Extent the current suspend/resume implementation to include support for

parking CPUs in a WFE/WFI loop.

ok deraadt@, mlarkin@

diff --git a/sys/arch/arm64/arm64/cpu.c b/sys/arch/arm64/arm64/cpu.c
index bb8e82e..04dde3f 100644 (file)
--- a/sys/arch/arm64/arm64/cpu.c
+++ b/sys/arch/arm64/arm64/cpu.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: cpu.c,v 1.71 2022/10/04 19:41:21 kettenis Exp $       */
+/*     $OpenBSD: cpu.c,v 1.72 2022/11/08 16:53:40 kettenis Exp $       */
 
 /*
  * Copyright (c) 2016 Dale Rahn <drahn@dalerahn.com>
@@ -935,18 +935,47 @@ void
 cpu_halt(void)
 {
        struct cpu_info *ci = curcpu();
+       int count = 0;
 
        KERNEL_ASSERT_UNLOCKED();
        SCHED_ASSERT_UNLOCKED();
 
        intr_disable();
-       ci->ci_flags &= ~CPUF_RUNNING;
+
+       atomic_clearbits_int(&ci->ci_flags,
+           CPUF_RUNNING | CPUF_PRESENT | CPUF_GO);
+
 #if NPSCI > 0
        psci_cpu_off();
 #endif
-       for (;;)
-               __asm volatile("wfi");
-       /* NOTREACHED */
+
+       /*
+        * If we failed to turn ourselves off using PSCI, declare that
+        * we're still present and spin in a low power state until
+        * we're told to wake up again by the primary CPU.
+        */
+
+       atomic_setbits_int(&ci->ci_flags, CPUF_PRESENT);
+
+       /* Mask clock interrupts. */
+       WRITE_SPECIALREG(cntv_ctl_el0,
+           READ_SPECIALREG(cntv_ctl_el0) | CNTV_CTL_IMASK);
+
+       while ((ci->ci_flags & CPUF_GO) == 0) {
+               __asm volatile("wfe");
+               count++;
+       }
+
+       atomic_setbits_int(&ci->ci_flags, CPUF_RUNNING);
+       __asm volatile("dsb sy; sev" ::: "memory");
+
+       intr_enable();
+
+       /* Unmask clock interrupts. */
+       WRITE_SPECIALREG(cntv_ctl_el0,
+           READ_SPECIALREG(cntv_ctl_el0) & ~CNTV_CTL_IMASK);
+
+       printf("%s: %d wakeup events\n", ci->ci_dev->dv_xname, count);
 }
 
 void
@@ -997,6 +1026,48 @@ cpu_suspend_primary(void)
        paddr_t startaddr, data;
        uint64_t ttbr1;
 
+       if (!psci_can_suspend()) {
+               int count = 0;
+
+               /*
+                * If PSCI doesn't support SYSTEM_SUSPEND, spin in a
+                * low power state waiting for an interrupt that wakes
+                * us up again.
+                */
+
+               /* Mask clock interrupts. */
+               WRITE_SPECIALREG(cntv_ctl_el0,
+                   READ_SPECIALREG(cntv_ctl_el0) | CNTV_CTL_IMASK);
+
+               /*
+                * All non-wakeup interrupts should be masked at this
+                * point; re-enable interrupts such that wakeup
+                * interrupts actually wake us up.  Set a flag such
+                * that drivers can tell we're suspended and change
+                * their behaviour accordingly.  They can wake us up
+                * by clearing the flag.
+                */
+               cpu_suspended = 1;
+               arm_intr_func.setipl(IPL_NONE);
+               intr_enable();
+
+               while (cpu_suspended) {
+                       __asm volatile("wfi");
+                       count++;
+               }
+
+               intr_disable();
+               arm_intr_func.setipl(IPL_HIGH);
+
+               /* Unmask clock interrupts. */
+               WRITE_SPECIALREG(cntv_ctl_el0,
+                   READ_SPECIALREG(cntv_ctl_el0) & ~CNTV_CTL_IMASK);
+
+               printf("%s: %d wakeup events\n", ci->ci_dev->dv_xname, count);
+
+               return 0;
+       }
+
        cpu_suspended = 0;
        setjmp(&cpu_suspend_jmpbuf);
        if (cpu_suspended) {
@@ -1033,13 +1104,15 @@ cpu_resume_secondary(struct cpu_info *ci)
        struct switchframe *sf;
        int timeout = 10000;
 
+       if (ci->ci_flags & CPUF_PRESENT)
+               return;
+
        ci->ci_curproc = NULL;
        ci->ci_curpcb = NULL;
        ci->ci_curpm = NULL;
        ci->ci_cpl = IPL_NONE;
        ci->ci_ipending = 0;
        ci->ci_idepth = 0;
-       ci->ci_flags &= ~CPUF_PRESENT;
 
 #ifdef DIAGNOSTIC
        ci->ci_mutex_level = 0;