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.
Unified · Split
| @@ -115,6 +115,12 @@ static inline bool timespec_valid_strict(const struct timespec *ts) · 114 unmodified lines | |||
| 115 | return true; | 115 | return true; |
| 116 | } | 116 | } |
| 117 | 117 | ||
| 118 | extern bool persistent_clock_exist; | ||
| 119 | static inline bool has_persistent_clock(void) | ||
| 120 | { | ||
| 121 | return persistent_clock_exist; | ||
| 122 | } | ||
| 123 | |||
| 118 | extern void read_persistent_clock(struct timespec *ts); | 124 | extern void read_persistent_clock(struct timespec *ts); |
| 119 | extern void read_boot_clock(struct timespec *ts); | 125 | extern void read_boot_clock(struct timespec *ts); |
| 120 | extern int update_persistent_clock(struct timespec now); | 126 | extern int update_persistent_clock(struct timespec now); |
| @@ -28,6 +28,9 @@ static struct timekeeper timekeeper; · 27 unmodified lines | |||
| 28 | /* flag for if timekeeping is suspended */ | 28 | /* flag for if timekeeping is suspended */ |
| 29 | int __read_mostly timekeeping_suspended; | 29 | int __read_mostly timekeeping_suspended; |
| 30 | 30 | ||
| 31 | /* Flag for if there is a persistent clock on this platform */ | ||
| 32 | bool __read_mostly persistent_clock_exist = false; | ||
| 33 | |||
| 31 | static inline void tk_normalize_xtime(struct timekeeper *tk) | 34 | static inline void tk_normalize_xtime(struct timekeeper *tk) |
| 32 | { | 35 | { |
| 33 | while (tk->xtime_nsec >= ((u64)NSEC_PER_SEC << tk->shift)) { | 36 | while (tk->xtime_nsec >= ((u64)NSEC_PER_SEC << tk->shift)) { |
| @@ -609,12 +612,14 @@ void __init timekeeping_init(void) · 575 unmodified lines | |||
| 609 | struct timespec now, boot, tmp; | 612 | struct timespec now, boot, tmp; |
| 610 | 613 | ||
| 611 | read_persistent_clock(&now); | 614 | read_persistent_clock(&now); |
| 615 | |||
| 612 | if (!timespec_valid_strict(&now)) { | 616 | if (!timespec_valid_strict(&now)) { |
| 613 | pr_warn("WARNING: Persistent clock returned invalid value!\n" | 617 | pr_warn("WARNING: Persistent clock returned invalid value!\n" |
| 614 | " Check your CMOS/BIOS settings.\n"); | 618 | " Check your CMOS/BIOS settings.\n"); |
| 615 | now.tv_sec = 0; | 619 | now.tv_sec = 0; |
| 616 | now.tv_nsec = 0; | 620 | now.tv_nsec = 0; |
| 617 | } | 621 | } else if (now.tv_sec || now.tv_nsec) |
| 622 | persistent_clock_exist = true; | ||
| 618 | 623 | ||
| 619 | read_boot_clock(&boot); | 624 | read_boot_clock(&boot); |
| 620 | if (!timespec_valid_strict(&boot)) { | 625 | if (!timespec_valid_strict(&boot)) { |
| @@ -687,11 +692,12 @@ void timekeeping_inject_sleeptime(struct timespec *delta) · 66 unmodified lines | |||
| 687 | { | 692 | { |
| 688 | struct timekeeper *tk = &timekeeper; | 693 | struct timekeeper *tk = &timekeeper; |
| 689 | unsigned long flags; | 694 | unsigned long flags; |
| 690 | struct timespec ts; | ||
| 691 | 695 | ||
| 692 | /* Make sure we don't set the clock twice */ | 696 | /* |
| 693 | read_persistent_clock(&ts); | 697 | * Make sure we don't set the clock twice, as timekeeping_resume() |
| 694 | if (!(ts.tv_sec == 0 && ts.tv_nsec == 0)) | 698 | * already did it |
| 699 | */ | ||
| 700 | if (has_persistent_clock()) | ||
| 695 | return; | 701 | return; |
| 696 | 702 | ||
| 697 | write_seqlock_irqsave(&tk->lock, flags); | 703 | write_seqlock_irqsave(&tk->lock, flags); |