clocksource/drivers/arm_global_timer: Simplify prescaler register access

Use GENMASK() to define the prescaler mask and make the whole driver use
the mask (together with helpers such as FIELD_{GET,PREP,FIT}) instead of
needing an additional shift and max value constant.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20240225151336.2728533-4-martin.blumenstingl@googlemail.com

diff --git a/drivers/clocksource/arm_global_timer.c b/drivers/clocksource/arm_global_timer.c
index 4726a15b0afc16901cb1861daae0ea0e889e0296..ab1c8c2b66b887a8149d1dbc1d6d41428e22c7e9 100644 (file)
--- a/drivers/clocksource/arm_global_timer.c
+++ b/drivers/clocksource/arm_global_timer.c
@@ -9,6 +9,7 @@
 
 #include <linux/init.h>
 #include <linux/interrupt.h>
+#include <linux/bitfield.h>
 #include <linux/clocksource.h>
 #include <linux/clockchips.h>
 #include <linux/cpu.h>
@@ -31,10 +32,7 @@
 #define GT_CONTROL_COMP_ENABLE         BIT(1)  /* banked */
 #define GT_CONTROL_IRQ_ENABLE          BIT(2)  /* banked */
 #define GT_CONTROL_AUTO_INC            BIT(3)  /* banked */
-#define GT_CONTROL_PRESCALER_SHIFT      8
-#define GT_CONTROL_PRESCALER_MAX        0xFF
-#define GT_CONTROL_PRESCALER_MASK       (GT_CONTROL_PRESCALER_MAX << \
-                                        GT_CONTROL_PRESCALER_SHIFT)
+#define GT_CONTROL_PRESCALER_MASK      GENMASK(15, 8)
 
 #define GT_INT_STATUS  0x0c
 #define GT_INT_STATUS_EVENT_FLAG       BIT(0)
@@ -248,7 +246,7 @@ static void gt_write_presc(u32 psv)
 
        reg = readl(gt_base + GT_CONTROL);
        reg &= ~GT_CONTROL_PRESCALER_MASK;
-       reg |= psv << GT_CONTROL_PRESCALER_SHIFT;
+       reg |= FIELD_PREP(GT_CONTROL_PRESCALER_MASK, psv);
        writel(reg, gt_base + GT_CONTROL);
 }
 
@@ -257,8 +255,7 @@ static u32 gt_read_presc(void)
        u32 reg;
 
        reg = readl(gt_base + GT_CONTROL);
-       reg &= GT_CONTROL_PRESCALER_MASK;
-       return reg >> GT_CONTROL_PRESCALER_SHIFT;
+       return FIELD_GET(GT_CONTROL_PRESCALER_MASK, reg);
 }
 
 static void __init gt_delay_timer_init(void)
@@ -273,9 +270,9 @@ static int __init gt_clocksource_init(void)
        writel(0, gt_base + GT_COUNTER0);
        writel(0, gt_base + GT_COUNTER1);
        /* set prescaler and enable timer on all the cores */
-       writel(((CONFIG_ARM_GT_INITIAL_PRESCALER_VAL - 1) <<
-               GT_CONTROL_PRESCALER_SHIFT)
-              | GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
+       writel(FIELD_PREP(GT_CONTROL_PRESCALER_MASK,
+                         CONFIG_ARM_GT_INITIAL_PRESCALER_VAL - 1) |
+              GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
 
 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
        sched_clock_register(gt_sched_clock_read, 64, gt_target_rate);
@@ -301,7 +298,7 @@ static int gt_clk_rate_change_cb(struct notifier_block *nb,
                psv--;
 
                /* prescaler within legal range? */
-               if (psv > GT_CONTROL_PRESCALER_MAX)
+               if (!FIELD_FIT(GT_CONTROL_PRESCALER_MASK, psv))
                        return NOTIFY_BAD;
 
                /*