clocksource/drivers/stm32: Add oneshot mode
The stm32 timer block is able to have a counter and a comparator.
Instead of using the auto-reload register for periodic events, we switch
to oneshot mode by using the comparator register.
The timer is able to generate an interrupt when the counter overflows but
we don't want that as this counter will be use as a clocksource in the next
patches. So it is disabled by the UDIS bit of the control register.
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/1515418139-23276-16-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 928ac28..882037f 100644
--- a/drivers/clocksource/timer-stm32.c
+++ b/drivers/clocksource/timer-stm32.c
@@ -24,14 +24,18 @@
#define TIM_DIER 0x0c
#define TIM_SR 0x10
#define TIM_EGR 0x14
+#define TIM_CNT 0x24
#define TIM_PSC 0x28
#define TIM_ARR 0x2c
+#define TIM_CCR1 0x34
#define TIM_CR1_CEN BIT(0)
+#define TIM_CR1_UDIS BIT(1)
#define TIM_CR1_OPM BIT(3)
#define TIM_CR1_ARPE BIT(7)
#define TIM_DIER_UIE BIT(0)
+#define TIM_DIER_CC1IE BIT(1)
#define TIM_SR_UIF BIT(0)
@@ -40,21 +44,21 @@
#define TIM_PSC_MAX USHRT_MAX
#define TIM_PSC_CLKRATE 10000
+static void stm32_clock_event_disable(struct timer_of *to)
+{
+ writel_relaxed(0, timer_of_base(to) + TIM_DIER);
+}
+
+static void stm32_clock_event_enable(struct timer_of *to)
+{
+ writel_relaxed(TIM_CR1_UDIS | TIM_CR1_CEN, timer_of_base(to) + TIM_CR1);
+}
+
static int stm32_clock_event_shutdown(struct clock_event_device *clkevt)
{
struct timer_of *to = to_timer_of(clkevt);
- writel_relaxed(0, timer_of_base(to) + TIM_CR1);
-
- return 0;
-}
-
-static int stm32_clock_event_set_periodic(struct clock_event_device *clkevt)
-{
- struct timer_of *to = to_timer_of(clkevt);
-
- writel_relaxed(timer_of_period(to), timer_of_base(to) + TIM_ARR);
- writel_relaxed(TIM_CR1_ARPE | TIM_CR1_CEN, timer_of_base(to) + TIM_CR1);
+ stm32_clock_event_disable(to);
return 0;
}
@@ -63,10 +67,34 @@ static int stm32_clock_event_set_next_event(unsigned long evt,
struct clock_event_device *clkevt)
{
struct timer_of *to = to_timer_of(clkevt);
+ unsigned long now, next;
- writel_relaxed(evt, timer_of_base(to) + TIM_ARR);
- writel_relaxed(TIM_CR1_ARPE | TIM_CR1_OPM | TIM_CR1_CEN,
- timer_of_base(to) + TIM_CR1);
+ next = readl_relaxed(timer_of_base(to) + TIM_CNT) + evt;
+ writel_relaxed(next, timer_of_base(to) + TIM_CCR1);
+ now = readl_relaxed(timer_of_base(to) + TIM_CNT);
+
+ if ((next - now) > evt)
+ return -ETIME;
+
+ writel_relaxed(TIM_DIER_CC1IE, timer_of_base(to) + TIM_DIER);
+
+ return 0;
+}
+
+static int stm32_clock_event_set_periodic(struct clock_event_device *clkevt)
+{
+ struct timer_of *to = to_timer_of(clkevt);
+
+ stm32_clock_event_enable(to);
+
+ return stm32_clock_event_set_next_event(timer_of_period(to), clkevt);
+}
+
+static int stm32_clock_event_set_oneshot(struct clock_event_device *clkevt)
+{
+ struct timer_of *to = to_timer_of(clkevt);
+
+ stm32_clock_event_enable(to);
return 0;
}
@@ -78,6 +106,11 @@ static irqreturn_t stm32_clock_event_handler(int irq, void *dev_id)
writel_relaxed(0, timer_of_base(to) + TIM_SR);
+ if (clockevent_state_periodic(clkevt))
+ stm32_clock_event_set_periodic(clkevt);
+ else
+ stm32_clock_event_shutdown(clkevt);
+
clkevt->event_handler(clkevt);
return IRQ_HANDLED;
@@ -108,9 +141,10 @@ static void __init stm32_clockevent_init(struct timer_of *to)
to->clkevt.name = to->np->full_name;
to->clkevt.features = CLOCK_EVT_FEAT_PERIODIC;
+ to->clkevt.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
to->clkevt.set_state_shutdown = stm32_clock_event_shutdown;
to->clkevt.set_state_periodic = stm32_clock_event_set_periodic;
- to->clkevt.set_state_oneshot = stm32_clock_event_shutdown;
+ to->clkevt.set_state_oneshot = stm32_clock_event_set_oneshot;
to->clkevt.tick_resume = stm32_clock_event_shutdown;
to->clkevt.set_next_event = stm32_clock_event_set_next_event;
@@ -129,12 +163,10 @@ static void __init stm32_clockevent_init(struct timer_of *to)
prescaler = prescaler < TIM_PSC_MAX ? prescaler : TIM_PSC_MAX;
to->clkevt.rating = 100;
}
- writel_relaxed(0, timer_of_base(to) + TIM_ARR);
writel_relaxed(prescaler - 1, timer_of_base(to) + TIM_PSC);
writel_relaxed(TIM_EGR_UG, timer_of_base(to) + TIM_EGR);
writel_relaxed(0, timer_of_base(to) + TIM_SR);
- writel_relaxed(TIM_DIER_UIE, timer_of_base(to) + TIM_DIER);
/* Adjust rate and period given the prescaler value */
to->of_clk.rate = DIV_ROUND_CLOSEST(to->of_clk.rate, prescaler);
