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| author | Colin Cross <ccross@android.com> | 2012-08-07 19:05:10 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2012-08-11 09:15:58 +0100 |
| commit | 237ec6f2e51d2fc2ff37c7c5f1ccc9264d09c85b (patch) | |
| tree | 17a21e6c00129a703d906166f0e640089e3af6b7 /arch | |
| parent | f1898f6be9a2e3690fb62d8307849b86a89cc36c (diff) | |
| download | linux-237ec6f2e51d2fc2ff37c7c5f1ccc9264d09c85b.tar.gz linux-237ec6f2e51d2fc2ff37c7c5f1ccc9264d09c85b.tar.bz2 linux-237ec6f2e51d2fc2ff37c7c5f1ccc9264d09c85b.zip | |
ARM: 7486/1: sched_clock: update epoch_cyc on resume
Many clocks that are used to provide sched_clock will reset during
suspend. If read_sched_clock returns 0 after suspend, sched_clock will
appear to jump forward. This patch resets cd.epoch_cyc to the current
value of read_sched_clock during resume, which causes sched_clock() just
after suspend to return the same value as sched_clock() just before
suspend.
In addition, during the window where epoch_ns has been updated before
suspend, but epoch_cyc has not been updated after suspend, it is unknown
whether the clock has reset or not, and sched_clock() could return a
bogus value. Add a suspended flag, and return the pre-suspend epoch_ns
value during this period.
The new behavior is triggered by calling setup_sched_clock_needs_suspend
instead of setup_sched_clock.
Signed-off-by: Colin Cross <ccross@android.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/include/asm/sched_clock.h | 2 | ||||
| -rw-r--r-- | arch/arm/kernel/sched_clock.c | 24 |
2 files changed, 26 insertions, 0 deletions
diff --git a/arch/arm/include/asm/sched_clock.h b/arch/arm/include/asm/sched_clock.h index e3f757263438..05b8e82ec9f5 100644 --- a/arch/arm/include/asm/sched_clock.h +++ b/arch/arm/include/asm/sched_clock.h @@ -10,5 +10,7 @@ extern void sched_clock_postinit(void); extern void setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate); +extern void setup_sched_clock_needs_suspend(u32 (*read)(void), int bits, + unsigned long rate); #endif diff --git a/arch/arm/kernel/sched_clock.c b/arch/arm/kernel/sched_clock.c index 27d186abbc06..f4515393248d 100644 --- a/arch/arm/kernel/sched_clock.c +++ b/arch/arm/kernel/sched_clock.c @@ -21,6 +21,8 @@ struct clock_data { u32 epoch_cyc_copy; u32 mult; u32 shift; + bool suspended; + bool needs_suspend; }; static void sched_clock_poll(unsigned long wrap_ticks); @@ -49,6 +51,9 @@ static unsigned long long cyc_to_sched_clock(u32 cyc, u32 mask) u64 epoch_ns; u32 epoch_cyc; + if (cd.suspended) + return cd.epoch_ns; + /* * Load the epoch_cyc and epoch_ns atomically. We do this by * ensuring that we always write epoch_cyc, epoch_ns and @@ -98,6 +103,13 @@ static void sched_clock_poll(unsigned long wrap_ticks) update_sched_clock(); } +void __init setup_sched_clock_needs_suspend(u32 (*read)(void), int bits, + unsigned long rate) +{ + setup_sched_clock(read, bits, rate); + cd.needs_suspend = true; +} + void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate) { unsigned long r, w; @@ -169,11 +181,23 @@ void __init sched_clock_postinit(void) static int sched_clock_suspend(void) { sched_clock_poll(sched_clock_timer.data); + if (cd.needs_suspend) + cd.suspended = true; return 0; } +static void sched_clock_resume(void) +{ + if (cd.needs_suspend) { + cd.epoch_cyc = read_sched_clock(); + cd.epoch_cyc_copy = cd.epoch_cyc; + cd.suspended = false; + } +} + static struct syscore_ops sched_clock_ops = { .suspend = sched_clock_suspend, + .resume = sched_clock_resume, }; static int __init sched_clock_syscore_init(void) |