vdso: Consolidate vdso_calc_delta()

Consolidate vdso_calc_delta(), in preparation for further simplification.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240325064023.2997-2-adrian.hunter@intel.com

Author: ahunter6

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

@@ -13,6 +13,17 @@
 
 #define VDSO_HAS_TIME			1
 
+/*
+ * powerpc specific delta calculation.
+ *
+ * This variant removes the masking of the subtraction because the
+ * clocksource mask of all VDSO capable clocksources on powerpc is U64_MAX
+ * which would result in a pointless operation. The compiler cannot
+ * optimize it away as the mask comes from the vdso data and is not compile
+ * time constant.
+ */
+#define VDSO_DELTA_NOMASK		1
+
 static __always_inline int do_syscall_2(const unsigned long _r0, const unsigned long _r3,
 					const unsigned long _r4)
 {
@@ -104,21 +115,6 @@ static inline bool vdso_clocksource_ok(const struct vdso_data *vd)
 }
 #define vdso_clocksource_ok vdso_clocksource_ok
 
-/*
- * powerpc specific delta calculation.
- *
- * This variant removes the masking of the subtraction because the
- * clocksource mask of all VDSO capable clocksources on powerpc is U64_MAX
- * which would result in a pointless operation. The compiler cannot
- * optimize it away as the mask comes from the vdso data and is not compile
- * time constant.
- */
-static __always_inline u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
-{
-	return (cycles - last) * mult;
-}
-#define vdso_calc_delta vdso_calc_delta
-
 #ifndef __powerpc64__
 static __always_inline u64 vdso_shift_ns(u64 ns, unsigned long shift)
 {

arch/s390/include/asm/vdso/gettimeofday.h

@@ -6,16 +6,13 @@
 
 #define VDSO_HAS_CLOCK_GETRES 1
 
+#define VDSO_DELTA_NOMASK 1
+
 #include <asm/syscall.h>
 #include <asm/timex.h>
 #include <asm/unistd.h>
 #include <linux/compiler.h>
 
-#define vdso_calc_delta __arch_vdso_calc_delta
-static __always_inline u64 __arch_vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
-{
-	return (cycles - last) * mult;
-}
 
 static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
 {

lib/vdso/gettimeofday.c

@@ -6,14 +6,21 @@
 #include <vdso/helpers.h>
 
 #ifndef vdso_calc_delta
+
+#ifdef VDSO_DELTA_NOMASK
+# define VDSO_DELTA_MASK(mask)	U64_MAX
+#else
+# define VDSO_DELTA_MASK(mask)	(mask)
+#endif
+
 /*
  * Default implementation which works for all sane clocksources. That
  * obviously excludes x86/TSC.
  */
 static __always_inline
 u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
 {
-	return ((cycles - last) & mask) * mult;
+	return ((cycles - last) & VDSO_DELTA_MASK(mask)) * mult;
 }
 #endif