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author | Huacai Chen <chenhc@lemote.com> | 2016-07-21 14:27:51 +0800 |
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committer | Ralf Baechle <ralf@linux-mips.org> | 2016-07-24 12:01:00 +0200 |
commit | 3ef06653987d4c4536b408321edf0e5caa2a317f (patch) | |
tree | 2ceef19d66fd2d029e5b3b64454d947eac807383 /arch/mips | |
parent | 07d69579e7fec27e371296d8ca9d6076fc401b5c (diff) | |
download | linux-3ef06653987d4c4536b408321edf0e5caa2a317f.tar.gz linux-3ef06653987d4c4536b408321edf0e5caa2a317f.tar.bz2 linux-3ef06653987d4c4536b408321edf0e5caa2a317f.zip |
MIPS: hpet: Increase HPET_MIN_PROG_DELTA and decrease HPET_MIN_CYCLES
At first, we prefer to use mips clockevent device, so we decrease the
rating of hpet clockevent device.
For hpet, if HPET_MIN_PROG_DELTA (minimum delta of hpet programming) is
too small and HPET_MIN_CYCLES (threshold of -ETIME checking) is too
large, then hpet_next_event() can easily return -ETIME. After commit
c6eb3f70d44828 ("hrtimer: Get rid of hrtimer softirq") this will cause
a RCU stall.
So, HPET_MIN_PROG_DELTA must be sufficient that we don't re-trip the
-ETIME check -- if we do, we will return -ETIME, forward the next event
time, try to set it, return -ETIME again, and basically lock the system
up. Meanwhile, HPET_MIN_CYCLES doesn't need to be too large, 16 cycles
is enough.
This solution is similar to commit f9eccf24615672 ("clocksource/drivers
/vt8500: Increase the minimum delta").
By the way, this patch ensures hpet count/compare to be 32-bit long.
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Cc: John Crispin <john@phrozen.org>
Cc: Steven J . Hill <Steven.Hill@imgtec.com>
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13819/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips')
-rw-r--r-- | arch/mips/loongson64/loongson-3/hpet.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/arch/mips/loongson64/loongson-3/hpet.c b/arch/mips/loongson64/loongson-3/hpet.c index 249039af66c4..4788bea62a6a 100644 --- a/arch/mips/loongson64/loongson-3/hpet.c +++ b/arch/mips/loongson64/loongson-3/hpet.c @@ -13,8 +13,8 @@ #define SMBUS_PCI_REG64 0x64 #define SMBUS_PCI_REGB4 0xb4 -#define HPET_MIN_CYCLES 64 -#define HPET_MIN_PROG_DELTA (HPET_MIN_CYCLES + (HPET_MIN_CYCLES >> 1)) +#define HPET_MIN_CYCLES 16 +#define HPET_MIN_PROG_DELTA (HPET_MIN_CYCLES * 12) static DEFINE_SPINLOCK(hpet_lock); DEFINE_PER_CPU(struct clock_event_device, hpet_clockevent_device); @@ -157,14 +157,14 @@ static int hpet_tick_resume(struct clock_event_device *evt) static int hpet_next_event(unsigned long delta, struct clock_event_device *evt) { - unsigned int cnt; - int res; + u32 cnt; + s32 res; cnt = hpet_read(HPET_COUNTER); - cnt += delta; + cnt += (u32) delta; hpet_write(HPET_T0_CMP, cnt); - res = (int)(cnt - hpet_read(HPET_COUNTER)); + res = (s32)(cnt - hpet_read(HPET_COUNTER)); return res < HPET_MIN_CYCLES ? -ETIME : 0; } @@ -230,7 +230,7 @@ void __init setup_hpet_timer(void) cd = &per_cpu(hpet_clockevent_device, cpu); cd->name = "hpet"; - cd->rating = 320; + cd->rating = 100; cd->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT; cd->set_state_shutdown = hpet_set_state_shutdown; cd->set_state_periodic = hpet_set_state_periodic; |