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authorHuacai Chen <chenhc@lemote.com>2016-07-21 14:27:51 +0800
committerRalf Baechle <ralf@linux-mips.org>2016-07-24 12:01:00 +0200
commit3ef06653987d4c4536b408321edf0e5caa2a317f (patch)
tree2ceef19d66fd2d029e5b3b64454d947eac807383 /arch/mips/loongson64
parent07d69579e7fec27e371296d8ca9d6076fc401b5c (diff)
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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/loongson64')
-rw-r--r--arch/mips/loongson64/loongson-3/hpet.c14
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;