watchdog: imx93: add watchdog timer on imx93

The WDOG clocks are sourced from lpo_clk, and lpo_clk is the fixed
32KHz. TOVAL contains the 16-bit value used to set the timeout period of
the watchdog. When the timeout period exceeds 2 seconds, the value
written to the TOVAL register is larger than 16-bit can represent.
Enabling watchdog prescaler can solve this problem.

Two points need to be aware of:
1. watchdog prescaler enables a fixed 256 pre-scaling of watchdog
counter reference clock
2. reconfiguration takes about 55ms on imx93

Reviewed-by: Jacky Bai <[email protected]>
Signed-off-by: Alice Guo <[email protected]>
Reviewed-by: Guenter Roeck <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Guenter Roeck <[email protected]>
Signed-off-by: Wim Van Sebroeck <[email protected]>

Author: Alice Guo

drivers/watchdog/imx7ulp_wdt.c

@@ -9,6 +9,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/reboot.h>
 #include <linux/watchdog.h>
@@ -52,11 +53,17 @@ module_param(nowayout, bool, 0000);
 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
 		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 
+struct imx_wdt_hw_feature {
+	bool prescaler_enable;
+	u32 wdog_clock_rate;
+};
+
 struct imx7ulp_wdt_device {
 	struct watchdog_device wdd;
 	void __iomem *base;
 	struct clk *clk;
 	bool post_rcs_wait;
+	const struct imx_wdt_hw_feature *hw;
 };
 
 static int imx7ulp_wdt_wait_ulk(void __iomem *base)
@@ -179,7 +186,7 @@ static int imx7ulp_wdt_set_timeout(struct watchdog_device *wdog,
 				   unsigned int timeout)
 {
 	struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
-	u32 toval = WDOG_CLOCK_RATE * timeout;
+	u32 toval = wdt->hw->wdog_clock_rate * timeout;
 	u32 val;
 	int ret;
 	u32 loop = RETRY_MAX;
@@ -276,6 +283,9 @@ static int imx7ulp_wdt_init(struct imx7ulp_wdt_device *wdt, unsigned int timeout
 	int ret;
 	u32 loop = RETRY_MAX;
 
+	if (wdt->hw->prescaler_enable)
+		val |= WDOG_CS_PRES;
+
 	do {
 		ret = _imx7ulp_wdt_init(wdt, timeout, val);
 		toval = readl(wdt->base + WDOG_TOVAL);
@@ -346,7 +356,9 @@ static int imx7ulp_wdt_probe(struct platform_device *pdev)
 	watchdog_stop_on_reboot(wdog);
 	watchdog_stop_on_unregister(wdog);
 	watchdog_set_drvdata(wdog, imx7ulp_wdt);
-	ret = imx7ulp_wdt_init(imx7ulp_wdt, wdog->timeout * WDOG_CLOCK_RATE);
+
+	imx7ulp_wdt->hw = of_device_get_match_data(dev);
+	ret = imx7ulp_wdt_init(imx7ulp_wdt, wdog->timeout * imx7ulp_wdt->hw->wdog_clock_rate);
 	if (ret)
 		return ret;
 
@@ -368,7 +380,7 @@ static int __maybe_unused imx7ulp_wdt_suspend_noirq(struct device *dev)
 static int __maybe_unused imx7ulp_wdt_resume_noirq(struct device *dev)
 {
 	struct imx7ulp_wdt_device *imx7ulp_wdt = dev_get_drvdata(dev);
-	u32 timeout = imx7ulp_wdt->wdd.timeout * WDOG_CLOCK_RATE;
+	u32 timeout = imx7ulp_wdt->wdd.timeout * imx7ulp_wdt->hw->wdog_clock_rate;
 	int ret;
 
 	ret = clk_prepare_enable(imx7ulp_wdt->clk);
@@ -389,9 +401,20 @@ static const struct dev_pm_ops imx7ulp_wdt_pm_ops = {
 				      imx7ulp_wdt_resume_noirq)
 };
 
+static const struct imx_wdt_hw_feature imx7ulp_wdt_hw = {
+	.prescaler_enable = false,
+	.wdog_clock_rate = 1000,
+};
+
+static const struct imx_wdt_hw_feature imx93_wdt_hw = {
+	.prescaler_enable = true,
+	.wdog_clock_rate = 125,
+};
+
 static const struct of_device_id imx7ulp_wdt_dt_ids[] = {
-	{ .compatible = "fsl,imx8ulp-wdt", },
-	{ .compatible = "fsl,imx7ulp-wdt", },
+	{ .compatible = "fsl,imx8ulp-wdt", .data = &imx7ulp_wdt_hw, },
+	{ .compatible = "fsl,imx7ulp-wdt", .data = &imx7ulp_wdt_hw, },
+	{ .compatible = "fsl,imx93-wdt", .data = &imx93_wdt_hw, },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, imx7ulp_wdt_dt_ids);