diff mbox series

[09/16] xen/arm: add suspend and resume timer helpers

Message ID 1c84532d015797f23172598a820223b6fa8bcb8d.1741164138.git.xakep.amatop@gmail.com (mailing list archive)
State New
Headers show
Series Suspend to RAM support for Xen on arm64 | expand

Commit Message

Mykola Kvach March 5, 2025, 9:11 a.m. UTC 
From: Mirela Simonovic <mirela.simonovic@aggios.com>

Timer interrupts have to be disabled while the system is in suspend.
Otherwise, a timer interrupt would fire and wake-up the system.
Suspending the timer interrupts consists of disabling physical EL1
and EL2 timers. The resume consists only of raising timer softirq,
which will trigger the generic timer code to reprogram the EL2 timer
as needed. Enabling of EL1 physical timer will be triggered by an
entity which uses it.

Signed-off-by: Mirela Simonovic <mirela.simonovic@aggios.com>
Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xilinx.com>
Signed-off-by: Mykola Kvach <mykola_kvach@epam.com>
---
 xen/arch/arm/include/asm/time.h |  5 +++++
 xen/arch/arm/time.c             | 26 ++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)
diff mbox series

Patch

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..89c5773244 100644
--- a/xen/arch/arm/time.c
+++ b/xen/arch/arm/time.c
@@ -372,6 +372,32 @@  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 EL1 timer */
+    WRITE_SYSREG(0, CNTP_CTL_EL0);
+
+    /* Disable hypervisor's timer */
+    WRITE_SYSREG(0, CNTHP_CTL_EL2);
+    isb();
+}
+
+void time_resume(void)
+{
+    /*
+     * Raising timer softirq will trigger generic timer code to reprogram_timer
+     * with the correct timeout value (which is not known here). There is no
+     * need to do anything else in order to recover the time keeping from power
+     * down, because the system counter is not affected by the power down (it
+     * resides out of the ARM's cluster in an always-on part of the SoC).
+     */
+    raise_softirq(TIMER_SOFTIRQ);
+}
+
+#endif /* CONFIG_SYSTEM_SUSPEND */
+
 static int cpu_time_callback(struct notifier_block *nfb,
                              unsigned long action,
                              void *hcpu)