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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 167 deletions

diff --git a/arch/ia64/include/asm/hw_irq.h b/arch/ia64/include/asm/hw_irq.h
deleted file mode 100644
index 5d267132f8cb..000000000000
--- a/arch/ia64/include/asm/hw_irq.h
+++ /dev/null
@@ -1,167 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _ASM_IA64_HW_IRQ_H
-#define _ASM_IA64_HW_IRQ_H
-
-/*
- * Copyright (C) 2001-2003 Hewlett-Packard Co
- *	David Mosberger-Tang <davidm@hpl.hp.com>
- */
-
-#include <linux/interrupt.h>
-#include <linux/sched.h>
-#include <linux/types.h>
-#include <linux/profile.h>
-
-#include <asm/ptrace.h>
-#include <asm/smp.h>
-
-typedef u8 ia64_vector;
-
-/*
- * 0 special
- *
- * 1,3-14 are reserved from firmware
- *
- * 16-255 (vectored external interrupts) are available
- *
- * 15 spurious interrupt (see IVR)
- *
- * 16 lowest priority, 255 highest priority
- *
- * 15 classes of 16 interrupts each.
- */
-#define IA64_MIN_VECTORED_IRQ		 16
-#define IA64_MAX_VECTORED_IRQ		255
-#define IA64_NUM_VECTORS		256
-
-#define AUTO_ASSIGN			-1
-
-#define IA64_SPURIOUS_INT_VECTOR	0x0f
-
-/*
- * Vectors 0x10-0x1f are used for low priority interrupts, e.g. CMCI.
- */
-#define IA64_CPEP_VECTOR		0x1c	/* corrected platform error polling vector */
-#define IA64_CMCP_VECTOR		0x1d	/* corrected machine-check polling vector */
-#define IA64_CPE_VECTOR			0x1e	/* corrected platform error interrupt vector */
-#define IA64_CMC_VECTOR			0x1f	/* corrected machine-check interrupt vector */
-/*
- * Vectors 0x20-0x2f are reserved for legacy ISA IRQs.
- * Use vectors 0x30-0xe7 as the default device vector range for ia64.
- * Platforms may choose to reduce this range in platform_irq_setup, but the
- * platform range must fall within
- *	[IA64_DEF_FIRST_DEVICE_VECTOR..IA64_DEF_LAST_DEVICE_VECTOR]
- */
-extern int ia64_first_device_vector;
-extern int ia64_last_device_vector;
-
-#ifdef CONFIG_SMP
-/* Reserve the lower priority vector than device vectors for "move IRQ" IPI */
-#define IA64_IRQ_MOVE_VECTOR		0x30	/* "move IRQ" IPI */
-#define IA64_DEF_FIRST_DEVICE_VECTOR	0x31
-#else
-#define IA64_DEF_FIRST_DEVICE_VECTOR	0x30
-#endif
-#define IA64_DEF_LAST_DEVICE_VECTOR	0xe7
-#define IA64_FIRST_DEVICE_VECTOR	ia64_first_device_vector
-#define IA64_LAST_DEVICE_VECTOR		ia64_last_device_vector
-#define IA64_MAX_DEVICE_VECTORS		(IA64_DEF_LAST_DEVICE_VECTOR - IA64_DEF_FIRST_DEVICE_VECTOR + 1)
-#define IA64_NUM_DEVICE_VECTORS		(IA64_LAST_DEVICE_VECTOR - IA64_FIRST_DEVICE_VECTOR + 1)
-
-#define IA64_MCA_RENDEZ_VECTOR		0xe8	/* MCA rendez interrupt */
-#define IA64_TIMER_VECTOR		0xef	/* use highest-prio group 15 interrupt for timer */
-#define	IA64_MCA_WAKEUP_VECTOR		0xf0	/* MCA wakeup (must be >MCA_RENDEZ_VECTOR) */
-#define IA64_IPI_LOCAL_TLB_FLUSH	0xfc	/* SMP flush local TLB */
-#define IA64_IPI_RESCHEDULE		0xfd	/* SMP reschedule */
-#define IA64_IPI_VECTOR			0xfe	/* inter-processor interrupt vector */
-
-/* Used for encoding redirected irqs */
-
-#define IA64_IRQ_REDIRECTED		(1 << 31)
-
-/* IA64 inter-cpu interrupt related definitions */
-
-#define IA64_IPI_DEFAULT_BASE_ADDR	0xfee00000
-
-/* Delivery modes for inter-cpu interrupts */
-enum {
-        IA64_IPI_DM_INT =       0x0,    /* pend an external interrupt */
-        IA64_IPI_DM_PMI =       0x2,    /* pend a PMI */
-        IA64_IPI_DM_NMI =       0x4,    /* pend an NMI (vector 2) */
-        IA64_IPI_DM_INIT =      0x5,    /* pend an INIT interrupt */
-        IA64_IPI_DM_EXTINT =    0x7,    /* pend an 8259-compatible interrupt. */
-};
-
-extern __u8 isa_irq_to_vector_map[16];
-#define isa_irq_to_vector(x)	isa_irq_to_vector_map[(x)]
-
-struct irq_cfg {
-	ia64_vector vector;
-	cpumask_t domain;
-	cpumask_t old_domain;
-	unsigned move_cleanup_count;
-	u8 move_in_progress : 1;
-};
-extern spinlock_t vector_lock;
-extern struct irq_cfg irq_cfg[NR_IRQS];
-#define irq_to_domain(x)	irq_cfg[(x)].domain
-DECLARE_PER_CPU(int[IA64_NUM_VECTORS], vector_irq);
-
-extern struct irq_chip irq_type_ia64_lsapic;	/* CPU-internal interrupt controller */
-
-#define ia64_register_ipi	ia64_native_register_ipi
-#define assign_irq_vector	ia64_native_assign_irq_vector
-#define free_irq_vector		ia64_native_free_irq_vector
-#define ia64_resend_irq		ia64_native_resend_irq
-
-extern void ia64_native_register_ipi(void);
-extern int bind_irq_vector(int irq, int vector, cpumask_t domain);
-extern int ia64_native_assign_irq_vector (int irq);	/* allocate a free vector */
-extern void ia64_native_free_irq_vector (int vector);
-extern int reserve_irq_vector (int vector);
-extern void __setup_vector_irq(int cpu);
-extern void ia64_send_ipi (int cpu, int vector, int delivery_mode, int redirect);
-extern void destroy_and_reserve_irq (unsigned int irq);
-
-#ifdef CONFIG_SMP
-extern int irq_prepare_move(int irq, int cpu);
-extern void irq_complete_move(unsigned int irq);
-#else
-static inline int irq_prepare_move(int irq, int cpu) { return 0; }
-static inline void irq_complete_move(unsigned int irq) {}
-#endif
-
-static inline void ia64_native_resend_irq(unsigned int vector)
-{
-	ia64_send_ipi(smp_processor_id(), vector, IA64_IPI_DM_INT, 0);
-}
-
-/*
- * Next follows the irq descriptor interface.  On IA-64, each CPU supports 256 interrupt
- * vectors.  On smaller systems, there is a one-to-one correspondence between interrupt
- * vectors and the Linux irq numbers.  However, larger systems may have multiple interrupt
- * domains meaning that the translation from vector number to irq number depends on the
- * interrupt domain that a CPU belongs to.  This API abstracts such platform-dependent
- * differences and provides a uniform means to translate between vector and irq numbers
- * and to obtain the irq descriptor for a given irq number.
- */
-
-/* Extract the IA-64 vector that corresponds to IRQ.  */
-static inline ia64_vector
-irq_to_vector (int irq)
-{
-	return irq_cfg[irq].vector;
-}
-
-/*
- * Convert the local IA-64 vector to the corresponding irq number.  This translation is
- * done in the context of the interrupt domain that the currently executing CPU belongs
- * to.
- */
-static inline unsigned int
-local_vector_to_irq (ia64_vector vec)
-{
-	return __this_cpu_read(vector_irq[vec]);
-}
-
-#endif /* _ASM_IA64_HW_IRQ_H */