[PATCH v3 1/3] watchdog: imx2_wdg: suspend watchdog in WAIT mode

[Andrej Picej <andrej.picej@norik.com>]

Putting device into the "Suspend-To-Idle" mode causes watchdog to
trigger and resets the board after set watchdog timeout period elapses.

Introduce new device-tree property "fsl,suspend-in-wait" which suspends
watchdog in WAIT mode. This is done by setting WDW bit in WCR
(Watchdog Control Register). Watchdog operation is restored after
exiting WAIT mode as expected. WAIT mode corresponds with Linux's
"Suspend-To-Idle".

Signed-off-by: Andrej Picej <andrej.picej@norik.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
---
Changes in v3:
 - fix spelling in commit message,
 - fix and simplify property handling in probe,
 - add a comment about unknown interaction between imx7d no-ping
   functionality and "fsl,suspend-in-wait",
 - property support handled by of_device_id data pointer.

Changes in v2:
 - validate the property with compatible string, as this functionality
   is not supported by all devices.
---
 drivers/watchdog/imx2_wdt.c | 55 +++++++++++++++++++++++++++++++++++--
 1 file changed, 52 insertions(+), 3 deletions(-)

diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
index d0c5d47ddede..19ab7b3d286b 100644
--- a/drivers/watchdog/imx2_wdt.c
+++ b/drivers/watchdog/imx2_wdt.c
@@ -27,6 +27,7 @@
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/of_address.h>
+#include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
 #include <linux/watchdog.h>
@@ -35,6 +36,7 @@
 
 #define IMX2_WDT_WCR		0x00		/* Control Register */
 #define IMX2_WDT_WCR_WT		(0xFF << 8)	/* -> Watchdog Timeout Field */
+#define IMX2_WDT_WCR_WDW	BIT(7)		/* -> Watchdog disable for WAIT */
 #define IMX2_WDT_WCR_WDA	BIT(5)		/* -> External Reset WDOG_B */
 #define IMX2_WDT_WCR_SRS	BIT(4)		/* -> Software Reset Signal */
 #define IMX2_WDT_WCR_WRE	BIT(3)		/* -> WDOG Reset Enable */
@@ -60,13 +62,19 @@
 
 #define WDOG_SEC_TO_COUNT(s)	((s * 2 - 1) << 8)
 
+struct imx2_wdt_data {
+	bool wdw_supported;
+};
+
 struct imx2_wdt_device {
 	struct clk *clk;
 	struct regmap *regmap;
 	struct watchdog_device wdog;
+	const struct imx2_wdt_data *data;
 	bool ext_reset;
 	bool clk_is_on;
 	bool no_ping;
+	bool sleep_wait;
 };
 
 static bool nowayout = WATCHDOG_NOWAYOUT;
@@ -129,6 +137,9 @@ static inline void imx2_wdt_setup(struct watchdog_device *wdog)
 
 	/* Suspend timer in low power mode, write once-only */
 	val |= IMX2_WDT_WCR_WDZST;
+	/* Suspend timer in low power WAIT mode, write once-only */
+	if (wdev->sleep_wait)
+		val |= IMX2_WDT_WCR_WDW;
 	/* Strip the old watchdog Time-Out value */
 	val &= ~IMX2_WDT_WCR_WT;
 	/* Generate internal chip-level reset if WDOG times out */
@@ -292,6 +303,8 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
 	wdog->max_hw_heartbeat_ms = IMX2_WDT_MAX_TIME * 1000;
 	wdog->parent		= dev;
 
+	wdev->data = of_device_get_match_data(dev);
+
 	ret = platform_get_irq(pdev, 0);
 	if (ret > 0)
 		if (!devm_request_irq(dev, ret, imx2_wdt_isr, 0,
@@ -313,9 +326,18 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
 
 	wdev->ext_reset = of_property_read_bool(dev->of_node,
 						"fsl,ext-reset-output");
+
+	if (of_property_read_bool(dev->of_node, "fsl,suspend-in-wait")) {
+		if (!wdev->data->wdw_supported) {
+			dev_err(dev, "suspend-in-wait not supported\n");
+			return -EINVAL;
+		}
+		wdev->sleep_wait = true;
+	}
+
 	/*
 	 * The i.MX7D doesn't support low power mode, so we need to ping the watchdog
-	 * during suspend.
+	 * during suspend. Interaction with "fsl,suspend-in-wait" is unknown!
 	 */
 	wdev->no_ping = !of_device_is_compatible(dev->of_node, "fsl,imx7d-wdt");
 	platform_set_drvdata(pdev, wdog);
@@ -417,9 +439,36 @@ static int __maybe_unused imx2_wdt_resume(struct device *dev)
 static SIMPLE_DEV_PM_OPS(imx2_wdt_pm_ops, imx2_wdt_suspend,
 			 imx2_wdt_resume);
 
+struct imx2_wdt_data imx_wdt = {
+	.wdw_supported = true,
+};
+
+struct imx2_wdt_data imx_wdt_legacy = {
+	.wdw_supported = false,
+};
+
 static const struct of_device_id imx2_wdt_dt_ids[] = {
-	{ .compatible = "fsl,imx21-wdt", },
-	{ .compatible = "fsl,imx7d-wdt", },
+	{ .compatible = "fsl,imx21-wdt", .data = &imx_wdt_legacy },
+	{ .compatible = "fsl,imx25-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx27-wdt", .data = &imx_wdt_legacy },
+	{ .compatible = "fsl,imx31-wdt", .data = &imx_wdt_legacy },
+	{ .compatible = "fsl,imx35-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx50-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx51-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx53-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx6q-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx6sl-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx6sll-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx6sx-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx6ul-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx7d-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx8mm-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx8mn-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx8mp-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,imx8mq-wdt", .data = &imx_wdt },
+	{ .compatible = "fsl,ls1012a-wdt", .data = &imx_wdt_legacy },
+	{ .compatible = "fsl,ls1043a-wdt", .data = &imx_wdt_legacy },
+	{ .compatible = "fsl,vf610-wdt", .data = &imx_wdt },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, imx2_wdt_dt_ids);
-- 
2.25.1