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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 106 deletions

diff --git a/arch/ia64/include/asm/iosapic.h b/arch/ia64/include/asm/iosapic.h
deleted file mode 100644
index a91aeb413e17..000000000000
--- a/arch/ia64/include/asm/iosapic.h
+++ /dev/null
@@ -1,106 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef __ASM_IA64_IOSAPIC_H
-#define __ASM_IA64_IOSAPIC_H
-
-#define	IOSAPIC_REG_SELECT	0x0
-#define	IOSAPIC_WINDOW		0x10
-#define	IOSAPIC_EOI		0x40
-
-#define	IOSAPIC_VERSION		0x1
-
-/*
- * Redirection table entry
- */
-#define	IOSAPIC_RTE_LOW(i)	(0x10+i*2)
-#define	IOSAPIC_RTE_HIGH(i)	(0x11+i*2)
-
-#define	IOSAPIC_DEST_SHIFT		16
-
-/*
- * Delivery mode
- */
-#define	IOSAPIC_DELIVERY_SHIFT		8
-#define	IOSAPIC_FIXED			0x0
-#define	IOSAPIC_LOWEST_PRIORITY	0x1
-#define	IOSAPIC_PMI			0x2
-#define	IOSAPIC_NMI			0x4
-#define	IOSAPIC_INIT			0x5
-#define	IOSAPIC_EXTINT			0x7
-
-/*
- * Interrupt polarity
- */
-#define	IOSAPIC_POLARITY_SHIFT		13
-#define	IOSAPIC_POL_HIGH		0
-#define	IOSAPIC_POL_LOW		1
-
-/*
- * Trigger mode
- */
-#define	IOSAPIC_TRIGGER_SHIFT		15
-#define	IOSAPIC_EDGE			0
-#define	IOSAPIC_LEVEL			1
-
-/*
- * Mask bit
- */
-
-#define	IOSAPIC_MASK_SHIFT		16
-#define	IOSAPIC_MASK			(1<<IOSAPIC_MASK_SHIFT)
-
-#define IOSAPIC_VECTOR_MASK		0xffffff00
-
-#ifndef __ASSEMBLY__
-
-#define NR_IOSAPICS			256
-
-#define iosapic_pcat_compat_init	ia64_native_iosapic_pcat_compat_init
-#define __iosapic_read			__ia64_native_iosapic_read
-#define __iosapic_write			__ia64_native_iosapic_write
-#define iosapic_get_irq_chip		ia64_native_iosapic_get_irq_chip
-
-extern void __init ia64_native_iosapic_pcat_compat_init(void);
-extern struct irq_chip *ia64_native_iosapic_get_irq_chip(unsigned long trigger);
-
-static inline unsigned int
-__ia64_native_iosapic_read(char __iomem *iosapic, unsigned int reg)
-{
-	writel(reg, iosapic + IOSAPIC_REG_SELECT);
-	return readl(iosapic + IOSAPIC_WINDOW);
-}
-
-static inline void
-__ia64_native_iosapic_write(char __iomem *iosapic, unsigned int reg, u32 val)
-{
-	writel(reg, iosapic + IOSAPIC_REG_SELECT);
-	writel(val, iosapic + IOSAPIC_WINDOW);
-}
-
-static inline void iosapic_eoi(char __iomem *iosapic, u32 vector)
-{
-	writel(vector, iosapic + IOSAPIC_EOI);
-}
-
-extern void __init iosapic_system_init (int pcat_compat);
-extern int iosapic_init (unsigned long address, unsigned int gsi_base);
-extern int iosapic_remove (unsigned int gsi_base);
-extern int gsi_to_irq (unsigned int gsi);
-extern int iosapic_register_intr (unsigned int gsi, unsigned long polarity,
-				  unsigned long trigger);
-extern void iosapic_unregister_intr (unsigned int irq);
-extern void iosapic_override_isa_irq (unsigned int isa_irq, unsigned int gsi,
-				      unsigned long polarity,
-				      unsigned long trigger);
-extern int __init iosapic_register_platform_intr (u32 int_type,
-					   unsigned int gsi,
-					   int pmi_vector,
-					   u16 eid, u16 id,
-					   unsigned long polarity,
-					   unsigned long trigger);
-
-#ifdef CONFIG_NUMA
-extern void map_iosapic_to_node (unsigned int, int);
-#endif
-
-# endif /* !__ASSEMBLY__ */
-#endif /* __ASM_IA64_IOSAPIC_H */