timekeeping: Add persistent_clock_exist flag
In current kernel, there are several places which need to check
whether there is a persistent clock for the platform. Current check
is done by calling the read_persistent_clock() and validating its
return value.
So one optimization is to do the check only once in timekeeping_init(),
and use a flag persistent_clock_exist to record it.
v2: Add a has_persistent_clock() helper function, as suggested by John.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index dfc7f87..b7a5841 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -28,6 +28,9 @@
/* flag for if timekeeping is suspended */
int __read_mostly timekeeping_suspended;
+/* Flag for if there is a persistent clock on this platform */
+bool __read_mostly persistent_clock_exist = false;
+
static inline void tk_normalize_xtime(struct timekeeper *tk)
{
while (tk->xtime_nsec >= ((u64)NSEC_PER_SEC << tk->shift)) {
@@ -609,12 +612,14 @@
struct timespec now, boot, tmp;
read_persistent_clock(&now);
+
if (!timespec_valid_strict(&now)) {
pr_warn("WARNING: Persistent clock returned invalid value!\n"
" Check your CMOS/BIOS settings.\n");
now.tv_sec = 0;
now.tv_nsec = 0;
- }
+ } else if (now.tv_sec || now.tv_nsec)
+ persistent_clock_exist = true;
read_boot_clock(&boot);
if (!timespec_valid_strict(&boot)) {
@@ -687,11 +692,12 @@
{
struct timekeeper *tk = &timekeeper;
unsigned long flags;
- struct timespec ts;
- /* Make sure we don't set the clock twice */
- read_persistent_clock(&ts);
- if (!(ts.tv_sec == 0 && ts.tv_nsec == 0))
+ /*
+ * Make sure we don't set the clock twice, as timekeeping_resume()
+ * already did it
+ */
+ if (has_persistent_clock())
return;
write_seqlock_irqsave(&tk->lock, flags);
