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, 114 insertions, 0 deletions

diff --git a/arch/nds32/include/asm/fpu.h b/arch/nds32/include/asm/fpu.h
new file mode 100644
index 000000000000..f7a7f6b2ea8f
--- /dev/null
+++ b/arch/nds32/include/asm/fpu.h
@@ -0,0 +1,114 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2005-2018 Andes Technology Corporation */
+
+#ifndef __ASM_NDS32_FPU_H
+#define __ASM_NDS32_FPU_H
+
+#if IS_ENABLED(CONFIG_FPU)
+#ifndef __ASSEMBLY__
+#include <linux/sched/task_stack.h>
+#include <linux/preempt.h>
+#include <asm/ptrace.h>
+
+extern bool has_fpu;
+
+extern void save_fpu(struct task_struct *__tsk);
+extern void load_fpu(const struct fpu_struct *fpregs);
+extern bool do_fpu_exception(unsigned int subtype, struct pt_regs *regs);
+
+#define test_tsk_fpu(regs)	(regs->fucop_ctl & FUCOP_CTL_mskCP0EN)
+
+/*
+ * Initially load the FPU with signalling NANS.  This bit pattern
+ * has the property that no matter whether considered as single or as
+ * double precision, it still represents a signalling NAN.
+ */
+
+#define sNAN64    0xFFFFFFFFFFFFFFFFULL
+#define sNAN32    0xFFFFFFFFUL
+
+#define FPCSR_INIT  0x0UL
+
+extern const struct fpu_struct init_fpuregs;
+
+static inline void disable_ptreg_fpu(struct pt_regs *regs)
+{
+	regs->fucop_ctl &= ~FUCOP_CTL_mskCP0EN;
+}
+
+static inline void enable_ptreg_fpu(struct pt_regs *regs)
+{
+	regs->fucop_ctl |= FUCOP_CTL_mskCP0EN;
+}
+
+static inline void enable_fpu(void)
+{
+	unsigned long fucop_ctl;
+
+	fucop_ctl = __nds32__mfsr(NDS32_SR_FUCOP_CTL) | FUCOP_CTL_mskCP0EN;
+	__nds32__mtsr(fucop_ctl, NDS32_SR_FUCOP_CTL);
+	__nds32__isb();
+}
+
+static inline void disable_fpu(void)
+{
+	unsigned long fucop_ctl;
+
+	fucop_ctl = __nds32__mfsr(NDS32_SR_FUCOP_CTL) & ~FUCOP_CTL_mskCP0EN;
+	__nds32__mtsr(fucop_ctl, NDS32_SR_FUCOP_CTL);
+	__nds32__isb();
+}
+
+static inline void lose_fpu(void)
+{
+	preempt_disable();
+#if IS_ENABLED(CONFIG_LAZY_FPU)
+	if (last_task_used_math == current) {
+		last_task_used_math = NULL;
+#else
+	if (test_tsk_fpu(task_pt_regs(current))) {
+#endif
+		save_fpu(current);
+	}
+	disable_ptreg_fpu(task_pt_regs(current));
+	preempt_enable();
+}
+
+static inline void own_fpu(void)
+{
+	preempt_disable();
+#if IS_ENABLED(CONFIG_LAZY_FPU)
+	if (last_task_used_math != current) {
+		if (last_task_used_math != NULL)
+			save_fpu(last_task_used_math);
+		load_fpu(&current->thread.fpu);
+		last_task_used_math = current;
+	}
+#else
+	if (!test_tsk_fpu(task_pt_regs(current))) {
+		load_fpu(&current->thread.fpu);
+	}
+#endif
+	enable_ptreg_fpu(task_pt_regs(current));
+	preempt_enable();
+}
+
+#if !IS_ENABLED(CONFIG_LAZY_FPU)
+static inline void unlazy_fpu(struct task_struct *tsk)
+{
+	preempt_disable();
+	if (test_tsk_fpu(task_pt_regs(tsk)))
+		save_fpu(tsk);
+	preempt_enable();
+}
+#endif /* !CONFIG_LAZY_FPU */
+static inline void clear_fpu(struct pt_regs *regs)
+{
+	preempt_disable();
+	if (test_tsk_fpu(regs))
+		disable_ptreg_fpu(regs);
+	preempt_enable();
+}
+#endif /* CONFIG_FPU */
+#endif /* __ASSEMBLY__ */
+#endif /* __ASM_NDS32_FPU_H */