[RFC PATCH 1/2] watchdog: imx2: fix hang-up on boot for i.MX21, i.MX27 and i.MX31 SoCs

[Vladimir Zapolskiy]

Power down counter enable/disable bit switch is located in WMCR
register, but watchdog controllers found on legacy i.MX21, i.MX27 and
i.MX31 SoCs don't have this register. As a result of writing data to
the non-existing register on driver probe the SoC hangs up, to fix the
problem add more OF compatible strings and on this basis get
information about availability of the WMCR register.

Fixes: 5fe65ce7ccbb ("watchdog: imx2_wdt: Disable power down counter on boot")
Signed-off-by: Vladimir Zapolskiy <vz at mleia.com>
---
 drivers/watchdog/imx2_wdt.c | 47 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 45 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
index 62f346b..b6763e0 100644
--- a/drivers/watchdog/imx2_wdt.c
+++ b/drivers/watchdog/imx2_wdt.c
@@ -29,6 +29,7 @@
 #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>
@@ -57,6 +58,10 @@
 
 #define WDOG_SEC_TO_COUNT(s)	((s * 2 - 1) << 8)
 
+struct imx2_wdt_data {
+	bool has_pdc;
+};
+
 struct imx2_wdt_device {
 	struct clk *clk;
 	struct regmap *regmap;
@@ -64,6 +69,8 @@ struct imx2_wdt_device {
 	bool ext_reset;
 };
 
+static const struct of_device_id imx2_wdt_dt_ids[];
+
 static bool nowayout = WATCHDOG_NOWAYOUT;
 module_param(nowayout, bool, 0);
 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
@@ -200,10 +207,13 @@ static const struct regmap_config imx2_wdt_regmap_config = {
 
 static int __init imx2_wdt_probe(struct platform_device *pdev)
 {
+	const struct of_device_id *of_id;
+	const struct imx2_wdt_data *data;
 	struct imx2_wdt_device *wdev;
 	struct watchdog_device *wdog;
 	struct resource *res;
 	void __iomem *base;
+	bool has_pdc;
 	int ret;
 	u32 val;
 
@@ -261,12 +271,24 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
 		set_bit(WDOG_HW_RUNNING, &wdog->status);
 	}
 
+	if (pdev->dev.of_node) {
+		of_id = of_match_device(imx2_wdt_dt_ids, &pdev->dev);
+		if (!of_id)
+			return -ENODEV;
+
+		data = of_id->data;
+		has_pdc = data->has_pdc;
+	} else {
+		has_pdc = false;
+	}
+
 	/*
 	 * Disable the watchdog power down counter at boot. Otherwise the power
 	 * down counter will pull down the #WDOG interrupt line for one clock
 	 * cycle.
 	 */
-	regmap_write(wdev->regmap, IMX2_WDT_WMCR, 0);
+	if (has_pdc)
+		regmap_write(wdev->regmap, IMX2_WDT_WMCR, 0);
 
 	ret = watchdog_register_device(wdog);
 	if (ret) {
@@ -363,8 +385,29 @@ static int imx2_wdt_resume(struct device *dev)
 static SIMPLE_DEV_PM_OPS(imx2_wdt_pm_ops, imx2_wdt_suspend,
 			 imx2_wdt_resume);
 
+static const struct imx2_wdt_data imx21_wdt_data = {
+	.has_pdc = false,
+};
+
+static const struct imx2_wdt_data imx25_wdt_data = {
+	.has_pdc = true,
+};
+
 static const struct of_device_id imx2_wdt_dt_ids[] = {
-	{ .compatible = "fsl,imx21-wdt", },
+	{ .compatible = "fsl,imx21-wdt",  .data = &imx21_wdt_data },
+	{ .compatible = "fsl,imx25-wdt",  .data = &imx25_wdt_data },
+	{ .compatible = "fsl,imx27-wdt",  .data = &imx21_wdt_data },
+	{ .compatible = "fsl,imx31-wdt",  .data = &imx21_wdt_data },
+	{ .compatible = "fsl,imx35-wdt",  .data = &imx25_wdt_data },
+	{ .compatible = "fsl,imx50-wdt",  .data = &imx25_wdt_data },
+	{ .compatible = "fsl,imx51-wdt",  .data = &imx25_wdt_data },
+	{ .compatible = "fsl,imx53-wdt",  .data = &imx25_wdt_data },
+	{ .compatible = "fsl,imx6q-wdt",  .data = &imx25_wdt_data },
+	{ .compatible = "fsl,imx6sl-wdt", .data = &imx25_wdt_data },
+	{ .compatible = "fsl,imx6sx-wdt", .data = &imx25_wdt_data },
+	{ .compatible = "fsl,imx6ul-wdt", .data = &imx25_wdt_data },
+	{ .compatible = "fsl,imx7d-wdt",  .data = &imx25_wdt_data },
+	{ .compatible = "fsl,vf610-wdt",  .data = &imx25_wdt_data },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, imx2_wdt_dt_ids);
-- 
2.8.1