[PATCH V2 1/2] rtc/hpet: Factorize hpet_rtc_timer_init()

From: Pratyush Anand
Date: Tue Aug 02 2016 - 03:29:05 EST


We have observed on few machines with rtc-cmos device that
hpet_rtc_interrupt() is called before cmos_do_probe() could call
hpet_rtc_timer_init(). It has not been observed during normal boot/reboot
of machines. It *sometime* happens when system is booted with kdump
secondary kernel. So, neither hpet_default_delta nor hpet_t1_cmp is
initialized by the time interrupt is raised in the given situation.
Therefore while loop of hpet_cnt_ahead() in hpet_rtc_timer_reinit() never
completes. This leads to "NMI watchdog: Watchdog detected hard LOCKUP on
cpu 0".

This patch factorize hpet_rtc_timer_init(), so that counter can be
initialized before irq is registered.

No functional change in this patch.

Signed-off-by: Pratyush Anand <panand@xxxxxxxxxx>
---
arch/x86/include/asm/hpet.h | 2 ++
arch/x86/kernel/hpet.c | 41 +++++++++++++++++++++++++++++++++++------
2 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/hpet.h b/arch/x86/include/asm/hpet.h
index cc285ec4b2c1..8eecb31bebcb 100644
--- a/arch/x86/include/asm/hpet.h
+++ b/arch/x86/include/asm/hpet.h
@@ -96,6 +96,8 @@ extern int hpet_set_alarm_time(unsigned char hrs, unsigned char min,
unsigned char sec);
extern int hpet_set_periodic_freq(unsigned long freq);
extern int hpet_rtc_dropped_irq(void);
+extern int hpet_rtc_timer_counter_init(void);
+extern int hpet_rtc_timer_enable(void);
extern int hpet_rtc_timer_init(void);
extern irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id);
extern int hpet_register_irq_handler(rtc_irq_handler handler);
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 3d747070fe67..c9da694ff236 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -1075,14 +1075,12 @@ void hpet_unregister_irq_handler(rtc_irq_handler handler)
EXPORT_SYMBOL_GPL(hpet_unregister_irq_handler);

/*
- * Timer 1 for RTC emulation. We use one shot mode, as periodic mode
- * is not supported by all HPET implementations for timer 1.
- *
- * hpet_rtc_timer_init() is called when the rtc is initialized.
+ * hpet_rtc_timer_counter_init() is called before interrupt can be
+ * registered
*/
-int hpet_rtc_timer_init(void)
+int hpet_rtc_timer_counter_init(void)
{
- unsigned int cfg, cnt, delta;
+ unsigned int cnt, delta;
unsigned long flags;

if (!is_hpet_enabled())
@@ -1107,6 +1105,22 @@ int hpet_rtc_timer_init(void)
hpet_writel(cnt, HPET_T1_CMP);
hpet_t1_cmp = cnt;

+ local_irq_restore(flags);
+
+ return 1;
+}
+EXPORT_SYMBOL_GPL(hpet_rtc_timer_counter_init);
+
+/*
+ * hpet_rtc_timer_enable() is called during RTC initialization
+ */
+int hpet_rtc_timer_enable(void)
+{
+ unsigned int cfg;
+ unsigned long flags;
+
+ local_irq_save(flags);
+
cfg = hpet_readl(HPET_T1_CFG);
cfg &= ~HPET_TN_PERIODIC;
cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
@@ -1116,6 +1130,21 @@ int hpet_rtc_timer_init(void)

return 1;
}
+EXPORT_SYMBOL_GPL(hpet_rtc_timer_enable);
+
+/*
+ * Timer 1 for RTC emulation. We use one shot mode, as periodic mode
+ * is not supported by all HPET implementations for timer 1.
+ *
+ * hpet_rtc_timer_init() is called when the rtc is initialized.
+ */
+int hpet_rtc_timer_init(void)
+{
+ if (!hpet_rtc_timer_counter_init())
+ return 0;
+
+ return hpet_rtc_timer_enable();
+}
EXPORT_SYMBOL_GPL(hpet_rtc_timer_init);

static void hpet_disable_rtc_channel(void)
--
2.5.5