Hi Mykola,
On 02/06/2025 10:04, Mykola Kvach wrote:
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From: Mirela Simonovic <mirela.simono...@aggios.com>
Timer interrupts must be disabled while the system is suspended to prevent
spurious wake-ups. Suspending the timers involves disabling both the EL1
physical timer and the EL2 hypervisor timer. Resuming consists of raising
the TIMER_SOFTIRQ, which prompts the generic timer code to reprogram the
EL2 timer as needed. Re-enabling of the EL1 timer is left to the entity
that uses it.
Introduce a new helper, disable_physical_timers, to encapsulate disabling
of the physical timers.
Signed-off-by: Mirela Simonovic <mirela.simono...@aggios.com>
Signed-off-by: Saeed Nowshadi <saeed.nowsh...@xilinx.com>
Signed-off-by: Mykola Kvach <mykola_kv...@epam.com>
---
Changes in V4:
- Rephrased comment and commit message for better clarity
- Created separate function for disabling physical timers
Changes in V3:
- time_suspend and time_resume are now conditionally compiled
under CONFIG_SYSTEM_SUSPEND
---
xen/arch/arm/include/asm/time.h | 5 +++++
xen/arch/arm/time.c | 38 +++++++++++++++++++++++++++------
2 files changed, 37 insertions(+), 6 deletions(-)
diff --git a/xen/arch/arm/include/asm/time.h b/xen/arch/arm/include/asm/time.h
index 49ad8c1a6d..f4fd0c6af5 100644
--- a/xen/arch/arm/include/asm/time.h
+++ b/xen/arch/arm/include/asm/time.h
@@ -108,6 +108,11 @@ void preinit_xen_time(void);
void force_update_vcpu_system_time(struct vcpu *v);
+#ifdef CONFIG_SYSTEM_SUSPEND
+void time_suspend(void);
+void time_resume(void);
+#endif /* CONFIG_SYSTEM_SUSPEND */
+
#endif /* __ARM_TIME_H__ */
/*
* Local variables:
diff --git a/xen/arch/arm/time.c b/xen/arch/arm/time.c
index e74d30d258..ad984fdfdd 100644
--- a/xen/arch/arm/time.c
+++ b/xen/arch/arm/time.c
@@ -303,6 +303,14 @@ static void check_timer_irq_cfg(unsigned int irq, const
char *which)
"WARNING: %s-timer IRQ%u is not level triggered.\n", which, irq);
}
+/* Disable physical timers for EL1 and EL2 on the current CPU */
+static inline void disable_physical_timers(void)
+{
+ WRITE_SYSREG(0, CNTP_CTL_EL0); /* Physical timer disabled */
+ WRITE_SYSREG(0, CNTHP_CTL_EL2); /* Hypervisor's timer disabled */
+ isb();
+}
+
/* Set up the timer interrupt on this CPU */
void init_timer_interrupt(void)
{
@@ -310,9 +318,7 @@ void init_timer_interrupt(void)
WRITE_SYSREG64(0, CNTVOFF_EL2); /* No VM-specific offset */
/* Do not let the VMs program the physical timer, only read the physical
counter */
WRITE_SYSREG(CNTHCTL_EL2_EL1PCTEN, CNTHCTL_EL2);
- WRITE_SYSREG(0, CNTP_CTL_EL0); /* Physical timer disabled */
- WRITE_SYSREG(0, CNTHP_CTL_EL2); /* Hypervisor's timer disabled */
- isb();
+ disable_physical_timers();
request_irq(timer_irq[TIMER_HYP_PPI], 0, htimer_interrupt,
"hyptimer", NULL);
@@ -330,9 +336,7 @@ void init_timer_interrupt(void)
*/
static void deinit_timer_interrupt(void)
{
- WRITE_SYSREG(0, CNTP_CTL_EL0); /* Disable physical timer */
- WRITE_SYSREG(0, CNTHP_CTL_EL2); /* Disable hypervisor's timer */
- isb();
+ disable_physical_timers();
release_irq(timer_irq[TIMER_HYP_PPI], NULL);
release_irq(timer_irq[TIMER_VIRT_PPI], NULL);
@@ -372,6 +376,28 @@ void domain_set_time_offset(struct domain *d, int64_t
time_offset_seconds)
/* XXX update guest visible wallclock time */
}
+#ifdef CONFIG_SYSTEM_SUSPEND
+
+void time_suspend(void)
+{
+ disable_physical_timers();
+}
+
+void time_resume(void)
+{
+ /*
+ * Raising the timer softirq triggers generic code to call reprogram_timer
+ * with the correct timeout (not known here).
+ *
+ * No further action is needed to restore timekeeping after power down,
+ * since the system counter is unaffected. See ARM DDI 0487 L.a, D12.1.2
+ * "The system counter must be implemented in an always-on power domain."
+ */
+ raise_softirq(TIMER_SOFTIRQ);
+}
+
+#endif /* CONFIG_SYSTEM_SUSPEND */
+
static int cpu_time_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
A question. Do you see CPU_DYING gets invoked during platform suspend ?
I wonder how this code path is invoked with
time_suspend()
- Ayan
--
2.48.1
