nds32: nds32 FPU port

This patch set contains basic components for supporting the nds32 FPU,
such as exception handlers and context switch for FPU registers. By
default, the lazy FPU scheme is supported and the user can configure it via
CONFIG_LZAY_FPU.

Signed-off-by: Vincent Chen <vincentc@andestech.com>
Acked-by: Greentime Hu <greentime@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>

1 files changed, 231 insertions, 0 deletions

diff --git a/arch/nds32/kernel/fpu.c b/arch/nds32/kernel/fpu.c
new file mode 100644
index 000000000000..e55a1e190e97
--- /dev/null
+++ b/arch/nds32/kernel/fpu.c
@@ -0,0 +1,231 @@
+// 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
+};
+
+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");
+		/* fall through */
+	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");
+		/* fall through */
+	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");
+		/* fall through */
+	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));
+		/* fall through */
+	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));
+		/* fall through */
+	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));
+		/* fall through */
+	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);
+		set_used_math();
+	}
+
+}
+
+inline void fill_sigfpe_signo(unsigned int fpcsr, int *signo)
+{
+	if (fpcsr & FPCSR_mskOVFT)
+		*signo = FPE_FLTOVF;
+	else if (fpcsr & FPCSR_mskUDFT)
+		*signo = FPE_FLTUND;
+	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;
+
+	lose_fpu();
+	fpcsr = current->thread.fpu.fpcsr;
+
+	if (fpcsr & FPCSR_mskRIT) {
+		if (!user_mode(regs))
+			do_exit(SIGILL);
+		si_signo = SIGILL;
+		show_regs(regs);
+		si_code = ILL_COPROC;
+	} else
+		fill_sigfpe_signo(fpcsr, &si_code);
+	force_sig_fault(si_signo, si_code,
+			(void __user *)instruction_pointer(regs), current);
+}
+
+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;
+}