timers: Preserve higher bits of expiration on index calculation

The higher bits of the timer expiration are cropped while calling
calc_index() due to the implicit cast from unsigned long to unsigned int.

This loss shouldn't have consequences on the current code since all the
computation to calculate the index is done on the lower 32 bits.

However to prepare for returning the actual bucket expiration from
calc_index() in order to properly fix base->next_expiry updates, the higher
bits need to be preserved.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200717140551.29076-3-frederic@kernel.org

kernel/time/timer.c

@@ -487,7 +487,7 @@ static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
  * Helper function to calculate the array index for a given expiry
  * time.
  */
-static inline unsigned calc_index(unsigned expires, unsigned lvl)
+static inline unsigned calc_index(unsigned long expires, unsigned lvl)
 {
 	expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
 	return LVL_OFFS(lvl) + (expires & LVL_MASK);