x86/vdso: Prepare introduction of struct vdso_clock

To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.

To prepare for the rework of the data structures, replace the struct
vdso_time_data pointer with a struct vdso_clock pointer where applicable.

No functional change.

Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-15-c1b5c69a166f@linutronix.de

arch/x86/include/asm/vdso/gettimeofday.h

@@ -261,7 +261,7 @@ static inline u64 __arch_get_hw_counter(s32 clock_mode,
 	return U64_MAX;
 }
 
-static inline bool arch_vdso_clocksource_ok(const struct vdso_time_data *vd)
+static inline bool arch_vdso_clocksource_ok(const struct vdso_clock *vc)
 {
 	return true;
 }
@@ -300,34 +300,34 @@ static inline bool arch_vdso_cycles_ok(u64 cycles)
  * declares everything with the MSB/Sign-bit set as invalid. Therefore the
  * effective mask is S64_MAX.
  */
-static __always_inline u64 vdso_calc_ns(const struct vdso_time_data *vd, u64 cycles, u64 base)
+static __always_inline u64 vdso_calc_ns(const struct vdso_clock *vc, u64 cycles, u64 base)
 {
-	u64 delta = cycles - vd->cycle_last;
+	u64 delta = cycles - vc->cycle_last;
 
 	/*
 	 * Negative motion and deltas which can cause multiplication
 	 * overflow require special treatment. This check covers both as
-	 * negative motion is guaranteed to be greater than @vd::max_cycles
+	 * negative motion is guaranteed to be greater than @vc::max_cycles
 	 * due to unsigned comparison.
 	 *
 	 * Due to the MSB/Sign-bit being used as invalid marker (see
 	 * arch_vdso_cycles_ok() above), the effective mask is S64_MAX, but that
 	 * case is also unlikely and will also take the unlikely path here.
 	 */
-	if (unlikely(delta > vd->max_cycles)) {
+	if (unlikely(delta > vc->max_cycles)) {
 		/*
 		 * Due to the above mentioned TSC wobbles, filter out
 		 * negative motion.  Per the above masking, the effective
 		 * sign bit is now bit 62.
 		 */
 		if (delta & (1ULL << 62))
-			return base >> vd->shift;
+			return base >> vc->shift;
 
 		/* Handle multiplication overflow gracefully */
-		return mul_u64_u32_add_u64_shr(delta & S64_MAX, vd->mult, base, vd->shift);
+		return mul_u64_u32_add_u64_shr(delta & S64_MAX, vc->mult, base, vc->shift);
 	}
 
-	return ((delta * vd->mult) + base) >> vd->shift;
+	return ((delta * vc->mult) + base) >> vc->shift;
 }
 #define vdso_calc_ns vdso_calc_ns