[PATCH V2 2/2] timer: imx-tpm: add imx tpm timer support

On Tue, Jun 13, 2017 at 10:19:47AM +0200, Alexander Stein wrote:

On Tuesday 13 June 2017 15:58:45, Dong Aisheng wrote:

quoted

diff --git a/drivers/clocksource/timer-imx-tpm.c

b/drivers/clocksource/timer-imx-tpm.c new file mode 100644
index 0000000..940a4f75

--- /dev/null
+++ b/drivers/clocksource/timer-imx-tpm.c

@@ -0,0 +1,227 @@

[...]
+static int tpm_set_next_event(unsigned long delta,
+				struct clock_event_device *evt)
+{
+	unsigned long next, now;
+
+	next = readl(timer_base + TPM_CNT) + delta;
+	writel(next, timer_base + TPM_C0V);
+	now = readl(timer_base + TPM_CNT);

What about:

quoted

now = readl(timer_base + TPM_CNT);
next = now + delta;
writel(next, timer_base + TPM_C0V);
return 0;

quoted

+	return (int)((next - now) <= 0) ? -ETIME : 0;

Can this error actually happen, even with your implementation?

Yes, i did observe some -ETIME when testing with nanosleep or
hrtimer during programing min_delta event, especially when system
is high loading. e.g. run GPU stress test.

Please also refer to another mail for details i just replied to Daniel.

Regards
Dong Aisheng