Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1197 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
new file mode 100644
index 000000000..f6c21f6af
--- /dev/null
+++ b/arch/powerpc/kernel/time.c
@@ -0,0 +1,1197 @@
+/*
+ * Common time routines among all ppc machines.
+ *
+ * Written by Cort Dougan (cort@cs.nmt.edu) to merge
+ * Paul Mackerras' version and mine for PReP and Pmac.
+ * MPC8xx/MBX changes by Dan Malek (dmalek@jlc.net).
+ * Converted for 64-bit by Mike Corrigan (mikejc@us.ibm.com)
+ *
+ * First round of bugfixes by Gabriel Paubert (paubert@iram.es)
+ * to make clock more stable (2.4.0-test5). The only thing
+ * that this code assumes is that the timebases have been synchronized
+ * by firmware on SMP and are never stopped (never do sleep
+ * on SMP then, nap and doze are OK).
+ * 
+ * Speeded up do_gettimeofday by getting rid of references to
+ * xtime (which required locks for consistency). (mikejc@us.ibm.com)
+ *
+ * TODO (not necessarily in this file):
+ * - improve precision and reproducibility of timebase frequency
+ * measurement at boot time.
+ * - for astronomical applications: add a new function to get
+ * non ambiguous timestamps even around leap seconds. This needs
+ * a new timestamp format and a good name.
+ *
+ * 1997-09-10  Updated NTP code according to technical memorandum Jan '96
+ *             "A Kernel Model for Precision Timekeeping" by Dave Mills
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/sched/clock.h>
+#include <linux/kernel.h>
+#include <linux/param.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/interrupt.h>
+#include <linux/timex.h>
+#include <linux/kernel_stat.h>
+#include <linux/time.h>
+#include <linux/clockchips.h>
+#include <linux/init.h>
+#include <linux/profile.h>
+#include <linux/cpu.h>
+#include <linux/security.h>
+#include <linux/percpu.h>
+#include <linux/rtc.h>
+#include <linux/jiffies.h>
+#include <linux/posix-timers.h>
+#include <linux/irq.h>
+#include <linux/delay.h>
+#include <linux/irq_work.h>
+#include <linux/clk-provider.h>
+#include <linux/suspend.h>
+#include <linux/rtc.h>
+#include <linux/sched/cputime.h>
+#include <linux/processor.h>
+#include <asm/trace.h>
+
+#include <asm/io.h>
+#include <asm/nvram.h>
+#include <asm/cache.h>
+#include <asm/machdep.h>
+#include <linux/uaccess.h>
+#include <asm/time.h>
+#include <asm/prom.h>
+#include <asm/irq.h>
+#include <asm/div64.h>
+#include <asm/smp.h>
+#include <asm/vdso_datapage.h>
+#include <asm/firmware.h>
+#include <asm/asm-prototypes.h>
+
+/* powerpc clocksource/clockevent code */
+
+#include <linux/clockchips.h>
+#include <linux/timekeeper_internal.h>
+
+static u64 rtc_read(struct clocksource *);
+static struct clocksource clocksource_rtc = {
+	.name         = "rtc",
+	.rating       = 400,
+	.flags        = CLOCK_SOURCE_IS_CONTINUOUS,
+	.mask         = CLOCKSOURCE_MASK(64),
+	.read         = rtc_read,
+};
+
+static u64 timebase_read(struct clocksource *);
+static struct clocksource clocksource_timebase = {
+	.name         = "timebase",
+	.rating       = 400,
+	.flags        = CLOCK_SOURCE_IS_CONTINUOUS,
+	.mask         = CLOCKSOURCE_MASK(64),
+	.read         = timebase_read,
+};
+
+#define DECREMENTER_DEFAULT_MAX 0x7FFFFFFF
+u64 decrementer_max = DECREMENTER_DEFAULT_MAX;
+
+static int decrementer_set_next_event(unsigned long evt,
+				      struct clock_event_device *dev);
+static int decrementer_shutdown(struct clock_event_device *evt);
+
+struct clock_event_device decrementer_clockevent = {
+	.name			= "decrementer",
+	.rating			= 200,
+	.irq			= 0,
+	.set_next_event		= decrementer_set_next_event,
+	.set_state_shutdown	= decrementer_shutdown,
+	.tick_resume		= decrementer_shutdown,
+	.features		= CLOCK_EVT_FEAT_ONESHOT |
+				  CLOCK_EVT_FEAT_C3STOP,
+};
+EXPORT_SYMBOL(decrementer_clockevent);
+
+DEFINE_PER_CPU(u64, decrementers_next_tb);
+static DEFINE_PER_CPU(struct clock_event_device, decrementers);
+
+#define XSEC_PER_SEC (1024*1024)
+
+#ifdef CONFIG_PPC64
+#define SCALE_XSEC(xsec, max)	(((xsec) * max) / XSEC_PER_SEC)
+#else
+/* compute ((xsec << 12) * max) >> 32 */
+#define SCALE_XSEC(xsec, max)	mulhwu((xsec) << 12, max)
+#endif
+
+unsigned long tb_ticks_per_jiffy;
+unsigned long tb_ticks_per_usec = 100; /* sane default */
+EXPORT_SYMBOL(tb_ticks_per_usec);
+unsigned long tb_ticks_per_sec;
+EXPORT_SYMBOL(tb_ticks_per_sec);	/* for cputime_t conversions */
+
+DEFINE_SPINLOCK(rtc_lock);
+EXPORT_SYMBOL_GPL(rtc_lock);
+
+static u64 tb_to_ns_scale __read_mostly;
+static unsigned tb_to_ns_shift __read_mostly;
+static u64 boot_tb __read_mostly;
+
+extern struct timezone sys_tz;
+static long timezone_offset;
+
+unsigned long ppc_proc_freq;
+EXPORT_SYMBOL_GPL(ppc_proc_freq);
+unsigned long ppc_tb_freq;
+EXPORT_SYMBOL_GPL(ppc_tb_freq);
+
+#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
+/*
+ * Factor for converting from cputime_t (timebase ticks) to
+ * microseconds. This is stored as 0.64 fixed-point binary fraction.
+ */
+u64 __cputime_usec_factor;
+EXPORT_SYMBOL(__cputime_usec_factor);
+
+#ifdef CONFIG_PPC_SPLPAR
+void (*dtl_consumer)(struct dtl_entry *, u64);
+#endif
+
+static void calc_cputime_factors(void)
+{
+	struct div_result res;
+
+	div128_by_32(1000000, 0, tb_ticks_per_sec, &res);
+	__cputime_usec_factor = res.result_low;
+}
+
+/*
+ * Read the SPURR on systems that have it, otherwise the PURR,
+ * or if that doesn't exist return the timebase value passed in.
+ */
+static unsigned long read_spurr(unsigned long tb)
+{
+	if (cpu_has_feature(CPU_FTR_SPURR))
+		return mfspr(SPRN_SPURR);
+	if (cpu_has_feature(CPU_FTR_PURR))
+		return mfspr(SPRN_PURR);
+	return tb;
+}
+
+#ifdef CONFIG_PPC_SPLPAR
+
+/*
+ * Scan the dispatch trace log and count up the stolen time.
+ * Should be called with interrupts disabled.
+ */
+static u64 scan_dispatch_log(u64 stop_tb)
+{
+	u64 i = local_paca->dtl_ridx;
+	struct dtl_entry *dtl = local_paca->dtl_curr;
+	struct dtl_entry *dtl_end = local_paca->dispatch_log_end;
+	struct lppaca *vpa = local_paca->lppaca_ptr;
+	u64 tb_delta;
+	u64 stolen = 0;
+	u64 dtb;
+
+	if (!dtl)
+		return 0;
+
+	if (i == be64_to_cpu(vpa->dtl_idx))
+		return 0;
+	while (i < be64_to_cpu(vpa->dtl_idx)) {
+		dtb = be64_to_cpu(dtl->timebase);
+		tb_delta = be32_to_cpu(dtl->enqueue_to_dispatch_time) +
+			be32_to_cpu(dtl->ready_to_enqueue_time);
+		barrier();
+		if (i + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx)) {
+			/* buffer has overflowed */
+			i = be64_to_cpu(vpa->dtl_idx) - N_DISPATCH_LOG;
+			dtl = local_paca->dispatch_log + (i % N_DISPATCH_LOG);
+			continue;
+		}
+		if (dtb > stop_tb)
+			break;
+		if (dtl_consumer)
+			dtl_consumer(dtl, i);
+		stolen += tb_delta;
+		++i;
+		++dtl;
+		if (dtl == dtl_end)
+			dtl = local_paca->dispatch_log;
+	}
+	local_paca->dtl_ridx = i;
+	local_paca->dtl_curr = dtl;
+	return stolen;
+}
+
+/*
+ * Accumulate stolen time by scanning the dispatch trace log.
+ * Called on entry from user mode.
+ */
+void notrace accumulate_stolen_time(void)
+{
+	u64 sst, ust;
+	unsigned long save_irq_soft_mask = irq_soft_mask_return();
+	struct cpu_accounting_data *acct = &local_paca->accounting;
+
+	/* We are called early in the exception entry, before
+	 * soft/hard_enabled are sync'ed to the expected state
+	 * for the exception. We are hard disabled but the PACA
+	 * needs to reflect that so various debug stuff doesn't
+	 * complain
+	 */
+	irq_soft_mask_set(IRQS_DISABLED);
+
+	sst = scan_dispatch_log(acct->starttime_user);
+	ust = scan_dispatch_log(acct->starttime);
+	acct->stime -= sst;
+	acct->utime -= ust;
+	acct->steal_time += ust + sst;
+
+	irq_soft_mask_set(save_irq_soft_mask);
+}
+
+static inline u64 calculate_stolen_time(u64 stop_tb)
+{
+	if (!firmware_has_feature(FW_FEATURE_SPLPAR))
+		return 0;
+
+	if (get_paca()->dtl_ridx != be64_to_cpu(get_lppaca()->dtl_idx))
+		return scan_dispatch_log(stop_tb);
+
+	return 0;
+}
+
+#else /* CONFIG_PPC_SPLPAR */
+static inline u64 calculate_stolen_time(u64 stop_tb)
+{
+	return 0;
+}
+
+#endif /* CONFIG_PPC_SPLPAR */
+
+/*
+ * Account time for a transition between system, hard irq
+ * or soft irq state.
+ */
+static unsigned long vtime_delta(struct task_struct *tsk,
+				 unsigned long *stime_scaled,
+				 unsigned long *steal_time)
+{
+	unsigned long now, nowscaled, deltascaled;
+	unsigned long stime;
+	unsigned long utime, utime_scaled;
+	struct cpu_accounting_data *acct = get_accounting(tsk);
+
+	WARN_ON_ONCE(!irqs_disabled());
+
+	now = mftb();
+	nowscaled = read_spurr(now);
+	stime = now - acct->starttime;
+	acct->starttime = now;
+	deltascaled = nowscaled - acct->startspurr;
+	acct->startspurr = nowscaled;
+
+	*steal_time = calculate_stolen_time(now);
+
+	utime = acct->utime - acct->utime_sspurr;
+	acct->utime_sspurr = acct->utime;
+
+	/*
+	 * Because we don't read the SPURR on every kernel entry/exit,
+	 * deltascaled includes both user and system SPURR ticks.
+	 * Apportion these ticks to system SPURR ticks and user
+	 * SPURR ticks in the same ratio as the system time (delta)
+	 * and user time (udelta) values obtained from the timebase
+	 * over the same interval.  The system ticks get accounted here;
+	 * the user ticks get saved up in paca->user_time_scaled to be
+	 * used by account_process_tick.
+	 */
+	*stime_scaled = stime;
+	utime_scaled = utime;
+	if (deltascaled != stime + utime) {
+		if (utime) {
+			*stime_scaled = deltascaled * stime / (stime + utime);
+			utime_scaled = deltascaled - *stime_scaled;
+		} else {
+			*stime_scaled = deltascaled;
+		}
+	}
+	acct->utime_scaled += utime_scaled;
+
+	return stime;
+}
+
+void vtime_account_system(struct task_struct *tsk)
+{
+	unsigned long stime, stime_scaled, steal_time;
+	struct cpu_accounting_data *acct = get_accounting(tsk);
+
+	stime = vtime_delta(tsk, &stime_scaled, &steal_time);
+
+	stime -= min(stime, steal_time);
+	acct->steal_time += steal_time;
+
+	if ((tsk->flags & PF_VCPU) && !irq_count()) {
+		acct->gtime += stime;
+		acct->utime_scaled += stime_scaled;
+	} else {
+		if (hardirq_count())
+			acct->hardirq_time += stime;
+		else if (in_serving_softirq())
+			acct->softirq_time += stime;
+		else
+			acct->stime += stime;
+
+		acct->stime_scaled += stime_scaled;
+	}
+}
+EXPORT_SYMBOL_GPL(vtime_account_system);
+
+void vtime_account_idle(struct task_struct *tsk)
+{
+	unsigned long stime, stime_scaled, steal_time;
+	struct cpu_accounting_data *acct = get_accounting(tsk);
+
+	stime = vtime_delta(tsk, &stime_scaled, &steal_time);
+	acct->idle_time += stime + steal_time;
+}
+
+/*
+ * Account the whole cputime accumulated in the paca
+ * Must be called with interrupts disabled.
+ * Assumes that vtime_account_system/idle() has been called
+ * recently (i.e. since the last entry from usermode) so that
+ * get_paca()->user_time_scaled is up to date.
+ */
+void vtime_flush(struct task_struct *tsk)
+{
+	struct cpu_accounting_data *acct = get_accounting(tsk);
+
+	if (acct->utime)
+		account_user_time(tsk, cputime_to_nsecs(acct->utime));
+
+	if (acct->utime_scaled)
+		tsk->utimescaled += cputime_to_nsecs(acct->utime_scaled);
+
+	if (acct->gtime)
+		account_guest_time(tsk, cputime_to_nsecs(acct->gtime));
+
+	if (acct->steal_time)
+		account_steal_time(cputime_to_nsecs(acct->steal_time));
+
+	if (acct->idle_time)
+		account_idle_time(cputime_to_nsecs(acct->idle_time));
+
+	if (acct->stime)
+		account_system_index_time(tsk, cputime_to_nsecs(acct->stime),
+					  CPUTIME_SYSTEM);
+	if (acct->stime_scaled)
+		tsk->stimescaled += cputime_to_nsecs(acct->stime_scaled);
+
+	if (acct->hardirq_time)
+		account_system_index_time(tsk, cputime_to_nsecs(acct->hardirq_time),
+					  CPUTIME_IRQ);
+	if (acct->softirq_time)
+		account_system_index_time(tsk, cputime_to_nsecs(acct->softirq_time),
+					  CPUTIME_SOFTIRQ);
+
+	acct->utime = 0;
+	acct->utime_scaled = 0;
+	acct->utime_sspurr = 0;
+	acct->gtime = 0;
+	acct->steal_time = 0;
+	acct->idle_time = 0;
+	acct->stime = 0;
+	acct->stime_scaled = 0;
+	acct->hardirq_time = 0;
+	acct->softirq_time = 0;
+}
+
+#else /* ! CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
+#define calc_cputime_factors()
+#endif
+
+void __delay(unsigned long loops)
+{
+	unsigned long start;
+	int diff;
+
+	spin_begin();
+	if (__USE_RTC()) {
+		start = get_rtcl();
+		do {
+			/* the RTCL register wraps at 1000000000 */
+			diff = get_rtcl() - start;
+			if (diff < 0)
+				diff += 1000000000;
+			spin_cpu_relax();
+		} while (diff < loops);
+	} else {
+		start = get_tbl();
+		while (get_tbl() - start < loops)
+			spin_cpu_relax();
+	}
+	spin_end();
+}
+EXPORT_SYMBOL(__delay);
+
+void udelay(unsigned long usecs)
+{
+	__delay(tb_ticks_per_usec * usecs);
+}
+EXPORT_SYMBOL(udelay);
+
+#ifdef CONFIG_SMP
+unsigned long profile_pc(struct pt_regs *regs)
+{
+	unsigned long pc = instruction_pointer(regs);
+
+	if (in_lock_functions(pc))
+		return regs->link;
+
+	return pc;
+}
+EXPORT_SYMBOL(profile_pc);
+#endif
+
+#ifdef CONFIG_IRQ_WORK
+
+/*
+ * 64-bit uses a byte in the PACA, 32-bit uses a per-cpu variable...
+ */
+#ifdef CONFIG_PPC64
+static inline unsigned long test_irq_work_pending(void)
+{
+	unsigned long x;
+
+	asm volatile("lbz %0,%1(13)"
+		: "=r" (x)
+		: "i" (offsetof(struct paca_struct, irq_work_pending)));
+	return x;
+}
+
+static inline void set_irq_work_pending_flag(void)
+{
+	asm volatile("stb %0,%1(13)" : :
+		"r" (1),
+		"i" (offsetof(struct paca_struct, irq_work_pending)));
+}
+
+static inline void clear_irq_work_pending(void)
+{
+	asm volatile("stb %0,%1(13)" : :
+		"r" (0),
+		"i" (offsetof(struct paca_struct, irq_work_pending)));
+}
+
+#else /* 32-bit */
+
+DEFINE_PER_CPU(u8, irq_work_pending);
+
+#define set_irq_work_pending_flag()	__this_cpu_write(irq_work_pending, 1)
+#define test_irq_work_pending()		__this_cpu_read(irq_work_pending)
+#define clear_irq_work_pending()	__this_cpu_write(irq_work_pending, 0)
+
+#endif /* 32 vs 64 bit */
+
+void arch_irq_work_raise(void)
+{
+	/*
+	 * 64-bit code that uses irq soft-mask can just cause an immediate
+	 * interrupt here that gets soft masked, if this is called under
+	 * local_irq_disable(). It might be possible to prevent that happening
+	 * by noticing interrupts are disabled and setting decrementer pending
+	 * to be replayed when irqs are enabled. The problem there is that
+	 * tracing can call irq_work_raise, including in code that does low
+	 * level manipulations of irq soft-mask state (e.g., trace_hardirqs_on)
+	 * which could get tangled up if we're messing with the same state
+	 * here.
+	 */
+	preempt_disable();
+	set_irq_work_pending_flag();
+	set_dec(1);
+	preempt_enable();
+}
+
+#else  /* CONFIG_IRQ_WORK */
+
+#define test_irq_work_pending()	0
+#define clear_irq_work_pending()
+
+#endif /* CONFIG_IRQ_WORK */
+
+/*
+ * timer_interrupt - gets called when the decrementer overflows,
+ * with interrupts disabled.
+ */
+void timer_interrupt(struct pt_regs *regs)
+{
+	struct clock_event_device *evt = this_cpu_ptr(&decrementers);
+	u64 *next_tb = this_cpu_ptr(&decrementers_next_tb);
+	struct pt_regs *old_regs;
+	u64 now;
+
+	/* Some implementations of hotplug will get timer interrupts while
+	 * offline, just ignore these and we also need to set
+	 * decrementers_next_tb as MAX to make sure __check_irq_replay
+	 * don't replay timer interrupt when return, otherwise we'll trap
+	 * here infinitely :(
+	 */
+	if (unlikely(!cpu_online(smp_processor_id()))) {
+		*next_tb = ~(u64)0;
+		set_dec(decrementer_max);
+		return;
+	}
+
+	/* Ensure a positive value is written to the decrementer, or else
+	 * some CPUs will continue to take decrementer exceptions. When the
+	 * PPC_WATCHDOG (decrementer based) is configured, keep this at most
+	 * 31 bits, which is about 4 seconds on most systems, which gives
+	 * the watchdog a chance of catching timer interrupt hard lockups.
+	 */
+	if (IS_ENABLED(CONFIG_PPC_WATCHDOG))
+		set_dec(0x7fffffff);
+	else
+		set_dec(decrementer_max);
+
+	/* Conditionally hard-enable interrupts now that the DEC has been
+	 * bumped to its maximum value
+	 */
+	may_hard_irq_enable();
+
+
+#if defined(CONFIG_PPC32) && defined(CONFIG_PPC_PMAC)
+	if (atomic_read(&ppc_n_lost_interrupts) != 0)
+		do_IRQ(regs);
+#endif
+
+	old_regs = set_irq_regs(regs);
+	irq_enter();
+	trace_timer_interrupt_entry(regs);
+
+	if (test_irq_work_pending()) {
+		clear_irq_work_pending();
+		irq_work_run();
+	}
+
+	now = get_tb_or_rtc();
+	if (now >= *next_tb) {
+		*next_tb = ~(u64)0;
+		if (evt->event_handler)
+			evt->event_handler(evt);
+		__this_cpu_inc(irq_stat.timer_irqs_event);
+	} else {
+		now = *next_tb - now;
+		if (now <= decrementer_max)
+			set_dec(now);
+		/* We may have raced with new irq work */
+		if (test_irq_work_pending())
+			set_dec(1);
+		__this_cpu_inc(irq_stat.timer_irqs_others);
+	}
+
+	trace_timer_interrupt_exit(regs);
+	irq_exit();
+	set_irq_regs(old_regs);
+}
+EXPORT_SYMBOL(timer_interrupt);
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
+void timer_broadcast_interrupt(void)
+{
+	u64 *next_tb = this_cpu_ptr(&decrementers_next_tb);
+
+	*next_tb = ~(u64)0;
+	tick_receive_broadcast();
+	__this_cpu_inc(irq_stat.broadcast_irqs_event);
+}
+#endif
+
+/*
+ * Hypervisor decrementer interrupts shouldn't occur but are sometimes
+ * left pending on exit from a KVM guest.  We don't need to do anything
+ * to clear them, as they are edge-triggered.
+ */
+void hdec_interrupt(struct pt_regs *regs)
+{
+}
+
+#ifdef CONFIG_SUSPEND
+static void generic_suspend_disable_irqs(void)
+{
+	/* Disable the decrementer, so that it doesn't interfere
+	 * with suspending.
+	 */
+
+	set_dec(decrementer_max);
+	local_irq_disable();
+	set_dec(decrementer_max);
+}
+
+static void generic_suspend_enable_irqs(void)
+{
+	local_irq_enable();
+}
+
+/* Overrides the weak version in kernel/power/main.c */
+void arch_suspend_disable_irqs(void)
+{
+	if (ppc_md.suspend_disable_irqs)
+		ppc_md.suspend_disable_irqs();
+	generic_suspend_disable_irqs();
+}
+
+/* Overrides the weak version in kernel/power/main.c */
+void arch_suspend_enable_irqs(void)
+{
+	generic_suspend_enable_irqs();
+	if (ppc_md.suspend_enable_irqs)
+		ppc_md.suspend_enable_irqs();
+}
+#endif
+
+unsigned long long tb_to_ns(unsigned long long ticks)
+{
+	return mulhdu(ticks, tb_to_ns_scale) << tb_to_ns_shift;
+}
+EXPORT_SYMBOL_GPL(tb_to_ns);
+
+/*
+ * Scheduler clock - returns current time in nanosec units.
+ *
+ * Note: mulhdu(a, b) (multiply high double unsigned) returns
+ * the high 64 bits of a * b, i.e. (a * b) >> 64, where a and b
+ * are 64-bit unsigned numbers.
+ */
+notrace unsigned long long sched_clock(void)
+{
+	if (__USE_RTC())
+		return get_rtc();
+	return mulhdu(get_tb() - boot_tb, tb_to_ns_scale) << tb_to_ns_shift;
+}
+
+
+#ifdef CONFIG_PPC_PSERIES
+
+/*
+ * Running clock - attempts to give a view of time passing for a virtualised
+ * kernels.
+ * Uses the VTB register if available otherwise a next best guess.
+ */
+unsigned long long running_clock(void)
+{
+	/*
+	 * Don't read the VTB as a host since KVM does not switch in host
+	 * timebase into the VTB when it takes a guest off the CPU, reading the
+	 * VTB would result in reading 'last switched out' guest VTB.
+	 *
+	 * Host kernels are often compiled with CONFIG_PPC_PSERIES checked, it
+	 * would be unsafe to rely only on the #ifdef above.
+	 */
+	if (firmware_has_feature(FW_FEATURE_LPAR) &&
+	    cpu_has_feature(CPU_FTR_ARCH_207S))
+		return mulhdu(get_vtb() - boot_tb, tb_to_ns_scale) << tb_to_ns_shift;
+
+	/*
+	 * This is a next best approximation without a VTB.
+	 * On a host which is running bare metal there should never be any stolen
+	 * time and on a host which doesn't do any virtualisation TB *should* equal
+	 * VTB so it makes no difference anyway.
+	 */
+	return local_clock() - kcpustat_this_cpu->cpustat[CPUTIME_STEAL];
+}
+#endif
+
+static int __init get_freq(char *name, int cells, unsigned long *val)
+{
+	struct device_node *cpu;
+	const __be32 *fp;
+	int found = 0;
+
+	/* The cpu node should have timebase and clock frequency properties */
+	cpu = of_find_node_by_type(NULL, "cpu");
+
+	if (cpu) {
+		fp = of_get_property(cpu, name, NULL);
+		if (fp) {
+			found = 1;
+			*val = of_read_ulong(fp, cells);
+		}
+
+		of_node_put(cpu);
+	}
+
+	return found;
+}
+
+static void start_cpu_decrementer(void)
+{
+#if defined(CONFIG_BOOKE) || defined(CONFIG_40x)
+	unsigned int tcr;
+
+	/* Clear any pending timer interrupts */
+	mtspr(SPRN_TSR, TSR_ENW | TSR_WIS | TSR_DIS | TSR_FIS);
+
+	tcr = mfspr(SPRN_TCR);
+	/*
+	 * The watchdog may have already been enabled by u-boot. So leave
+	 * TRC[WP] (Watchdog Period) alone.
+	 */
+	tcr &= TCR_WP_MASK;	/* Clear all bits except for TCR[WP] */
+	tcr |= TCR_DIE;		/* Enable decrementer */
+	mtspr(SPRN_TCR, tcr);
+#endif
+}
+
+void __init generic_calibrate_decr(void)
+{
+	ppc_tb_freq = DEFAULT_TB_FREQ;		/* hardcoded default */
+
+	if (!get_freq("ibm,extended-timebase-frequency", 2, &ppc_tb_freq) &&
+	    !get_freq("timebase-frequency", 1, &ppc_tb_freq)) {
+
+		printk(KERN_ERR "WARNING: Estimating decrementer frequency "
+				"(not found)\n");
+	}
+
+	ppc_proc_freq = DEFAULT_PROC_FREQ;	/* hardcoded default */
+
+	if (!get_freq("ibm,extended-clock-frequency", 2, &ppc_proc_freq) &&
+	    !get_freq("clock-frequency", 1, &ppc_proc_freq)) {
+
+		printk(KERN_ERR "WARNING: Estimating processor frequency "
+				"(not found)\n");
+	}
+}
+
+int update_persistent_clock64(struct timespec64 now)
+{
+	struct rtc_time tm;
+
+	if (!ppc_md.set_rtc_time)
+		return -ENODEV;
+
+	rtc_time64_to_tm(now.tv_sec + 1 + timezone_offset, &tm);
+
+	return ppc_md.set_rtc_time(&tm);
+}
+
+static void __read_persistent_clock(struct timespec64 *ts)
+{
+	struct rtc_time tm;
+	static int first = 1;
+
+	ts->tv_nsec = 0;
+	/* XXX this is a litle fragile but will work okay in the short term */
+	if (first) {
+		first = 0;
+		if (ppc_md.time_init)
+			timezone_offset = ppc_md.time_init();
+
+		/* get_boot_time() isn't guaranteed to be safe to call late */
+		if (ppc_md.get_boot_time) {
+			ts->tv_sec = ppc_md.get_boot_time() - timezone_offset;
+			return;
+		}
+	}
+	if (!ppc_md.get_rtc_time) {
+		ts->tv_sec = 0;
+		return;
+	}
+	ppc_md.get_rtc_time(&tm);
+
+	ts->tv_sec = rtc_tm_to_time64(&tm);
+}
+
+void read_persistent_clock64(struct timespec64 *ts)
+{
+	__read_persistent_clock(ts);
+
+	/* Sanitize it in case real time clock is set below EPOCH */
+	if (ts->tv_sec < 0) {
+		ts->tv_sec = 0;
+		ts->tv_nsec = 0;
+	}
+		
+}
+
+/* clocksource code */
+static notrace u64 rtc_read(struct clocksource *cs)
+{
+	return (u64)get_rtc();
+}
+
+static notrace u64 timebase_read(struct clocksource *cs)
+{
+	return (u64)get_tb();
+}
+
+
+void update_vsyscall(struct timekeeper *tk)
+{
+	struct timespec xt;
+	struct clocksource *clock = tk->tkr_mono.clock;
+	u32 mult = tk->tkr_mono.mult;
+	u32 shift = tk->tkr_mono.shift;
+	u64 cycle_last = tk->tkr_mono.cycle_last;
+	u64 new_tb_to_xs, new_stamp_xsec;
+	u64 frac_sec;
+
+	if (clock != &clocksource_timebase)
+		return;
+
+	xt.tv_sec = tk->xtime_sec;
+	xt.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
+
+	/* Make userspace gettimeofday spin until we're done. */
+	++vdso_data->tb_update_count;
+	smp_mb();
+
+	/*
+	 * This computes ((2^20 / 1e9) * mult) >> shift as a
+	 * 0.64 fixed-point fraction.
+	 * The computation in the else clause below won't overflow
+	 * (as long as the timebase frequency is >= 1.049 MHz)
+	 * but loses precision because we lose the low bits of the constant
+	 * in the shift.  Note that 19342813113834067 ~= 2^(20+64) / 1e9.
+	 * For a shift of 24 the error is about 0.5e-9, or about 0.5ns
+	 * over a second.  (Shift values are usually 22, 23 or 24.)
+	 * For high frequency clocks such as the 512MHz timebase clock
+	 * on POWER[6789], the mult value is small (e.g. 32768000)
+	 * and so we can shift the constant by 16 initially
+	 * (295147905179 ~= 2^(20+64-16) / 1e9) and then do the
+	 * remaining shifts after the multiplication, which gives a
+	 * more accurate result (e.g. with mult = 32768000, shift = 24,
+	 * the error is only about 1.2e-12, or 0.7ns over 10 minutes).
+	 */
+	if (mult <= 62500000 && clock->shift >= 16)
+		new_tb_to_xs = ((u64) mult * 295147905179ULL) >> (clock->shift - 16);
+	else
+		new_tb_to_xs = (u64) mult * (19342813113834067ULL >> clock->shift);
+
+	/*
+	 * Compute the fractional second in units of 2^-32 seconds.
+	 * The fractional second is tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift
+	 * in nanoseconds, so multiplying that by 2^32 / 1e9 gives
+	 * it in units of 2^-32 seconds.
+	 * We assume shift <= 32 because clocks_calc_mult_shift()
+	 * generates shift values in the range 0 - 32.
+	 */
+	frac_sec = tk->tkr_mono.xtime_nsec << (32 - shift);
+	do_div(frac_sec, NSEC_PER_SEC);
+
+	/*
+	 * Work out new stamp_xsec value for any legacy users of systemcfg.
+	 * stamp_xsec is in units of 2^-20 seconds.
+	 */
+	new_stamp_xsec = frac_sec >> 12;
+	new_stamp_xsec += tk->xtime_sec * XSEC_PER_SEC;
+
+	/*
+	 * tb_update_count is used to allow the userspace gettimeofday code
+	 * to assure itself that it sees a consistent view of the tb_to_xs and
+	 * stamp_xsec variables.  It reads the tb_update_count, then reads
+	 * tb_to_xs and stamp_xsec and then reads tb_update_count again.  If
+	 * the two values of tb_update_count match and are even then the
+	 * tb_to_xs and stamp_xsec values are consistent.  If not, then it
+	 * loops back and reads them again until this criteria is met.
+	 */
+	vdso_data->tb_orig_stamp = cycle_last;
+	vdso_data->stamp_xsec = new_stamp_xsec;
+	vdso_data->tb_to_xs = new_tb_to_xs;
+	vdso_data->wtom_clock_sec = tk->wall_to_monotonic.tv_sec;
+	vdso_data->wtom_clock_nsec = tk->wall_to_monotonic.tv_nsec;
+	vdso_data->stamp_xtime = xt;
+	vdso_data->stamp_sec_fraction = frac_sec;
+	vdso_data->hrtimer_res = hrtimer_resolution;
+	smp_wmb();
+	++(vdso_data->tb_update_count);
+}
+
+void update_vsyscall_tz(void)
+{
+	vdso_data->tz_minuteswest = sys_tz.tz_minuteswest;
+	vdso_data->tz_dsttime = sys_tz.tz_dsttime;
+}
+
+static void __init clocksource_init(void)
+{
+	struct clocksource *clock;
+
+	if (__USE_RTC())
+		clock = &clocksource_rtc;
+	else
+		clock = &clocksource_timebase;
+
+	if (clocksource_register_hz(clock, tb_ticks_per_sec)) {
+		printk(KERN_ERR "clocksource: %s is already registered\n",
+		       clock->name);
+		return;
+	}
+
+	printk(KERN_INFO "clocksource: %s mult[%x] shift[%d] registered\n",
+	       clock->name, clock->mult, clock->shift);
+}
+
+static int decrementer_set_next_event(unsigned long evt,
+				      struct clock_event_device *dev)
+{
+	__this_cpu_write(decrementers_next_tb, get_tb_or_rtc() + evt);
+	set_dec(evt);
+
+	/* We may have raced with new irq work */
+	if (test_irq_work_pending())
+		set_dec(1);
+
+	return 0;
+}
+
+static int decrementer_shutdown(struct clock_event_device *dev)
+{
+	decrementer_set_next_event(decrementer_max, dev);
+	return 0;
+}
+
+static void register_decrementer_clockevent(int cpu)
+{
+	struct clock_event_device *dec = &per_cpu(decrementers, cpu);
+
+	*dec = decrementer_clockevent;
+	dec->cpumask = cpumask_of(cpu);
+
+	clockevents_config_and_register(dec, ppc_tb_freq, 2, decrementer_max);
+
+	printk_once(KERN_DEBUG "clockevent: %s mult[%x] shift[%d] cpu[%d]\n",
+		    dec->name, dec->mult, dec->shift, cpu);
+
+	/* Set values for KVM, see kvm_emulate_dec() */
+	decrementer_clockevent.mult = dec->mult;
+	decrementer_clockevent.shift = dec->shift;
+}
+
+static void enable_large_decrementer(void)
+{
+	if (!cpu_has_feature(CPU_FTR_ARCH_300))
+		return;
+
+	if (decrementer_max <= DECREMENTER_DEFAULT_MAX)
+		return;
+
+	/*
+	 * If we're running as the hypervisor we need to enable the LD manually
+	 * otherwise firmware should have done it for us.
+	 */
+	if (cpu_has_feature(CPU_FTR_HVMODE))
+		mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) | LPCR_LD);
+}
+
+static void __init set_decrementer_max(void)
+{
+	struct device_node *cpu;
+	u32 bits = 32;
+
+	/* Prior to ISAv3 the decrementer is always 32 bit */
+	if (!cpu_has_feature(CPU_FTR_ARCH_300))
+		return;
+
+	cpu = of_find_node_by_type(NULL, "cpu");
+
+	if (of_property_read_u32(cpu, "ibm,dec-bits", &bits) == 0) {
+		if (bits > 64 || bits < 32) {
+			pr_warn("time_init: firmware supplied invalid ibm,dec-bits");
+			bits = 32;
+		}
+
+		/* calculate the signed maximum given this many bits */
+		decrementer_max = (1ul << (bits - 1)) - 1;
+	}
+
+	of_node_put(cpu);
+
+	pr_info("time_init: %u bit decrementer (max: %llx)\n",
+		bits, decrementer_max);
+}
+
+static void __init init_decrementer_clockevent(void)
+{
+	register_decrementer_clockevent(smp_processor_id());
+}
+
+void secondary_cpu_time_init(void)
+{
+	/* Enable and test the large decrementer for this cpu */
+	enable_large_decrementer();
+
+	/* Start the decrementer on CPUs that have manual control
+	 * such as BookE
+	 */
+	start_cpu_decrementer();
+
+	/* FIME: Should make unrelatred change to move snapshot_timebase
+	 * call here ! */
+	register_decrementer_clockevent(smp_processor_id());
+}
+
+/* This function is only called on the boot processor */
+void __init time_init(void)
+{
+	struct div_result res;
+	u64 scale;
+	unsigned shift;
+
+	if (__USE_RTC()) {
+		/* 601 processor: dec counts down by 128 every 128ns */
+		ppc_tb_freq = 1000000000;
+	} else {
+		/* Normal PowerPC with timebase register */
+		ppc_md.calibrate_decr();
+		printk(KERN_DEBUG "time_init: decrementer frequency = %lu.%.6lu MHz\n",
+		       ppc_tb_freq / 1000000, ppc_tb_freq % 1000000);
+		printk(KERN_DEBUG "time_init: processor frequency   = %lu.%.6lu MHz\n",
+		       ppc_proc_freq / 1000000, ppc_proc_freq % 1000000);
+	}
+
+	tb_ticks_per_jiffy = ppc_tb_freq / HZ;
+	tb_ticks_per_sec = ppc_tb_freq;
+	tb_ticks_per_usec = ppc_tb_freq / 1000000;
+	calc_cputime_factors();
+
+	/*
+	 * Compute scale factor for sched_clock.
+	 * The calibrate_decr() function has set tb_ticks_per_sec,
+	 * which is the timebase frequency.
+	 * We compute 1e9 * 2^64 / tb_ticks_per_sec and interpret
+	 * the 128-bit result as a 64.64 fixed-point number.
+	 * We then shift that number right until it is less than 1.0,
+	 * giving us the scale factor and shift count to use in
+	 * sched_clock().
+	 */
+	div128_by_32(1000000000, 0, tb_ticks_per_sec, &res);
+	scale = res.result_low;
+	for (shift = 0; res.result_high != 0; ++shift) {
+		scale = (scale >> 1) | (res.result_high << 63);
+		res.result_high >>= 1;
+	}
+	tb_to_ns_scale = scale;
+	tb_to_ns_shift = shift;
+	/* Save the current timebase to pretty up CONFIG_PRINTK_TIME */
+	boot_tb = get_tb_or_rtc();
+
+	/* If platform provided a timezone (pmac), we correct the time */
+	if (timezone_offset) {
+		sys_tz.tz_minuteswest = -timezone_offset / 60;
+		sys_tz.tz_dsttime = 0;
+	}
+
+	vdso_data->tb_update_count = 0;
+	vdso_data->tb_ticks_per_sec = tb_ticks_per_sec;
+
+	/* initialise and enable the large decrementer (if we have one) */
+	set_decrementer_max();
+	enable_large_decrementer();
+
+	/* Start the decrementer on CPUs that have manual control
+	 * such as BookE
+	 */
+	start_cpu_decrementer();
+
+	/* Register the clocksource */
+	clocksource_init();
+
+	init_decrementer_clockevent();
+	tick_setup_hrtimer_broadcast();
+
+#ifdef CONFIG_COMMON_CLK
+	of_clk_init(NULL);
+#endif
+}
+
+/*
+ * Divide a 128-bit dividend by a 32-bit divisor, leaving a 128 bit
+ * result.
+ */
+void div128_by_32(u64 dividend_high, u64 dividend_low,
+		  unsigned divisor, struct div_result *dr)
+{
+	unsigned long a, b, c, d;
+	unsigned long w, x, y, z;
+	u64 ra, rb, rc;
+
+	a = dividend_high >> 32;
+	b = dividend_high & 0xffffffff;
+	c = dividend_low >> 32;
+	d = dividend_low & 0xffffffff;
+
+	w = a / divisor;
+	ra = ((u64)(a - (w * divisor)) << 32) + b;
+
+	rb = ((u64) do_div(ra, divisor) << 32) + c;
+	x = ra;
+
+	rc = ((u64) do_div(rb, divisor) << 32) + d;
+	y = rb;
+
+	do_div(rc, divisor);
+	z = rc;
+
+	dr->result_high = ((u64)w << 32) + x;
+	dr->result_low  = ((u64)y << 32) + z;
+
+}
+
+/* We don't need to calibrate delay, we use the CPU timebase for that */
+void calibrate_delay(void)
+{
+	/* Some generic code (such as spinlock debug) use loops_per_jiffy
+	 * as the number of __delay(1) in a jiffy, so make it so
+	 */
+	loops_per_jiffy = tb_ticks_per_jiffy;
+}
+
+#if IS_ENABLED(CONFIG_RTC_DRV_GENERIC)
+static int rtc_generic_get_time(struct device *dev, struct rtc_time *tm)
+{
+	ppc_md.get_rtc_time(tm);
+	return 0;
+}
+
+static int rtc_generic_set_time(struct device *dev, struct rtc_time *tm)
+{
+	if (!ppc_md.set_rtc_time)
+		return -EOPNOTSUPP;
+
+	if (ppc_md.set_rtc_time(tm) < 0)
+		return -EOPNOTSUPP;
+
+	return 0;
+}
+
+static const struct rtc_class_ops rtc_generic_ops = {
+	.read_time = rtc_generic_get_time,
+	.set_time = rtc_generic_set_time,
+};
+
+static int __init rtc_init(void)
+{
+	struct platform_device *pdev;
+
+	if (!ppc_md.get_rtc_time)
+		return -ENODEV;
+
+	pdev = platform_device_register_data(NULL, "rtc-generic", -1,
+					     &rtc_generic_ops,
+					     sizeof(rtc_generic_ops));
+
+	return PTR_ERR_OR_ZERO(pdev);
+}
+
+device_initcall(rtc_init);
+#endif