[v6,3/5] clocksource: stm32: only use 32 bits timers

Commit Message

Benjamin Gaignard Oct. 18, 2017, 12:58 p.m. UTC

16 bits hardware are not enough accure to be used.
Do no allow them to be probed by tested max counter value.

Signed-off-by: Benjamin Gaignard <[e-mail]>
---
 drivers/clocksource/timer-stm32.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

Comments

Thomas Gleixner Oct. 18, 2017, 6:35 p.m. UTC | #1

On Wed, 18 Oct 2017, Benjamin Gaignard wrote:

> 16 bits hardware are not enough accure to be used.

That should probably read:

  16 bit counters are not accurate enough to be used.

Right?

> Do no allow them to be probed by tested max counter value.

I really do not understand why you want to do this. Accuracy is not really
a reason to dismiss working hardware right away. What you can do is to
lower the rating so other eventually available hardware will be preferred.

I might be missing something, but if so this is obviously missing in the
changelog.

Thanks,

	tglx

Patch

diff --git a/drivers/clocksource/timer-stm32.c b/drivers/clocksource/timer-stm32.c
index 67dcf48..c834648 100644
--- a/drivers/clocksource/timer-stm32.c
+++ b/drivers/clocksource/timer-stm32.c
@@ -81,9 +81,9 @@  static irqreturn_t stm32_clock_event_handler(int irq, void *dev_id)
 static int __init stm32_clockevent_init(struct device_node *node)
 {
 	struct reset_control *rstc;
-	unsigned long max_delta;
-	int ret, bits, prescaler = 1;
+	unsigned long max_arr;
 	struct timer_of *to;
+	int ret;
 
 	to = kzalloc(sizeof(*to), GFP_KERNEL);
 	if (!to)
@@ -113,29 +113,27 @@  static int __init stm32_clockevent_init(struct device_node *node)
 
 	/* 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) {
-		prescaler = 1;
-		bits = 32;
-	} else {
-		prescaler = 1024;
-		bits = 16;
+	max_arr = readl_relaxed(timer_of_base(to) + TIM_ARR);
+	if (max_arr != ~0U) {
+		pr_err("32 bits timer is needed\n");
+		ret = -EINVAL;
+		goto deinit;
 	}
+
 	writel_relaxed(0, timer_of_base(to) + TIM_ARR);
 
-	writel_relaxed(prescaler - 1, timer_of_base(to) + TIM_PSC);
+	writel_relaxed(0, timer_of_base(to) + TIM_PSC);
 	writel_relaxed(TIM_EGR_UG, timer_of_base(to) + TIM_EGR);
 	writel_relaxed(TIM_DIER_UIE, timer_of_base(to) + TIM_DIER);
 	writel_relaxed(0, timer_of_base(to) + TIM_SR);
 
 	clockevents_config_and_register(&to->clkevt,
-					timer_of_period(to), 0x60, max_delta);
-
-	pr_info("%pOF: STM32 clockevent driver initialized (%d bits)\n",
-			node, bits);
+					timer_of_period(to), 0x60, ~0U);
 
 	return 0;
 
+deinit:
+	timer_of_deinit(to);
 err:
 	kfree(to);
 	return ret;