timekeeping: Zero initialize system_counterval when querying time from phc drivers

Most drivers only populate the fields cycles and cs_id of system_counterval
in their get_time_fn() callback for get_device_system_crosststamp(), unless
they explicitly provide nanosecond values.

When the use_nsecs field was added to struct system_counterval, most
drivers did not care.  Clock sources other than CSID_GENERIC could then get
converted in convert_base_to_cs() based on an uninitialized use_nsecs field,
which usually results in -EINVAL during the following range check.

Pass in a fully zero initialized system_counterval_t to cure that.

Fixes: 6b2e299 ("timekeeping: Provide infrastructure for converting to/from a base clock")
Signed-off-by: Markus Blöchl <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: John Stultz <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/all/[email protected]

Author: Markus Blöchl

kernel/time/timekeeping.c

@@ -1256,7 +1256,7 @@ int get_device_system_crosststamp(int (*get_time_fn)
 				  struct system_time_snapshot *history_begin,
 				  struct system_device_crosststamp *xtstamp)
 {
-	struct system_counterval_t system_counterval;
+	struct system_counterval_t system_counterval = {};
 	struct timekeeper *tk = &tk_core.timekeeper;
 	u64 cycles, now, interval_start;
 	unsigned int clock_was_set_seq = 0;