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, 59 insertions, 5 deletions

diff --git a/arch/nds32/kernel/process.c b/arch/nds32/kernel/process.c
index 65fda986e55f..ab7ab46234b1 100644
--- a/arch/nds32/kernel/process.c
+++ b/arch/nds32/kernel/process.c
@@ -9,15 +9,16 @@
 #include <linux/uaccess.h>
 #include <asm/elf.h>
 #include <asm/proc-fns.h>
+#include <asm/fpu.h>
 #include <linux/ptrace.h>
 #include <linux/reboot.h>
 
-extern void setup_mm_for_reboot(char mode);
-#ifdef CONFIG_PROC_FS
-struct proc_dir_entry *proc_dir_cpu;
-EXPORT_SYMBOL(proc_dir_cpu);
+#if IS_ENABLED(CONFIG_LAZY_FPU)
+struct task_struct *last_task_used_math;
 #endif
 
+extern void setup_mm_for_reboot(char mode);
+
 extern inline void arch_reset(char mode)
 {
 	if (mode == 's') {
@@ -125,15 +126,31 @@ void show_regs(struct pt_regs *regs)
 
 EXPORT_SYMBOL(show_regs);
 
+void exit_thread(struct task_struct *tsk)
+{
+#if defined(CONFIG_FPU) && defined(CONFIG_LAZY_FPU)
+	if (last_task_used_math == tsk)
+		last_task_used_math = NULL;
+#endif
+}
+
 void flush_thread(void)
 {
+#if defined(CONFIG_FPU)
+	clear_fpu(task_pt_regs(current));
+	clear_used_math();
+# ifdef CONFIG_LAZY_FPU
+	if (last_task_used_math == current)
+		last_task_used_math = NULL;
+# endif
+#endif
 }
 
 DEFINE_PER_CPU(struct task_struct *, __entry_task);
 
 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
 int copy_thread(unsigned long clone_flags, unsigned long stack_start,
-	    unsigned long stk_sz, struct task_struct *p)
+		unsigned long stk_sz, struct task_struct *p)
 {
 	struct pt_regs *childregs = task_pt_regs(p);
 
@@ -159,6 +176,22 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
 	p->thread.cpu_context.pc = (unsigned long)ret_from_fork;
 	p->thread.cpu_context.sp = (unsigned long)childregs;
 
+#if IS_ENABLED(CONFIG_FPU)
+	if (used_math()) {
+# if !IS_ENABLED(CONFIG_LAZY_FPU)
+		unlazy_fpu(current);
+# else
+		preempt_disable();
+		if (last_task_used_math == current)
+			save_fpu(current);
+		preempt_enable();
+# endif
+		p->thread.fpu = current->thread.fpu;
+		clear_fpu(task_pt_regs(p));
+		set_stopped_child_used_math(p);
+	}
+#endif
+
 #ifdef CONFIG_HWZOL
 	childregs->lb = 0;
 	childregs->le = 0;
@@ -168,12 +201,33 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
 	return 0;
 }
 
+#if IS_ENABLED(CONFIG_FPU)
+struct task_struct *_switch_fpu(struct task_struct *prev, struct task_struct *next)
+{
+#if !IS_ENABLED(CONFIG_LAZY_FPU)
+	unlazy_fpu(prev);
+#endif
+	if (!(next->flags & PF_KTHREAD))
+		clear_fpu(task_pt_regs(next));
+	return prev;
+}
+#endif
+
 /*
  * fill in the fpe structure for a core dump...
  */
 int dump_fpu(struct pt_regs *regs, elf_fpregset_t * fpu)
 {
 	int fpvalid = 0;
+#if IS_ENABLED(CONFIG_FPU)
+	struct task_struct *tsk = current;
+
+	fpvalid = tsk_used_math(tsk);
+	if (fpvalid) {
+		lose_fpu();
+		memcpy(fpu, &tsk->thread.fpu, sizeof(*fpu));
+	}
+#endif
 	return fpvalid;
 }