--- zzzz-none-000/linux-3.10.107/arch/mips/include/asm/switch_to.h	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/arch/mips/include/asm/switch_to.h	2021-02-04 17:41:59.000000000 +0000
@@ -15,14 +15,22 @@
 #include <asm/cpu-features.h>
 #include <asm/watch.h>
 #include <asm/dsp.h>
+#include <asm/cop2.h>
+#include <asm/fpu.h>
 
 struct task_struct;
 
-/*
- * switch_to(n) should switch tasks to task nr n, first
- * checking that n isn't the current task, in which case it does nothing.
+/**
+ * resume - resume execution of a task
+ * @prev:	The task previously executed.
+ * @next:	The task to begin executing.
+ * @next_ti:	task_thread_info(next).
+ *
+ * This function is used whilst scheduling to save the context of prev & load
+ * the context of next. Returns prev.
  */
-extern asmlinkage void *resume(void *last, void *next, void *next_ti, u32 __usedfpu);
+extern asmlinkage struct task_struct *resume(struct task_struct *prev,
+		struct task_struct *next, struct thread_info *next_ti);
 
 extern unsigned int ll_bit;
 extern struct task_struct *ll_task;
@@ -59,29 +67,46 @@
 #endif
 
 #define __clear_software_ll_bit()					\
-do {									\
-	if (!__builtin_constant_p(cpu_has_llsc) || !cpu_has_llsc)	\
-		ll_bit = 0;						\
+do {	if (cpu_has_rw_llb) {						\
+		write_c0_lladdr(0);					\
+	} else {							\
+		if (!__builtin_constant_p(cpu_has_llsc) || !cpu_has_llsc)\
+			ll_bit = 0;					\
+	}								\
 } while (0)
 
+/*
+ * For newly created kernel threads switch_to() will return to
+ * ret_from_kernel_thread, newly created user threads to ret_from_fork.
+ * That is, everything following resume() will be skipped for new threads.
+ * So everything that matters to new threads should be placed before resume().
+ */
 #define switch_to(prev, next, last)					\
 do {									\
-	u32 __usedfpu;							\
 	__mips_mt_fpaff_switch_to(prev);				\
-	if (cpu_has_dsp)						\
+	lose_fpu_inatomic(1, prev);					\
+	if (cpu_has_dsp) {						\
 		__save_dsp(prev);					\
+		__restore_dsp(next);					\
+	}								\
+	if (cop2_present) {						\
+		set_c0_status(ST0_CU2);					\
+		if ((KSTK_STATUS(prev) & ST0_CU2)) {			\
+			if (cop2_lazy_restore)				\
+				KSTK_STATUS(prev) &= ~ST0_CU2;		\
+			cop2_save(prev);				\
+		}							\
+		if (KSTK_STATUS(next) & ST0_CU2 &&			\
+		    !cop2_lazy_restore) {				\
+			cop2_restore(next);				\
+		}							\
+		clear_c0_status(ST0_CU2);				\
+	}								\
 	__clear_software_ll_bit();					\
-	__usedfpu = test_and_clear_tsk_thread_flag(prev, TIF_USEDFPU);	\
-	(last) = resume(prev, next, task_thread_info(next), __usedfpu); \
-} while (0)
-
-#define finish_arch_switch(prev)					\
-do {									\
-	if (cpu_has_dsp)						\
-		__restore_dsp(current);					\
 	if (cpu_has_userlocal)						\
-		write_c0_userlocal(current_thread_info()->tp_value);	\
-	__restore_watch();						\
+		write_c0_userlocal(task_thread_info(next)->tp_value);	\
+	__restore_watch(next);						\
+	(last) = resume(prev, next, task_thread_info(next));		\
 } while (0)
 
 #endif /* _ASM_SWITCH_TO_H */