nds32: Remove the architecture

The nds32 architecture, also known as AndeStar V3, is a custom 32-bit
RISC target designed by Andes Technologies. Support was added to the
kernel in 2016 as the replacement RISC-V based V5 processors were
already announced, and maintained by (current or former) Andes
employees.

As explained by Alan Kao, new customers are now all using RISC-V,
and all known nds32 users are already on longterm stable kernels
provided by Andes, with no development work going into mainline
support any more.

While the port is still in a reasonably good shape, it only gets
worse over time without active maintainers, so it seems best
to remove it before it becomes unusable. As always, if it turns
out that there are mainline users after all, and they volunteer
to maintain the port in the future, the removal can be reverted.

Link: https://lore.kernel.org/linux-mm/YhdWNLUhk+x9RAzU@yamatobi.andestech.com/
Link: https://lore.kernel.org/lkml/20220302065213.82702-1-alankao@andestech.com/
Link: https://www.andestech.com/en/products-solutions/andestar-architecture/
Signed-off-by: Alan Kao <alankao@andestech.com>
[arnd: rewrite changelog to provide more background]
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 0 insertions, 266 deletions

diff --git a/arch/nds32/kernel/fpu.c b/arch/nds32/kernel/fpu.c
deleted file mode 100644
index 701c09a668de..000000000000
--- a/arch/nds32/kernel/fpu.c
+++ /dev/null
@@ -1,266 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-// Copyright (C) 2005-2018 Andes Technology Corporation
-
-#include <linux/sched.h>
-#include <linux/signal.h>
-#include <linux/sched/signal.h>
-#include <asm/processor.h>
-#include <asm/user.h>
-#include <asm/io.h>
-#include <asm/bitfield.h>
-#include <asm/fpu.h>
-
-const struct fpu_struct init_fpuregs = {
-	.fd_regs = {[0 ... 31] = sNAN64},
-	.fpcsr = FPCSR_INIT,
-#if IS_ENABLED(CONFIG_SUPPORT_DENORMAL_ARITHMETIC)
-	.UDF_IEX_trap = 0
-#endif
-};
-
-void save_fpu(struct task_struct *tsk)
-{
-	unsigned int fpcfg, fpcsr;
-
-	enable_fpu();
-	fpcfg = ((__nds32__fmfcfg() & FPCFG_mskFREG) >> FPCFG_offFREG);
-	switch (fpcfg) {
-	case SP32_DP32_reg:
-		asm volatile ("fsdi $fd31, [%0+0xf8]\n\t"
-			      "fsdi $fd30, [%0+0xf0]\n\t"
-			      "fsdi $fd29, [%0+0xe8]\n\t"
-			      "fsdi $fd28, [%0+0xe0]\n\t"
-			      "fsdi $fd27, [%0+0xd8]\n\t"
-			      "fsdi $fd26, [%0+0xd0]\n\t"
-			      "fsdi $fd25, [%0+0xc8]\n\t"
-			      "fsdi $fd24, [%0+0xc0]\n\t"
-			      "fsdi $fd23, [%0+0xb8]\n\t"
-			      "fsdi $fd22, [%0+0xb0]\n\t"
-			      "fsdi $fd21, [%0+0xa8]\n\t"
-			      "fsdi $fd20, [%0+0xa0]\n\t"
-			      "fsdi $fd19, [%0+0x98]\n\t"
-			      "fsdi $fd18, [%0+0x90]\n\t"
-			      "fsdi $fd17, [%0+0x88]\n\t"
-			      "fsdi $fd16, [%0+0x80]\n\t"
-			      :	/* no output */
-			      : "r" (&tsk->thread.fpu)
-			      : "memory");
-		fallthrough;
-	case SP32_DP16_reg:
-		asm volatile ("fsdi $fd15, [%0+0x78]\n\t"
-			      "fsdi $fd14, [%0+0x70]\n\t"
-			      "fsdi $fd13, [%0+0x68]\n\t"
-			      "fsdi $fd12, [%0+0x60]\n\t"
-			      "fsdi $fd11, [%0+0x58]\n\t"
-			      "fsdi $fd10, [%0+0x50]\n\t"
-			      "fsdi $fd9,  [%0+0x48]\n\t"
-			      "fsdi $fd8,  [%0+0x40]\n\t"
-			      :	/* no output */
-			      : "r" (&tsk->thread.fpu)
-			      : "memory");
-		fallthrough;
-	case SP16_DP8_reg:
-		asm volatile ("fsdi $fd7,  [%0+0x38]\n\t"
-			      "fsdi $fd6,  [%0+0x30]\n\t"
-			      "fsdi $fd5,  [%0+0x28]\n\t"
-			      "fsdi $fd4,  [%0+0x20]\n\t"
-			      :	/* no output */
-			      : "r" (&tsk->thread.fpu)
-			      : "memory");
-		fallthrough;
-	case SP8_DP4_reg:
-		asm volatile ("fsdi $fd3,  [%1+0x18]\n\t"
-			      "fsdi $fd2,  [%1+0x10]\n\t"
-			      "fsdi $fd1,  [%1+0x8]\n\t"
-			      "fsdi $fd0,  [%1+0x0]\n\t"
-			      "fmfcsr	%0\n\t"
-			      "swi  %0, [%1+0x100]\n\t"
-			      : "=&r" (fpcsr)
-			      : "r"(&tsk->thread.fpu)
-			      : "memory");
-	}
-	disable_fpu();
-}
-
-void load_fpu(const struct fpu_struct *fpregs)
-{
-	unsigned int fpcfg, fpcsr;
-
-	enable_fpu();
-	fpcfg = ((__nds32__fmfcfg() & FPCFG_mskFREG) >> FPCFG_offFREG);
-	switch (fpcfg) {
-	case SP32_DP32_reg:
-		asm volatile ("fldi $fd31, [%0+0xf8]\n\t"
-			      "fldi $fd30, [%0+0xf0]\n\t"
-			      "fldi $fd29, [%0+0xe8]\n\t"
-			      "fldi $fd28, [%0+0xe0]\n\t"
-			      "fldi $fd27, [%0+0xd8]\n\t"
-			      "fldi $fd26, [%0+0xd0]\n\t"
-			      "fldi $fd25, [%0+0xc8]\n\t"
-			      "fldi $fd24, [%0+0xc0]\n\t"
-			      "fldi $fd23, [%0+0xb8]\n\t"
-			      "fldi $fd22, [%0+0xb0]\n\t"
-			      "fldi $fd21, [%0+0xa8]\n\t"
-			      "fldi $fd20, [%0+0xa0]\n\t"
-			      "fldi $fd19, [%0+0x98]\n\t"
-			      "fldi $fd18, [%0+0x90]\n\t"
-			      "fldi $fd17, [%0+0x88]\n\t"
-			      "fldi $fd16, [%0+0x80]\n\t"
-			      :	/* no output */
-			      : "r" (fpregs));
-		fallthrough;
-	case SP32_DP16_reg:
-		asm volatile ("fldi $fd15, [%0+0x78]\n\t"
-			      "fldi $fd14, [%0+0x70]\n\t"
-			      "fldi $fd13, [%0+0x68]\n\t"
-			      "fldi $fd12, [%0+0x60]\n\t"
-			      "fldi $fd11, [%0+0x58]\n\t"
-			      "fldi $fd10, [%0+0x50]\n\t"
-			      "fldi $fd9,  [%0+0x48]\n\t"
-			      "fldi $fd8,  [%0+0x40]\n\t"
-			      :	/* no output */
-			      : "r" (fpregs));
-		fallthrough;
-	case SP16_DP8_reg:
-		asm volatile ("fldi $fd7,  [%0+0x38]\n\t"
-			      "fldi $fd6,  [%0+0x30]\n\t"
-			      "fldi $fd5,  [%0+0x28]\n\t"
-			      "fldi $fd4,  [%0+0x20]\n\t"
-			      :	/* no output */
-			      : "r" (fpregs));
-		fallthrough;
-	case SP8_DP4_reg:
-		asm volatile ("fldi $fd3,  [%1+0x18]\n\t"
-			      "fldi $fd2,  [%1+0x10]\n\t"
-			      "fldi $fd1,  [%1+0x8]\n\t"
-			      "fldi $fd0,  [%1+0x0]\n\t"
-			      "lwi  %0, [%1+0x100]\n\t"
-			      "fmtcsr	%0\n\t":"=&r" (fpcsr)
-			      : "r"(fpregs));
-	}
-	disable_fpu();
-}
-void store_fpu_for_suspend(void)
-{
-#ifdef CONFIG_LAZY_FPU
-	if (last_task_used_math != NULL)
-		save_fpu(last_task_used_math);
-	last_task_used_math = NULL;
-#else
-	if (!used_math())
-		return;
-	unlazy_fpu(current);
-#endif
-	clear_fpu(task_pt_regs(current));
-}
-inline void do_fpu_context_switch(struct pt_regs *regs)
-{
-	/* Enable to use FPU. */
-
-	if (!user_mode(regs)) {
-		pr_err("BUG: FPU is used in kernel mode.\n");
-		BUG();
-		return;
-	}
-
-	enable_ptreg_fpu(regs);
-#ifdef CONFIG_LAZY_FPU	//Lazy FPU is used
-	if (last_task_used_math == current)
-		return;
-	if (last_task_used_math != NULL)
-		/* Other processes fpu state, save away */
-		save_fpu(last_task_used_math);
-	last_task_used_math = current;
-#endif
-	if (used_math()) {
-		load_fpu(&current->thread.fpu);
-	} else {
-		/* First time FPU user.  */
-		load_fpu(&init_fpuregs);
-#if IS_ENABLED(CONFIG_SUPPORT_DENORMAL_ARITHMETIC)
-		current->thread.fpu.UDF_IEX_trap = init_fpuregs.UDF_IEX_trap;
-#endif
-		set_used_math();
-	}
-
-}
-
-inline void fill_sigfpe_signo(unsigned int fpcsr, int *signo)
-{
-	if (fpcsr & FPCSR_mskOVFT)
-		*signo = FPE_FLTOVF;
-#ifndef CONFIG_SUPPORT_DENORMAL_ARITHMETIC
-	else if (fpcsr & FPCSR_mskUDFT)
-		*signo = FPE_FLTUND;
-#endif
-	else if (fpcsr & FPCSR_mskIVOT)
-		*signo = FPE_FLTINV;
-	else if (fpcsr & FPCSR_mskDBZT)
-		*signo = FPE_FLTDIV;
-	else if (fpcsr & FPCSR_mskIEXT)
-		*signo = FPE_FLTRES;
-}
-
-inline void handle_fpu_exception(struct pt_regs *regs)
-{
-	unsigned int fpcsr;
-	int si_code = 0, si_signo = SIGFPE;
-#if IS_ENABLED(CONFIG_SUPPORT_DENORMAL_ARITHMETIC)
-	unsigned long redo_except = FPCSR_mskDNIT|FPCSR_mskUDFT|FPCSR_mskIEXT;
-#else
-	unsigned long redo_except = FPCSR_mskDNIT;
-#endif
-
-	lose_fpu();
-	fpcsr = current->thread.fpu.fpcsr;
-
-	if (fpcsr & redo_except) {
-		si_signo = do_fpuemu(regs, &current->thread.fpu);
-		fpcsr = current->thread.fpu.fpcsr;
-		if (!si_signo) {
-			current->thread.fpu.fpcsr &= ~(redo_except);
-			goto done;
-		}
-	} else if (fpcsr & FPCSR_mskRIT) {
-		if (!user_mode(regs))
-			make_task_dead(SIGILL);
-		si_signo = SIGILL;
-	}
-
-	switch (si_signo) {
-	case SIGFPE:
-		fill_sigfpe_signo(fpcsr, &si_code);
-		break;
-	case SIGILL:
-		show_regs(regs);
-		si_code = ILL_COPROC;
-		break;
-	case SIGBUS:
-		si_code = BUS_ADRERR;
-		break;
-	default:
-		break;
-	}
-
-	force_sig_fault(si_signo, si_code,
-			(void __user *)instruction_pointer(regs));
-done:
-	own_fpu();
-}
-
-bool do_fpu_exception(unsigned int subtype, struct pt_regs *regs)
-{
-	int done = true;
-	/* Coprocessor disabled exception */
-	if (subtype == FPU_DISABLE_EXCEPTION) {
-		preempt_disable();
-		do_fpu_context_switch(regs);
-		preempt_enable();
-	}
-	/* Coprocessor exception such as underflow and overflow */
-	else if (subtype == FPU_EXCEPTION)
-		handle_fpu_exception(regs);
-	else
-		done = false;
-	return done;
-}