The system initially uses a jiffy-based sched clock. When the platform
registers a new timer for sched_clock, sched_clock can jump backwards.
Once sched_clock_postinit() runs it should be safe to rely on it.
Also sched_clock_cpu() relies on completion of sched_clock_init()
and until that happens sched_clock_cpu() returns zero. This is used
in the irq accounting path which window-based stats relies upon.
So do not set window_start until sched_clock_cpu() is working.
Change-Id: Ided349de8f8554f80a027ace0f63ea52b1c38c68
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
During suspend we call sched_clock_poll() to update the epoch and
accumulated time and reprogram the sched_clock_timer to fire
before the next wrap-around time. Unfortunately,
sched_clock_poll() doesn't restart the timer, instead it relies
on the hrtimer layer to do that and during suspend we aren't
calling that function from the hrtimer layer. Instead, we're
reprogramming the expires time while the hrtimer is enqueued,
which can cause the hrtimer tree to be corrupted. Furthermore, we
restart the timer during suspend but we update the epoch during
resume which seems counter-intuitive.
Let's fix this by saving the accumulated state and canceling the
timer during suspend. On resume we can update the epoch and
restart the timer similar to what we would do if we were starting
the clock for the first time.
Change-Id: Iee2a1cca42e5b681347ea0607e9af420a63892d7
CRs-Fixed: 696826
Fixes: a08ca5d1089d "sched_clock: Use an hrtimer instead of timer"
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
The ARM architected system counter has at least 56 usable bits.
Add support for counters with more than 32 bits to the generic
sched_clock implementation so we can increase the time between
wakeups due to dealing with wrap-around on these devices while
benefiting from the irqtime accounting and suspend/resume
handling that the generic sched_clock code already has. On my
system using 56 bits over 32 bits changes the wraparound time
from a few minutes to an hour. For faster running counters (GHz
range) this is even more important because we may not be able to
execute the timer in time to deal with the wraparound if only 32
bits are used.
We choose a maxsec value of 3600 seconds because we assume no
system will go idle for more than an hour. In the future we may
need to increase this value.
Note: All users should switch over to the 64-bit read function so
we can remove setup_sched_clock() in favor of sched_clock_register().
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Git-commit: e7e3ff1bfe9c42ee31172e9afdc0383a9e595e29
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ian Maund <imaund@codeaurora.org>
In the next patch we're going to increase the number of bits that
the generic sched_clock can handle to be greater than 32. With
more than 32 bits the wraparound time can be larger than what can
fit into the units that msecs_to_jiffies takes (unsigned int).
Luckily, the wraparound is initially calculated in nanoseconds
which we can easily use with hrtimers, so switch to using an
hrtimer.
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
[jstultz: Fixup hrtimer intitialization order issue]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Git-commit: a08ca5d1089da03724f96fa0870c64968e66765b
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ian Maund <imaund@codeaurora.org>
We're going to increase the cyc value to 64 bits in the near
future. Doing that is going to break the custom seqcount
implementation in the sched_clock code because 64 bit numbers
aren't guaranteed to be atomic. Replace the cyc_copy with a
seqcount to avoid this problem.
Cc: Russell King <linux@arm.linux.org.uk>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Git-commit: 85c3d2dd15be4d577a37ffb8bbbd019fc8e3280a
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[imaund@codeaurora.org: resolve merge conflicts]
Signed-off-by: Ian Maund <imaund@codeaurora.org>
There is a small race between when the cycle count is read from
the hardware and when the epoch stabilizes. Consider this
scenario:
CPU0 CPU1
---- ----
cyc = read_sched_clock()
cyc_to_sched_clock()
update_sched_clock()
...
cd.epoch_cyc = cyc;
epoch_cyc = cd.epoch_cyc;
...
epoch_ns + cyc_to_ns((cyc - epoch_cyc)
The cyc on cpu0 was read before the epoch changed. But we
calculate the nanoseconds based on the new epoch by subtracting
the new epoch from the old cycle count. Since epoch is most likely
larger than the old cycle count we calculate a large number that
will be converted to nanoseconds and added to epoch_ns, causing
time to jump forward too much.
Fix this problem by reading the hardware after the epoch has
stabilized.
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Git-commit: 336ae1180df5f69b9e0fb6561bec01c5f64361cf
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Ian Maund <imaund@codeaurora.org>
Nothing about the sched_clock implementation in the ARM port is
specific to the architecture. Generalize the code so that other
architectures can use it by selecting GENERIC_SCHED_CLOCK.
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
[jstultz: Merge minor collisions with other patches in my tree]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Git-commit: 38ff87f77af0b5a93fc8581cff1d6e5692ab8970
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[imaund@codeaurora.org: resolve merge conflicts]
Signed-off-by: Ian Maund <imaund@codeaurora.org>
2014-02-07 15:55:53 -08:00
Renamed from arch/arm/kernel/sched_clock.c (Browse further)
LuK1337
Steve Muckle
Stephen Boyd