clocksource/drivers/fttmr010: Optimize sched_clock()

The sched_clock() call should be really fast so we want to
avoid an extra if() clause on the read path if possible.

Implement two sched_clock_read() functions, one if the timer
counts up and one if it counts down. Incidentally this also
mirrors how clocksource_mmio_init() works and make things
simple and easy to understand.

Suggested-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Andrew Jeffery <andrew@aj.id.au>
Cc: Joel Stanley <joel@jms.id.au>
Cc: Jonas Jensen <jonas.jensen@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

diff --git a/drivers/clocksource/timer-fttmr010.c b/drivers/clocksource/timer-fttmr010.c
index a21020c..b56d7bd 100644 (file)
--- a/drivers/clocksource/timer-fttmr010.c
+++ b/drivers/clocksource/timer-fttmr010.c
@@ -91,13 +91,16 @@ static inline struct fttmr010 *to_fttmr010(struct clock_event_device *evt)
        return container_of(evt, struct fttmr010, clkevt);
 }
 
-static u64 notrace fttmr010_read_sched_clock(void)
+static u64 notrace fttmr010_read_sched_clock_up(void)
 {
-       if (local_fttmr->count_down)
-               return ~readl(local_fttmr->base + TIMER2_COUNT);
        return readl(local_fttmr->base + TIMER2_COUNT);
 }
 
+static u64 notrace fttmr010_read_sched_clock_down(void)
+{
+       return ~readl(local_fttmr->base + TIMER2_COUNT);
+}
+
 static int fttmr010_timer_set_next_event(unsigned long cycles,
                                       struct clock_event_device *evt)
 {
@@ -302,15 +305,17 @@ static int __init fttmr010_common_init(struct device_node *np, bool is_aspeed)
                                      "FTTMR010-TIMER2",
                                      fttmr010->tick_rate,
                                      300, 32, clocksource_mmio_readl_down);
+               sched_clock_register(fttmr010_read_sched_clock_down, 32,
+                                    fttmr010->tick_rate);
        } else {
                writel(0, fttmr010->base + TIMER2_LOAD);
                clocksource_mmio_init(fttmr010->base + TIMER2_COUNT,
                                      "FTTMR010-TIMER2",
                                      fttmr010->tick_rate,
                                      300, 32, clocksource_mmio_readl_up);
+               sched_clock_register(fttmr010_read_sched_clock_up, 32,
+                                    fttmr010->tick_rate);
        }
-       sched_clock_register(fttmr010_read_sched_clock, 32,
-                            fttmr010->tick_rate);
 
        /*
         * Setup clockevent timer (interrupt-driven) on timer 1.