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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 47 deletions

diff --git a/arch/ia64/include/asm/timex.h b/arch/ia64/include/asm/timex.h
deleted file mode 100644
index 7ccc077a60be..000000000000
--- a/arch/ia64/include/asm/timex.h
+++ /dev/null
@@ -1,47 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _ASM_IA64_TIMEX_H
-#define _ASM_IA64_TIMEX_H
-
-/*
- * Copyright (C) 1998-2001, 2003 Hewlett-Packard Co
- *	David Mosberger-Tang <davidm@hpl.hp.com>
- */
-/*
- * 2001/01/18 davidm	Removed CLOCK_TICK_RATE.  It makes no sense on IA-64.
- *			Also removed cacheflush_time as it's entirely unused.
- */
-
-#include <asm/intrinsics.h>
-#include <asm/processor.h>
-
-typedef unsigned long cycles_t;
-
-extern void (*ia64_udelay)(unsigned long usecs);
-
-/*
- * For performance reasons, we don't want to define CLOCK_TICK_TRATE as
- * local_cpu_data->itc_rate.  Fortunately, we don't have to, either: according to George
- * Anzinger, 1/CLOCK_TICK_RATE is taken as the resolution of the timer clock.  The time
- * calculation assumes that you will use enough of these so that your tick size <= 1/HZ.
- * If the calculation shows that your CLOCK_TICK_RATE can not supply exactly 1/HZ ticks,
- * the actual value is calculated and used to update the wall clock each jiffie.  Setting
- * the CLOCK_TICK_RATE to x*HZ insures that the calculation will find no errors.  Hence we
- * pick a multiple of HZ which gives us a (totally virtual) CLOCK_TICK_RATE of about
- * 100MHz.
- */
-#define CLOCK_TICK_RATE		(HZ * 100000UL)
-
-static inline cycles_t
-get_cycles (void)
-{
-	cycles_t ret;
-
-	ret = ia64_getreg(_IA64_REG_AR_ITC);
-	return ret;
-}
-#define get_cycles get_cycles
-
-extern void ia64_cpu_local_tick (void);
-extern unsigned long long ia64_native_sched_clock (void);
-
-#endif /* _ASM_IA64_TIMEX_H */