watchdog: npcm: Enable clock if provided

On the Nuvoton WPCM450 SoC, with its upcoming clock driver, peripheral
clocks are individually gated and ungated. Therefore, the watchdog
driver must be able to ungate the watchdog clock.

Signed-off-by: Jonathan Neuschäfer <[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: neuschaefer

drivers/watchdog/npcm_wdt.c

@@ -3,6 +3,7 @@
 // Copyright (c) 2018 IBM Corp.
 
 #include <linux/bitops.h>
+#include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
@@ -43,6 +44,7 @@
 struct npcm_wdt {
 	struct watchdog_device  wdd;
 	void __iomem		*reg;
+	struct clk		*clk;
 };
 
 static inline struct npcm_wdt *to_npcm_wdt(struct watchdog_device *wdd)
@@ -66,6 +68,9 @@ static int npcm_wdt_start(struct watchdog_device *wdd)
 	struct npcm_wdt *wdt = to_npcm_wdt(wdd);
 	u32 val;
 
+	if (wdt->clk)
+		clk_prepare_enable(wdt->clk);
+
 	if (wdd->timeout < 2)
 		val = 0x800;
 	else if (wdd->timeout < 3)
@@ -100,6 +105,9 @@ static int npcm_wdt_stop(struct watchdog_device *wdd)
 
 	writel(0, wdt->reg);
 
+	if (wdt->clk)
+		clk_disable_unprepare(wdt->clk);
+
 	return 0;
 }
 
@@ -147,6 +155,10 @@ static int npcm_wdt_restart(struct watchdog_device *wdd,
 {
 	struct npcm_wdt *wdt = to_npcm_wdt(wdd);
 
+	/* For reset, we start the WDT clock and leave it running. */
+	if (wdt->clk)
+		clk_prepare_enable(wdt->clk);
+
 	writel(NPCM_WTR | NPCM_WTRE | NPCM_WTE, wdt->reg);
 	udelay(1000);
 
@@ -191,6 +203,10 @@ static int npcm_wdt_probe(struct platform_device *pdev)
 	if (IS_ERR(wdt->reg))
 		return PTR_ERR(wdt->reg);
 
+	wdt->clk = devm_clk_get_optional(&pdev->dev, NULL);
+	if (IS_ERR(wdt->clk))
+		return PTR_ERR(wdt->clk);
+
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0)
 		return irq;