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Subject[tip:timers/core] clocksource/drivers/stm32: Factor out the timer width sorting code
Commit-ID:  70c62cf910aeba7cb79f4ebc7e6c8edbb37a77f6
Gitweb: https://git.kernel.org/tip/70c62cf910aeba7cb79f4ebc7e6c8edbb37a77f6
Author: Daniel Lezcano <daniel.lezcano@linaro.org>
AuthorDate: Mon, 8 Jan 2018 14:28:53 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 8 Jan 2018 17:57:25 +0100

clocksource/drivers/stm32: Factor out the timer width sorting code

In order to clarify and encapsulate the code for upcoming changes, move the
timer width check into a function and add some documentation.

Tested-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/1515418139-23276-14-git-send-email-daniel.lezcano@linaro.org
[ Spelling fixes. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
drivers/clocksource/timer-stm32.c | 30 +++++++++++++++++++++++-------
1 file changed, 23 insertions(+), 7 deletions(-)

diff --git a/drivers/clocksource/timer-stm32.c b/drivers/clocksource/timer-stm32.c
index 14b7a2b..33c7c90 100644
--- a/drivers/clocksource/timer-stm32.c
+++ b/drivers/clocksource/timer-stm32.c
@@ -80,9 +80,27 @@ static irqreturn_t stm32_clock_event_handler(int irq, void *dev_id)
return IRQ_HANDLED;
}

+/**
+ * stm32_timer_width - Sort out the timer width (32/16)
+ * @to: a pointer to a timer-of structure
+ *
+ * Write the 32-bit max value and read/return the result. If the timer
+ * is 32 bits wide, the result will be UINT_MAX, otherwise it will
+ * be truncated by the 16-bit register to USHRT_MAX.
+ *
+ * Returns UINT_MAX if the timer is 32 bits wide, USHRT_MAX if it is a
+ * 16 bits wide.
+ */
+static u32 __init stm32_timer_width(struct timer_of *to)
+{
+ writel_relaxed(UINT_MAX, timer_of_base(to) + TIM_ARR);
+
+ return readl_relaxed(timer_of_base(to) + TIM_ARR);
+}
+
static void __init stm32_clockevent_init(struct timer_of *to)
{
- unsigned long max_delta;
+ u32 width = 0;
int prescaler;

to->clkevt.name = to->np->full_name;
@@ -93,10 +111,8 @@ static void __init stm32_clockevent_init(struct timer_of *to)
to->clkevt.tick_resume = stm32_clock_event_shutdown;
to->clkevt.set_next_event = stm32_clock_event_set_next_event;

- /* Detect whether the timer is 16 or 32 bits */
- writel_relaxed(~0U, timer_of_base(to) + TIM_ARR);
- max_delta = readl_relaxed(timer_of_base(to) + TIM_ARR);
- if (max_delta == ~0U) {
+ width = stm32_timer_width(to);
+ if (width == UINT_MAX) {
prescaler = 1;
to->clkevt.rating = 250;
} else {
@@ -115,10 +131,10 @@ static void __init stm32_clockevent_init(struct timer_of *to)
to->of_clk.period = DIV_ROUND_UP(to->of_clk.rate, HZ);

clockevents_config_and_register(&to->clkevt,
- timer_of_rate(to), 0x1, max_delta);
+ timer_of_rate(to), 0x1, width);

pr_info("%pOF: STM32 clockevent driver initialized (%d bits)\n",
- to->np, max_delta == UINT_MAX ? 32 : 16);
+ to->np, width == UINT_MAX ? 32 : 16);
}

static int __init stm32_timer_init(struct device_node *node)
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