all platforms: separate cpu_initclocks() from cpu_startclock()

To give the primary CPU an opportunity to perform clock interrupt
preparation in a machine-independent manner we need to separate the
"initialization" parts of cpu_initclocks() from the "start the clock
interrupt" parts.  Currently, cpu_initclocks() does everything all at
once, so there is no space for this MI setup.

Many platforms have more-or-less already done this separation by
implementing a separate routine named "cpu_startclock()".  This patch
promotes cpu_startclock() from de facto standard to mandatory API.

- Prototype cpu_startclock() in sys/systm.h alongside cpu_initclocks().
  The separation of responsibility between the two routines is a bit
  fuzzy but the basic guidelines are as follows:

  + cpu_initclocks() must initialize hz, stathz, and profhz, and call
    clockintr_init().

  + cpu_startclock() must call clockintr_cpu_init() and start the clock
    interrupt cycle on the calling CPU.

  These guidelines will shift in the future, but that's the way things
  stand as of *this* commit.

- In initclocks(): first call cpu_initclocks(), then do MI setup, and
  last call cpu_startclock().

- On platforms where cpu_startclock() already exists: don't call
  cpu_startclock() from cpu_initclocks() anymore.

- On platforms where cpu_startclock() doesn't yet exist: implement it.
  Usually this is as simple as dividing cpu_initclocks() in two.

Tested on amd64 (i8254, lapic), arm64, i386 (i8254, lapic), macppc,
mips64/octeon, and sparc64.  Tested on arm/armv7 (agtimer(4)) by
phessler@ and jmatthew@.  Tested on m88k/luna88k by aoyama@.  Tested
on powerpc64 by gkoehler@ and mlarkin@.  Tested on riscv64 by
jmatthew@.

Thread: https://marc.info/?l=openbsd-tech&m=169195251322149&w=2

3 files changed, 3 insertions, 20 deletions

diff --git a/sys/arch/arm/cortex/agtimer.c b/sys/arch/arm/cortex/agtimer.c
index 13b0af6f8e1..88e201abe8a 100644
--- a/sys/arch/arm/cortex/agtimer.c
+++ b/sys/arch/arm/cortex/agtimer.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: agtimer.c,v 1.18 2023/07/25 18:16:19 cheloha Exp $ */
+/* $OpenBSD: agtimer.c,v 1.19 2023/08/23 01:55:46 cheloha Exp $ */
 /*
  * Copyright (c) 2011 Dale Rahn <drahn@openbsd.org>
  * Copyright (c) 2013 Patrick Wildt <patrick@blueri.se>
@@ -227,7 +227,6 @@ void
 agtimer_cpu_initclocks(void)
 {
 	struct agtimer_softc	*sc = agtimer_cd.cd_devs[0];
-	uint32_t		 reg;
 
 	stathz = hz;
 	profhz = stathz * 10;
@@ -237,21 +236,11 @@ agtimer_cpu_initclocks(void)
 		agtimer_set_clockrate(agtimer_frequency);
 	}
 
-	clockintr_cpu_init(&agtimer_intrclock);
-
 	/* Setup secure and non-secure timer IRQs. */
 	arm_intr_establish_fdt_idx(sc->sc_node, 0, IPL_CLOCK,
 	    agtimer_intr, NULL, "tick");
 	arm_intr_establish_fdt_idx(sc->sc_node, 1, IPL_CLOCK,
 	    agtimer_intr, NULL, "tick");
-
-	reg = agtimer_get_ctrl();
-	reg &= ~GTIMER_CNTP_CTL_IMASK;
-	reg |= GTIMER_CNTP_CTL_ENABLE;
-	agtimer_set_tval(INT32_MAX);
-	agtimer_set_ctrl(reg);
-
-	clockintr_trigger();
 }
 
 void
diff --git a/sys/arch/arm/cortex/amptimer.c b/sys/arch/arm/cortex/amptimer.c
index 6fcf495791c..299f9fe8c61 100644
--- a/sys/arch/arm/cortex/amptimer.c
+++ b/sys/arch/arm/cortex/amptimer.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: amptimer.c,v 1.17 2023/07/25 18:16:19 cheloha Exp $ */
+/* $OpenBSD: amptimer.c,v 1.18 2023/08/23 01:55:46 cheloha Exp $ */
 /*
  * Copyright (c) 2011 Dale Rahn <drahn@openbsd.org>
  *
@@ -301,10 +301,6 @@ amptimer_cpu_initclocks(void)
 	/* Enable private timer counter and interrupt. */
 	bus_space_write_4(sc->sc_iot, sc->sc_pioh, PTIMER_CTRL,
 	    (PTIMER_CTRL_ENABLE | PTIMER_CTRL_IRQEN));
-
-	/* Start the clock interrupt cycle. */
-	clockintr_cpu_init(&amptimer_intrclock);
-	clockintr_trigger();
 }
 
 void
diff --git a/sys/arch/arm/include/cpu.h b/sys/arch/arm/include/cpu.h
index 986e1798cb9..1ced238694e 100644
--- a/sys/arch/arm/include/cpu.h
+++ b/sys/arch/arm/include/cpu.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpu.h,v 1.63 2023/07/25 18:16:19 cheloha Exp $	*/
+/*	$OpenBSD: cpu.h,v 1.64 2023/08/23 01:55:46 cheloha Exp $	*/
 /*	$NetBSD: cpu.h,v 1.34 2003/06/23 11:01:08 martin Exp $	*/
 
 /*
@@ -329,8 +329,6 @@ intr_restore(u_long cpsr)
 	__asm volatile ("msr cpsr_c, %0" :: "r"(cpsr));
 }
 
-void	cpu_startclock(void);
-
 #endif /* _KERNEL */
 
 #ifdef MULTIPROCESSOR