watchdog: aspeed: Update bootstatus handling

The boot status in the watchdog device struct is updated during
controller probe stage. Application layer can get the boot status
through the command, cat /sys/class/watchdog/watchdogX/bootstatus.
The bootstatus can be,
WDIOF_CARDRESET => System is reset due to WDT timeout occurs.
Others          => Other reset events, e.g., power on reset.

On ASPEED platforms, boot status is recorded in the SCU registers.
- AST2400: Only a bit is used to represent system reset triggered by
           any WDT controller.
- AST2500/AST2600: System reset triggered by different WDT controllers
                   can be distinguished by different SCU bits.

Besides, on AST2400 and AST2500, since alternating boot event is
also triggered by using WDT timeout mechanism, it is classified
as WDIOF_CARDRESET.

Signed-off-by: Chin-Ting Kuo <[email protected]>
Reviewed-by: Andrew Jeffery <[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: chintingkuo

drivers/watchdog/aspeed_wdt.c

@@ -11,21 +11,30 @@
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/kstrtox.h>
+#include <linux/mfd/syscon.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_irq.h>
 #include <linux/platform_device.h>
+#include <linux/regmap.h>
 #include <linux/watchdog.h>
 
 static bool nowayout = WATCHDOG_NOWAYOUT;
 module_param(nowayout, bool, 0);
 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
 				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+struct aspeed_wdt_scu {
+	const char *compatible;
+	u32 reset_status_reg;
+	u32 wdt_reset_mask;
+	u32 wdt_reset_mask_shift;
+};
 
 struct aspeed_wdt_config {
 	u32 ext_pulse_width_mask;
 	u32 irq_shift;
 	u32 irq_mask;
+	struct aspeed_wdt_scu scu;
 };
 
 struct aspeed_wdt {
@@ -39,18 +48,36 @@ static const struct aspeed_wdt_config ast2400_config = {
 	.ext_pulse_width_mask = 0xff,
 	.irq_shift = 0,
 	.irq_mask = 0,
+	.scu = {
+		.compatible = "aspeed,ast2400-scu",
+		.reset_status_reg = 0x3c,
+		.wdt_reset_mask = 0x1,
+		.wdt_reset_mask_shift = 1,
+	},
 };
 
 static const struct aspeed_wdt_config ast2500_config = {
 	.ext_pulse_width_mask = 0xfffff,
 	.irq_shift = 12,
 	.irq_mask = GENMASK(31, 12),
+	.scu = {
+		.compatible = "aspeed,ast2500-scu",
+		.reset_status_reg = 0x3c,
+		.wdt_reset_mask = 0x1,
+		.wdt_reset_mask_shift = 2,
+	},
 };
 
 static const struct aspeed_wdt_config ast2600_config = {
 	.ext_pulse_width_mask = 0xfffff,
 	.irq_shift = 0,
 	.irq_mask = GENMASK(31, 10),
+	.scu = {
+		.compatible = "aspeed,ast2600-scu",
+		.reset_status_reg = 0x74,
+		.wdt_reset_mask = 0xf,
+		.wdt_reset_mask_shift = 16,
+	},
 };
 
 static const struct of_device_id aspeed_wdt_of_table[] = {
@@ -213,6 +240,56 @@ static int aspeed_wdt_restart(struct watchdog_device *wdd,
 	return 0;
 }
 
+static void aspeed_wdt_update_bootstatus(struct platform_device *pdev,
+					 struct aspeed_wdt *wdt)
+{
+	const struct resource *res;
+	struct aspeed_wdt_scu scu = wdt->cfg->scu;
+	struct regmap *scu_base;
+	u32 reset_mask_width;
+	u32 reset_mask_shift;
+	u32 idx = 0;
+	u32 status;
+	int ret;
+
+	if (!of_device_is_compatible(pdev->dev.of_node, "aspeed,ast2400-wdt")) {
+		res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+		idx = ((intptr_t)wdt->base & 0x00000fff) / resource_size(res);
+	}
+
+	scu_base = syscon_regmap_lookup_by_compatible(scu.compatible);
+	if (IS_ERR(scu_base)) {
+		wdt->wdd.bootstatus = WDIOS_UNKNOWN;
+		return;
+	}
+
+	ret = regmap_read(scu_base, scu.reset_status_reg, &status);
+	if (ret) {
+		wdt->wdd.bootstatus = WDIOS_UNKNOWN;
+		return;
+	}
+
+	reset_mask_width = hweight32(scu.wdt_reset_mask);
+	reset_mask_shift = scu.wdt_reset_mask_shift +
+			   reset_mask_width * idx;
+
+	if (status & (scu.wdt_reset_mask << reset_mask_shift))
+		wdt->wdd.bootstatus = WDIOF_CARDRESET;
+
+	/* clear wdt reset event flag */
+	if (of_device_is_compatible(pdev->dev.of_node, "aspeed,ast2400-wdt") ||
+	    of_device_is_compatible(pdev->dev.of_node, "aspeed,ast2500-wdt")) {
+		ret = regmap_read(scu_base, scu.reset_status_reg, &status);
+		if (!ret) {
+			status &= ~(scu.wdt_reset_mask << reset_mask_shift);
+			regmap_write(scu_base, scu.reset_status_reg, status);
+		}
+	} else {
+		regmap_write(scu_base, scu.reset_status_reg,
+			     scu.wdt_reset_mask << reset_mask_shift);
+	}
+}
+
 /* access_cs0 shows if cs0 is accessible, hence the reverted bit */
 static ssize_t access_cs0_show(struct device *dev,
 			       struct device_attribute *attr, char *buf)
@@ -458,10 +535,10 @@ static int aspeed_wdt_probe(struct platform_device *pdev)
 		writel(duration - 1, wdt->base + WDT_RESET_WIDTH);
 	}
 
+	aspeed_wdt_update_bootstatus(pdev, wdt);
+
 	status = readl(wdt->base + WDT_TIMEOUT_STATUS);
 	if (status & WDT_TIMEOUT_STATUS_BOOT_SECONDARY) {
-		wdt->wdd.bootstatus = WDIOF_CARDRESET;
-
 		if (of_device_is_compatible(np, "aspeed,ast2400-wdt") ||
 		    of_device_is_compatible(np, "aspeed,ast2500-wdt"))
 			wdt->wdd.groups = bswitch_groups;