watchdog: mt7621-wdt: avoid ralink architecture dependent code

MT7621 SoC has a system controller node. Watchdog need to access to reset
status register. Ralink architecture and related driver are old and from
the beggining they are using some architecture dependent operations for
accessing this shared registers through 'asm/mach-ralink/ralink_regs.h'
header file. However this is not ideal from a driver perspective which can
just access to the system controller registers in an arch independent way
using regmap syscon APIs. Update Kconfig accordingly to select new added
dependencies and allow driver to be compile tested.

Signed-off-by: Sergio Paracuellos <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

drivers/watchdog/Kconfig

···
 config MT7621_WDT
 	tristate "Mediatek SoC watchdog"
 	select WATCHDOG_CORE
-	depends on SOC_MT7620 || SOC_MT7621
+	select REGMAP_MMIO
+	select MFD_SYSCON
+	depends on SOC_MT7620 || SOC_MT7621 || COMPILE_TEST
 	help
 	  Hardware driver for the Mediatek/Ralink MT7621/8 SoC Watchdog Timer.
 

drivers/watchdog/mt7621_wdt.c

···
 #include <linux/moduleparam.h>
 #include <linux/platform_device.h>
 #include <linux/mod_devicetable.h>
-
-#include <asm/mach-ralink/ralink_regs.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
 
 #define SYSC_RSTSTAT			0x38
 #define WDT_RST_CAUSE			BIT(1)
···
 struct mt7621_wdt_data {
 	void __iomem *base;
 	struct reset_control *rst;
+	struct regmap *sysc;
 	struct watchdog_device wdt;
 };
 
···
 	return 0;
 }
 
-static int mt7621_wdt_bootcause(void)
+static int mt7621_wdt_bootcause(struct mt7621_wdt_data *d)
 {
-	if (rt_sysc_r32(SYSC_RSTSTAT) & WDT_RST_CAUSE)
+	u32 val;
+
+	regmap_read(d->sysc, SYSC_RSTSTAT, &val);
+	if (val & WDT_RST_CAUSE)
 		return WDIOF_CARDRESET;
 
 	return 0;
···
 
 static int mt7621_wdt_probe(struct platform_device *pdev)
 {
+	struct device_node *np = pdev->dev.of_node;
 	struct device *dev = &pdev->dev;
 	struct watchdog_device *mt7621_wdt;
 	struct mt7621_wdt_data *drvdata;
···
 	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
 	if (!drvdata)
 		return -ENOMEM;
+
+	drvdata->sysc = syscon_regmap_lookup_by_phandle(np, "mediatek,sysctl");
+	if (IS_ERR(drvdata->sysc)) {
+		drvdata->sysc = syscon_regmap_lookup_by_compatible("mediatek,mt7621-sysc");
+		if (IS_ERR(drvdata->sysc))
+			return PTR_ERR(drvdata->sysc);
+	}
 
 	drvdata->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(drvdata->base))
···
 	mt7621_wdt->max_timeout = 0xfffful / 1000;
 	mt7621_wdt->parent = dev;
 
-	mt7621_wdt->bootstatus = mt7621_wdt_bootcause();
+	mt7621_wdt->bootstatus = mt7621_wdt_bootcause(drvdata);
 
 	watchdog_init_timeout(mt7621_wdt, mt7621_wdt->max_timeout, dev);
 	watchdog_set_nowayout(mt7621_wdt, nowayout);