clocksource/drivers/npcm: Fix GENMASK and timer operation

NPCM7XX_Tx_OPER GENMASK bits are wrong, fix them.

Hopefully the NPCM7XX_REG_TICR0 register reset value of those bits was 0,
so it did not cause an issue.

The function npcm7xx_timer_oneshot() reads the register
NPCM7XX_REG_TCSR0, modifies it and then reads it again overwriting the
previous changes. Remove the extra read which is pointless.

The function npcm7xx_timer_periodic() is correct but the code writes
to the NPCM7XX_REG_TICR0 register while it is dealing with the
NPCM7XX_REG_TCSR0 register, that is confusing. Separate the write to
the registers in the code for the sake of clarity.

Fixes: 1c00289 ("clocksource/drivers/npcm: Add NPCM7xx timer driver")
Signed-off-by: Avi Fishman <avifishman70@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/clocksource/timer-npcm7xx.c

@@ -32,7 +32,7 @@
 #define NPCM7XX_Tx_INTEN		BIT(29)
 #define NPCM7XX_Tx_COUNTEN		BIT(30)
 #define NPCM7XX_Tx_ONESHOT		0x0
-#define NPCM7XX_Tx_OPER			GENMASK(27, 3)
+#define NPCM7XX_Tx_OPER			GENMASK(28, 27)
 #define NPCM7XX_Tx_MIN_PRESCALE		0x1
 #define NPCM7XX_Tx_TDR_MASK_BITS	24
 #define NPCM7XX_Tx_MAX_CNT		0xFFFFFF
@@ -84,8 +84,6 @@ static int npcm7xx_timer_oneshot(struct clock_event_device *evt)
 
 	val = readl(timer_of_base(to) + NPCM7XX_REG_TCSR0);
 	val &= ~NPCM7XX_Tx_OPER;
-
-	val = readl(timer_of_base(to) + NPCM7XX_REG_TCSR0);
 	val |= NPCM7XX_START_ONESHOT_Tx;
 	writel(val, timer_of_base(to) + NPCM7XX_REG_TCSR0);
 
@@ -97,12 +95,11 @@ static int npcm7xx_timer_periodic(struct clock_event_device *evt)
 	struct timer_of *to = to_timer_of(evt);
 	u32 val;
 
+	writel(timer_of_period(to), timer_of_base(to) + NPCM7XX_REG_TICR0);
+
 	val = readl(timer_of_base(to) + NPCM7XX_REG_TCSR0);
 	val &= ~NPCM7XX_Tx_OPER;
-
-	writel(timer_of_period(to), timer_of_base(to) + NPCM7XX_REG_TICR0);
 	val |= NPCM7XX_START_PERIODIC_Tx;
-
 	writel(val, timer_of_base(to) + NPCM7XX_REG_TCSR0);
 
 	return 0;