arch: Remove Itanium (IA-64) architecture

The Itanium architecture is obsolete, and an informal survey [0] reveals
that any residual use of Itanium hardware in production is mostly HP-UX
or OpenVMS based. The use of Linux on Itanium appears to be limited to
enthusiasts that occasionally boot a fresh Linux kernel to see whether
things are still working as intended, and perhaps to churn out some
distro packages that are rarely used in practice.

None of the original companies behind Itanium still produce or support
any hardware or software for the architecture, and it is listed as
'Orphaned' in the MAINTAINERS file, as apparently, none of the engineers
that contributed on behalf of those companies (nor anyone else, for that
matter) have been willing to support or maintain the architecture
upstream or even be responsible for applying the odd fix. The Intel
firmware team removed all IA-64 support from the Tianocore/EDK2
reference implementation of EFI in 2018. (Itanium is the original
architecture for which EFI was developed, and the way Linux supports it
deviates significantly from other architectures.) Some distros, such as
Debian and Gentoo, still maintain [unofficial] ia64 ports, but many have
dropped support years ago.

While the argument is being made [1] that there is a 'for the common
good' angle to being able to build and run existing projects such as the
Grid Community Toolkit [2] on Itanium for interoperability testing, the
fact remains that none of those projects are known to be deployed on
Linux/ia64, and very few people actually have access to such a system in
the first place. Even if there were ways imaginable in which Linux/ia64
could be put to good use today, what matters is whether anyone is
actually doing that, and this does not appear to be the case.

There are no emulators widely available, and so boot testing Itanium is
generally infeasible for ordinary contributors. GCC still supports IA-64
but its compile farm [3] no longer has any IA-64 machines. GLIBC would
like to get rid of IA-64 [4] too because it would permit some overdue
code cleanups. In summary, the benefits to the ecosystem of having IA-64
be part of it are mostly theoretical, whereas the maintenance overhead
of keeping it supported is real.

So let's rip off the band aid, and remove the IA-64 arch code entirely.
This follows the timeline proposed by the Debian/ia64 maintainer [5],
which removes support in a controlled manner, leaving IA-64 in a known
good state in the most recent LTS release. Other projects will follow
once the kernel support is removed.

[0] https://lore.kernel.org/all/CAMj1kXFCMh_578jniKpUtx_j8ByHnt=s7S+yQ+vGbKt9ud7+kQ@mail.gmail.com/
[1] https://lore.kernel.org/all/0075883c-7c51-00f5-2c2d-5119c1820410@web.de/
[2] https://gridcf.org/gct-docs/latest/index.html
[3] https://cfarm.tetaneutral.net/machines/list/
[4] https://lore.kernel.org/all/87bkiilpc4.fsf@mid.deneb.enyo.de/
[5] https://lore.kernel.org/all/ff58a3e76e5102c94bb5946d99187b358def688a.camel@physik.fu-berlin.de/

Acked-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

1 files changed, 0 insertions, 463 deletions

diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
deleted file mode 100644
index 83ef044b63ef..000000000000
--- a/arch/ia64/kernel/time.c
+++ /dev/null
@@ -1,463 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * linux/arch/ia64/kernel/time.c
- *
- * Copyright (C) 1998-2003 Hewlett-Packard Co
- *	Stephane Eranian <eranian@hpl.hp.com>
- *	David Mosberger <davidm@hpl.hp.com>
- * Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
- * Copyright (C) 1999-2000 VA Linux Systems
- * Copyright (C) 1999-2000 Walt Drummond <drummond@valinux.com>
- */
-
-#include <linux/cpu.h>
-#include <linux/init.h>
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/profile.h>
-#include <linux/sched.h>
-#include <linux/time.h>
-#include <linux/nmi.h>
-#include <linux/interrupt.h>
-#include <linux/efi.h>
-#include <linux/timex.h>
-#include <linux/timekeeper_internal.h>
-#include <linux/platform_device.h>
-#include <linux/sched/cputime.h>
-
-#include <asm/cputime.h>
-#include <asm/delay.h>
-#include <asm/efi.h>
-#include <asm/hw_irq.h>
-#include <asm/ptrace.h>
-#include <asm/sal.h>
-#include <asm/sections.h>
-
-#include "fsyscall_gtod_data.h"
-#include "irq.h"
-
-static u64 itc_get_cycles(struct clocksource *cs);
-
-struct fsyscall_gtod_data_t fsyscall_gtod_data;
-
-struct itc_jitter_data_t itc_jitter_data;
-
-volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
-
-#ifdef CONFIG_IA64_DEBUG_IRQ
-
-unsigned long last_cli_ip;
-EXPORT_SYMBOL(last_cli_ip);
-
-#endif
-
-static struct clocksource clocksource_itc = {
-	.name           = "itc",
-	.rating         = 350,
-	.read           = itc_get_cycles,
-	.mask           = CLOCKSOURCE_MASK(64),
-	.flags          = CLOCK_SOURCE_IS_CONTINUOUS,
-};
-static struct clocksource *itc_clocksource;
-
-#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
-
-#include <linux/kernel_stat.h>
-
-extern u64 cycle_to_nsec(u64 cyc);
-
-void vtime_flush(struct task_struct *tsk)
-{
-	struct thread_info *ti = task_thread_info(tsk);
-	u64 delta;
-
-	if (ti->utime)
-		account_user_time(tsk, cycle_to_nsec(ti->utime));
-
-	if (ti->gtime)
-		account_guest_time(tsk, cycle_to_nsec(ti->gtime));
-
-	if (ti->idle_time)
-		account_idle_time(cycle_to_nsec(ti->idle_time));
-
-	if (ti->stime) {
-		delta = cycle_to_nsec(ti->stime);
-		account_system_index_time(tsk, delta, CPUTIME_SYSTEM);
-	}
-
-	if (ti->hardirq_time) {
-		delta = cycle_to_nsec(ti->hardirq_time);
-		account_system_index_time(tsk, delta, CPUTIME_IRQ);
-	}
-
-	if (ti->softirq_time) {
-		delta = cycle_to_nsec(ti->softirq_time);
-		account_system_index_time(tsk, delta, CPUTIME_SOFTIRQ);
-	}
-
-	ti->utime = 0;
-	ti->gtime = 0;
-	ti->idle_time = 0;
-	ti->stime = 0;
-	ti->hardirq_time = 0;
-	ti->softirq_time = 0;
-}
-
-/*
- * Called from the context switch with interrupts disabled, to charge all
- * accumulated times to the current process, and to prepare accounting on
- * the next process.
- */
-void arch_vtime_task_switch(struct task_struct *prev)
-{
-	struct thread_info *pi = task_thread_info(prev);
-	struct thread_info *ni = task_thread_info(current);
-
-	ni->ac_stamp = pi->ac_stamp;
-	ni->ac_stime = ni->ac_utime = 0;
-}
-
-/*
- * Account time for a transition between system, hard irq or soft irq state.
- * Note that this function is called with interrupts enabled.
- */
-static __u64 vtime_delta(struct task_struct *tsk)
-{
-	struct thread_info *ti = task_thread_info(tsk);
-	__u64 now, delta_stime;
-
-	WARN_ON_ONCE(!irqs_disabled());
-
-	now = ia64_get_itc();
-	delta_stime = now - ti->ac_stamp;
-	ti->ac_stamp = now;
-
-	return delta_stime;
-}
-
-void vtime_account_kernel(struct task_struct *tsk)
-{
-	struct thread_info *ti = task_thread_info(tsk);
-	__u64 stime = vtime_delta(tsk);
-
-	if (tsk->flags & PF_VCPU)
-		ti->gtime += stime;
-	else
-		ti->stime += stime;
-}
-EXPORT_SYMBOL_GPL(vtime_account_kernel);
-
-void vtime_account_idle(struct task_struct *tsk)
-{
-	struct thread_info *ti = task_thread_info(tsk);
-
-	ti->idle_time += vtime_delta(tsk);
-}
-
-void vtime_account_softirq(struct task_struct *tsk)
-{
-	struct thread_info *ti = task_thread_info(tsk);
-
-	ti->softirq_time += vtime_delta(tsk);
-}
-
-void vtime_account_hardirq(struct task_struct *tsk)
-{
-	struct thread_info *ti = task_thread_info(tsk);
-
-	ti->hardirq_time += vtime_delta(tsk);
-}
-
-#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
-
-static irqreturn_t
-timer_interrupt (int irq, void *dev_id)
-{
-	unsigned long new_itm;
-
-	if (cpu_is_offline(smp_processor_id())) {
-		return IRQ_HANDLED;
-	}
-
-	new_itm = local_cpu_data->itm_next;
-
-	if (!time_after(ia64_get_itc(), new_itm))
-		printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
-		       ia64_get_itc(), new_itm);
-
-	while (1) {
-		new_itm += local_cpu_data->itm_delta;
-
-		legacy_timer_tick(smp_processor_id() == time_keeper_id);
-
-		local_cpu_data->itm_next = new_itm;
-
-		if (time_after(new_itm, ia64_get_itc()))
-			break;
-
-		/*
-		 * Allow IPIs to interrupt the timer loop.
-		 */
-		local_irq_enable();
-		local_irq_disable();
-	}
-
-	do {
-		/*
-		 * If we're too close to the next clock tick for
-		 * comfort, we increase the safety margin by
-		 * intentionally dropping the next tick(s).  We do NOT
-		 * update itm.next because that would force us to call
-		 * xtime_update() which in turn would let our clock run
-		 * too fast (with the potentially devastating effect
-		 * of losing monotony of time).
-		 */
-		while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
-			new_itm += local_cpu_data->itm_delta;
-		ia64_set_itm(new_itm);
-		/* double check, in case we got hit by a (slow) PMI: */
-	} while (time_after_eq(ia64_get_itc(), new_itm));
-	return IRQ_HANDLED;
-}
-
-/*
- * Encapsulate access to the itm structure for SMP.
- */
-void
-ia64_cpu_local_tick (void)
-{
-	int cpu = smp_processor_id();
-	unsigned long shift = 0, delta;
-
-	/* arrange for the cycle counter to generate a timer interrupt: */
-	ia64_set_itv(IA64_TIMER_VECTOR);
-
-	delta = local_cpu_data->itm_delta;
-	/*
-	 * Stagger the timer tick for each CPU so they don't occur all at (almost) the
-	 * same time:
-	 */
-	if (cpu) {
-		unsigned long hi = 1UL << ia64_fls(cpu);
-		shift = (2*(cpu - hi) + 1) * delta/hi/2;
-	}
-	local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
-	ia64_set_itm(local_cpu_data->itm_next);
-}
-
-static int nojitter;
-
-static int __init nojitter_setup(char *str)
-{
-	nojitter = 1;
-	printk("Jitter checking for ITC timers disabled\n");
-	return 1;
-}
-
-__setup("nojitter", nojitter_setup);
-
-
-void ia64_init_itm(void)
-{
-	unsigned long platform_base_freq, itc_freq;
-	struct pal_freq_ratio itc_ratio, proc_ratio;
-	long status, platform_base_drift, itc_drift;
-
-	/*
-	 * According to SAL v2.6, we need to use a SAL call to determine the platform base
-	 * frequency and then a PAL call to determine the frequency ratio between the ITC
-	 * and the base frequency.
-	 */
-	status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
-				    &platform_base_freq, &platform_base_drift);
-	if (status != 0) {
-		printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
-	} else {
-		status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
-		if (status != 0)
-			printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
-	}
-	if (status != 0) {
-		/* invent "random" values */
-		printk(KERN_ERR
-		       "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
-		platform_base_freq = 100000000;
-		platform_base_drift = -1;	/* no drift info */
-		itc_ratio.num = 3;
-		itc_ratio.den = 1;
-	}
-	if (platform_base_freq < 40000000) {
-		printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
-		       platform_base_freq);
-		platform_base_freq = 75000000;
-		platform_base_drift = -1;
-	}
-	if (!proc_ratio.den)
-		proc_ratio.den = 1;	/* avoid division by zero */
-	if (!itc_ratio.den)
-		itc_ratio.den = 1;	/* avoid division by zero */
-
-	itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
-
-	local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
-	printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
-	       "ITC freq=%lu.%03luMHz", smp_processor_id(),
-	       platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
-	       itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
-
-	if (platform_base_drift != -1) {
-		itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
-		printk("+/-%ldppm\n", itc_drift);
-	} else {
-		itc_drift = -1;
-		printk("\n");
-	}
-
-	local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
-	local_cpu_data->itc_freq = itc_freq;
-	local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
-	local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
-					+ itc_freq/2)/itc_freq;
-
-	if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
-#ifdef CONFIG_SMP
-		/* On IA64 in an SMP configuration ITCs are never accurately synchronized.
-		 * Jitter compensation requires a cmpxchg which may limit
-		 * the scalability of the syscalls for retrieving time.
-		 * The ITC synchronization is usually successful to within a few
-		 * ITC ticks but this is not a sure thing. If you need to improve
-		 * timer performance in SMP situations then boot the kernel with the
-		 * "nojitter" option. However, doing so may result in time fluctuating (maybe
-		 * even going backward) if the ITC offsets between the individual CPUs
-		 * are too large.
-		 */
-		if (!nojitter)
-			itc_jitter_data.itc_jitter = 1;
-#endif
-	} else
-		/*
-		 * ITC is drifty and we have not synchronized the ITCs in smpboot.c.
-		 * ITC values may fluctuate significantly between processors.
-		 * Clock should not be used for hrtimers. Mark itc as only
-		 * useful for boot and testing.
-		 *
-		 * Note that jitter compensation is off! There is no point of
-		 * synchronizing ITCs since they may be large differentials
-		 * that change over time.
-		 *
-		 * The only way to fix this would be to repeatedly sync the
-		 * ITCs. Until that time we have to avoid ITC.
-		 */
-		clocksource_itc.rating = 50;
-
-	/* avoid softlock up message when cpu is unplug and plugged again. */
-	touch_softlockup_watchdog();
-
-	/* Setup the CPU local timer tick */
-	ia64_cpu_local_tick();
-
-	if (!itc_clocksource) {
-		clocksource_register_hz(&clocksource_itc,
-						local_cpu_data->itc_freq);
-		itc_clocksource = &clocksource_itc;
-	}
-}
-
-static u64 itc_get_cycles(struct clocksource *cs)
-{
-	unsigned long lcycle, now, ret;
-
-	if (!itc_jitter_data.itc_jitter)
-		return get_cycles();
-
-	lcycle = itc_jitter_data.itc_lastcycle;
-	now = get_cycles();
-	if (lcycle && time_after(lcycle, now))
-		return lcycle;
-
-	/*
-	 * Keep track of the last timer value returned.
-	 * In an SMP environment, you could lose out in contention of
-	 * cmpxchg. If so, your cmpxchg returns new value which the
-	 * winner of contention updated to. Use the new value instead.
-	 */
-	ret = cmpxchg(&itc_jitter_data.itc_lastcycle, lcycle, now);
-	if (unlikely(ret != lcycle))
-		return ret;
-
-	return now;
-}
-
-void read_persistent_clock64(struct timespec64 *ts)
-{
-	efi_gettimeofday(ts);
-}
-
-void __init
-time_init (void)
-{
-	register_percpu_irq(IA64_TIMER_VECTOR, timer_interrupt, IRQF_IRQPOLL,
-			    "timer");
-	ia64_init_itm();
-}
-
-/*
- * Generic udelay assumes that if preemption is allowed and the thread
- * migrates to another CPU, that the ITC values are synchronized across
- * all CPUs.
- */
-static void
-ia64_itc_udelay (unsigned long usecs)
-{
-	unsigned long start = ia64_get_itc();
-	unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
-
-	while (time_before(ia64_get_itc(), end))
-		cpu_relax();
-}
-
-void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
-
-void
-udelay (unsigned long usecs)
-{
-	(*ia64_udelay)(usecs);
-}
-EXPORT_SYMBOL(udelay);
-
-/* IA64 doesn't cache the timezone */
-void update_vsyscall_tz(void)
-{
-}
-
-void update_vsyscall(struct timekeeper *tk)
-{
-	write_seqcount_begin(&fsyscall_gtod_data.seq);
-
-	/* copy vsyscall data */
-	fsyscall_gtod_data.clk_mask = tk->tkr_mono.mask;
-	fsyscall_gtod_data.clk_mult = tk->tkr_mono.mult;
-	fsyscall_gtod_data.clk_shift = tk->tkr_mono.shift;
-	fsyscall_gtod_data.clk_fsys_mmio = tk->tkr_mono.clock->archdata.fsys_mmio;
-	fsyscall_gtod_data.clk_cycle_last = tk->tkr_mono.cycle_last;
-
-	fsyscall_gtod_data.wall_time.sec = tk->xtime_sec;
-	fsyscall_gtod_data.wall_time.snsec = tk->tkr_mono.xtime_nsec;
-
-	fsyscall_gtod_data.monotonic_time.sec = tk->xtime_sec
-					      + tk->wall_to_monotonic.tv_sec;
-	fsyscall_gtod_data.monotonic_time.snsec = tk->tkr_mono.xtime_nsec
-						+ ((u64)tk->wall_to_monotonic.tv_nsec
-							<< tk->tkr_mono.shift);
-
-	/* normalize */
-	while (fsyscall_gtod_data.monotonic_time.snsec >=
-					(((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
-		fsyscall_gtod_data.monotonic_time.snsec -=
-					((u64)NSEC_PER_SEC) << tk->tkr_mono.shift;
-		fsyscall_gtod_data.monotonic_time.sec++;
-	}
-
-	write_seqcount_end(&fsyscall_gtod_data.seq);
-}
-