxed((wdt)->reg_base + (field))
 
-#define wdt_write(wtd, field, val) \
-	writel_relaxed((val), (wdt)->reg_base + (field))
+/* 4 slow clock periods is 4/32768 = 122.07µs*/
+#define WDT_DELAY	usecs_to_jiffies(123)
+
+static void wdt_write(struct sama5d4_wdt *wdt, u32 field, u32 val)
+{
+	/*
+	 * WDT_CR and WDT_MR must not be modified within three slow clock
+	 * periods following a restart of the watchdog performed by a write
+	 * access in WDT_CR.
+	 */
+	while (time_before(jiffies, wdt->last_ping + WDT_DELAY))
+		usleep_range(30, 125);
+	writel_relaxed(val, wdt->reg_base + field);
+	wdt->last_ping = jiffies;
+}
+
+static void wdt_write_nosleep(struct sama5d4_wdt *wdt, u32 field, u32 val)
+{
+	if (time_before(jiffies, wdt->last_ping + WDT_DELAY))
+		udelay(123);
+	writel_relaxed(val, wdt->reg_base + field);
+	wdt->last_ping = jiffies;
+}
 
 static int sama5d4_wdt_start(struct watchdog_device *wdd)
 {
@@ -89,7 +114,16 @@ static int sama5d4_wdt_set_timeout(struct watchdog_device *wdd,
 	wdt->mr &= ~AT91_WDT_WDD;
 	wdt->mr |= AT91_WDT_SET_WDV(value);
 	wdt->mr |= AT91_WDT_SET_WDD(value);
-	wdt_write(wdt, AT91_WDT_MR, wdt->mr);
+
+	/*
+	 * WDDIS has to be 0 when updating WDD/WDV. The datasheet states: When
+	 * setting the WDDIS bit, and while it is set, the fields WDV and WDD
+	 * must not be modified.
+	 * If the watchdog is enabled, then the timeout can be updated. Else,
+	 * wait that the user enables it.
+	 */
+	if (wdt_enabled)
+		wdt_write(wdt, AT91_WDT_MR, wdt->mr & ~AT91_WDT_WDDIS);
 
 	wdd->timeout = timeout;
 
@@ -145,23 +179,21 @@ static int of_sama5d4_wdt_init(struct device_node *np, struct sama5d4_wdt *wdt)
 
 static int sama5d4_wdt_init(struct sama5d4_wdt *wdt)
 {
-	struct watchdog_device *wdd = &wdt->wdd;
-	u32 value = WDT_SEC2TICKS(wdd->timeout);
 	u32 reg;
-
 	/*
-	 * Because the fields WDV and WDD must not be modified when the WDDIS
-	 * bit is set, so clear the WDDIS bit before writing the WDT_MR.
+	 * When booting and resuming, the bootloader may have changed the
+	 * watchdog configuration.
+	 * If the watchdog is already running, we can safely update it.
+	 * Else, we have to disable it properly.
 	 */
-	reg = wdt_read(wdt, AT91_WDT_MR);
-	reg &= ~AT91_WDT_WDDIS;
-	wdt_write(wdt, AT91_WDT_MR, reg);
-
-	wdt->mr |= AT91_WDT_SET_WDD(value);
-	wdt->mr |= AT91_WDT_SET_WDV(value);
-
-	wdt_write(wdt, AT91_WDT_MR, wdt->mr);
-
+	if (wdt_enabled) {
+		wdt_write_nosleep(wdt, AT91_WDT_MR, wdt->mr);
+	} else {
+		reg = wdt_read(wdt, AT91_WDT_MR);
+		if (!(reg & AT91_WDT_WDDIS))
+			wdt_write_nosleep(wdt, AT91_WDT_MR,
+					  reg | AT91_WDT_WDDIS);
+	}
 	return 0;
 }
 
@@ -172,6 +204,7 @@ static int sama5d4_wdt_probe(struct platform_device *pdev)
 	struct resource *res;
 	void __iomem *regs;
 	u32 irq = 0;
+	u32 timeout;
 	int ret;
 
 	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
@@ -184,6 +217,7 @@ static int sama5d4_wdt_probe(struct platform_device *pdev)
 	wdd->ops = &sama5d4_wdt_ops;
 	wdd->min_timeout = MIN_WDT_TIMEOUT;
 	wdd->max_timeout = MAX_WDT_TIMEOUT;
+	wdt->last_ping = jiffies;
 
 	watchdog_set_drvdata(wdd, wdt);
 
@@ -221,6 +255,11 @@ static int sama5d4_wdt_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	timeout = WDT_SEC2TICKS(wdd->timeout);
+
+	wdt->mr |= AT91_WDT_SET_WDD(timeout);
+	wdt->mr |= AT91_WDT_SET_WDV(timeout);
+
 	ret = sama5d4_wdt_init(wdt);
 	if (ret)
 		return ret;
@@ -263,9 +302,7 @@ static int sama5d4_wdt_resume(struct device *dev)
 {
 	struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
 
-	wdt_write(wdt, AT91_WDT_MR, wdt->mr & ~AT91_WDT_WDDIS);
-	if (wdt->mr & AT91_WDT_WDDIS)
-		wdt_write(wdt, AT91_WDT_MR, wdt->mr);
+	sama5d4_wdt_init(wdt);
 
 	return 0;
 }