[PATCH v4 2/6] watchdog: npcm: Enable clock if provided

["Jonathan Neuschäfer" <j.neuschaefer@gmx.net>]

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 <j.neuschaefer@gmx.net>
---

v4:
- Don't disable clock in npcm_wdt_restart function

v3:
- https://lore.kernel.org/lkml/20220508194333.2170161-4-j.neuschaefer@gmx.net/
- Add enable/disable calls to npcm_wdt_restart handler
- Not applied due to the above change:  Acked-by: Guenter Roeck <linux@roeck-us.net>

v2:
- https://lore.kernel.org/lkml/20220429172030.398011-4-j.neuschaefer@gmx.net/
- Add clk_disable_unprepare call, suggested by Guenter Roeck

v1:
- https://lore.kernel.org/lkml/20220422183012.444674-4-j.neuschaefer@gmx.net/
---
 drivers/watchdog/npcm_wdt.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/watchdog/npcm_wdt.c b/drivers/watchdog/npcm_wdt.c
index 28a24caa2627c..a5dd1c2301374 100644
--- a/drivers/watchdog/npcm_wdt.c
+++ b/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;
--
2.35.1