watchdog: orion: Use atomic access for shared registers

Since the timer control register is shared with the clocksource driver,
use the recently introduced atomic_io_clear_set() to access such register.
Given the watchdog core already provides serialization for all the
watchdog ops, this commit allows to remove the spinlock entirely.

Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Tested-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Acked-by: Wim Van Sebroeck <wim@iguana.be>
Tested-By: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

drivers/watchdog/orion_wdt.c

@@ -20,7 +20,6 @@
 #include <linux/watchdog.h>
 #include <linux/init.h>
 #include <linux/io.h>
-#include <linux/spinlock.h>
 #include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/of.h>
@@ -46,25 +45,16 @@ static unsigned int wdt_max_duration;	/* (seconds) */
 static struct clk *clk;
 static unsigned int wdt_tclk;
 static void __iomem *wdt_reg;
-static DEFINE_SPINLOCK(wdt_lock);
 
 static int orion_wdt_ping(struct watchdog_device *wdt_dev)
 {
-	spin_lock(&wdt_lock);
-
 	/* Reload watchdog duration */
 	writel(wdt_tclk * wdt_dev->timeout, wdt_reg + WDT_VAL);
-
-	spin_unlock(&wdt_lock);
 	return 0;
 }
 
 static int orion_wdt_start(struct watchdog_device *wdt_dev)
 {
-	u32 reg;
-
-	spin_lock(&wdt_lock);
-
 	/* Set watchdog duration */
 	writel(wdt_tclk * wdt_dev->timeout, wdt_reg + WDT_VAL);
 
@@ -72,48 +62,26 @@ static int orion_wdt_start(struct watchdog_device *wdt_dev)
 	writel(~WDT_INT_REQ, BRIDGE_CAUSE);
 
 	/* Enable watchdog timer */
-	reg = readl(wdt_reg + TIMER_CTRL);
-	reg |= WDT_EN;
-	writel(reg, wdt_reg + TIMER_CTRL);
+	atomic_io_modify(wdt_reg + TIMER_CTRL, WDT_EN, WDT_EN);
 
 	/* Enable reset on watchdog */
-	reg = readl(RSTOUTn_MASK);
-	reg |= WDT_RESET_OUT_EN;
-	writel(reg, RSTOUTn_MASK);
-
-	spin_unlock(&wdt_lock);
+	atomic_io_modify(RSTOUTn_MASK, WDT_RESET_OUT_EN, WDT_RESET_OUT_EN);
 	return 0;
 }
 
 static int orion_wdt_stop(struct watchdog_device *wdt_dev)
 {
-	u32 reg;
-
-	spin_lock(&wdt_lock);
-
 	/* Disable reset on watchdog */
-	reg = readl(RSTOUTn_MASK);
-	reg &= ~WDT_RESET_OUT_EN;
-	writel(reg, RSTOUTn_MASK);
+	atomic_io_modify(RSTOUTn_MASK, WDT_RESET_OUT_EN, 0);
 
 	/* Disable watchdog timer */
-	reg = readl(wdt_reg + TIMER_CTRL);
-	reg &= ~WDT_EN;
-	writel(reg, wdt_reg + TIMER_CTRL);
-
-	spin_unlock(&wdt_lock);
+	atomic_io_modify(wdt_reg + TIMER_CTRL, WDT_EN, 0);
 	return 0;
 }
 
 static unsigned int orion_wdt_get_timeleft(struct watchdog_device *wdt_dev)
 {
-	unsigned int time_left;
-
-	spin_lock(&wdt_lock);
-	time_left = readl(wdt_reg + WDT_VAL) / wdt_tclk;
-	spin_unlock(&wdt_lock);
-
-	return time_left;
+	return readl(wdt_reg + WDT_VAL) / wdt_tclk;
 }
 
 static int orion_wdt_set_timeout(struct watchdog_device *wdt_dev,