clocksource/drivers/stm32: Add clocksource functionality

The scene is set for the clocksource functionality, let's add it for this driver.

Tested-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1515418139-23276-18-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/drivers/clocksource/timer-stm32.c b/drivers/clocksource/timer-stm32.c
index 0d37f1a1994e8502d3bffcb23a7044c0e4a1c7aa..21b7492c963adeaf386ee012664f10be82af7e95 100644 (file)
--- a/drivers/clocksource/timer-stm32.c
+++ b/drivers/clocksource/timer-stm32.c
@@ -16,6 +16,7 @@
 #include <linux/of_irq.h>
 #include <linux/clk.h>
 #include <linux/reset.h>
+#include <linux/sched_clock.h>
 #include <linux/slab.h>
 
 #include "timer-of.h"
@@ -80,6 +81,13 @@ static int stm32_timer_of_bits_get(struct timer_of *to)
        return pd->bits;
 }
 
+static void __iomem *stm32_timer_cnt __read_mostly;
+
+static u64 notrace stm32_read_sched_clock(void)
+{
+       return readl_relaxed(stm32_timer_cnt);
+}
+
 static void stm32_clock_event_disable(struct timer_of *to)
 {
        writel_relaxed(0, timer_of_base(to) + TIM_DIER);
@@ -204,6 +212,31 @@ static void __init stm32_timer_set_prescaler(struct timer_of *to)
        to->of_clk.period = DIV_ROUND_UP(to->of_clk.rate, HZ);
 }
 
+static int __init stm32_clocksource_init(struct timer_of *to)
+{
+        u32 bits = stm32_timer_of_bits_get(to);
+       const char *name = to->np->full_name;
+
+       /*
+        * This driver allows to register several timers and relies on
+        * the generic time framework to select the right one.
+        * However, nothing allows to do the same for the
+        * sched_clock. We are not interested in a sched_clock for the
+        * 16-bit timers but only for the 32-bit one, so if no 32-bit
+        * timer is registered yet, we select this 32-bit timer as a
+        * sched_clock.
+        */
+       if (bits == 32 && !stm32_timer_cnt) {
+               stm32_timer_cnt = timer_of_base(to) + TIM_CNT;
+               sched_clock_register(stm32_read_sched_clock, bits, timer_of_rate(to));
+               pr_info("%s: STM32 sched_clock registered\n", name);
+       }
+
+       return clocksource_mmio_init(timer_of_base(to) + TIM_CNT, name,
+                                    timer_of_rate(to), bits == 32 ? 250 : 100,
+                                    bits, clocksource_mmio_readl_up);
+}
+
 static void __init stm32_clockevent_init(struct timer_of *to)
 {
        u32 bits = stm32_timer_of_bits_get(to);
@@ -256,6 +289,10 @@ static int __init stm32_timer_init(struct device_node *node)
 
        stm32_timer_set_prescaler(to);
 
+       ret = stm32_clocksource_init(to);
+       if (ret)
+               goto deinit;
+
        stm32_clockevent_init(to);
        return 0;