From c23e253e67c9d8a91a0ffa33c1f571a17f0a2403 Mon Sep 17 00:00:00 2001 From: Andreas Herrmann Date: Sat, 21 Feb 2009 00:16:35 +0100 Subject: [PATCH] x86: hpet: stop HPET_COUNTER when programming periodic mode Impact: fix system hang on some systems operating with HZ_1000 On a system that stalled with HZ_1000, the first value written to T0_CMP (when the main counter was not stopped) did not trigger an interrupt. Instead after the main counter wrapped around (after several minutes) an interrupt was triggered and afterwards the periodic interrupt took effect. This can be fixed by implementing HPET spec recommendation for programming the periodic mode (i.e. stopping the main counter). Signed-off-by: Andreas Herrmann Cc: Mark Hounschell Cc: Borislav Petkov Signed-off-by: Ingo Molnar --- arch/x86/kernel/hpet.c | 13 +++---------- 1 file changed, 3 insertions(+), 10 deletions(-) diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index 7ae1f1e8b9b7..648b3a2a3a44 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -309,29 +309,22 @@ static int hpet_setup_msi_irq(unsigned int irq); static void hpet_set_mode(enum clock_event_mode mode, struct clock_event_device *evt, int timer) { - unsigned long cfg, cmp, now; + unsigned long cfg; uint64_t delta; switch (mode) { case CLOCK_EVT_MODE_PERIODIC: + hpet_stop_counter(); delta = ((uint64_t)(NSEC_PER_SEC/HZ)) * evt->mult; delta >>= evt->shift; - now = hpet_readl(HPET_COUNTER); - cmp = now + (unsigned long) delta; cfg = hpet_readl(HPET_Tn_CFG(timer)); /* Make sure we use edge triggered interrupts */ cfg &= ~HPET_TN_LEVEL; cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL | HPET_TN_32BIT; hpet_writel(cfg, HPET_Tn_CFG(timer)); - /* - * The first write after writing TN_SETVAL to the - * config register sets the counter value, the second - * write sets the period. - */ - hpet_writel(cmp, HPET_Tn_CMP(timer)); - udelay(1); hpet_writel((unsigned long) delta, HPET_Tn_CMP(timer)); + hpet_start_counter(); hpet_print_config(); break; -- 2.39.5