ARC: [plat-eznps] handle extra aux regs #1: save/restore on context switch

save EFLAGS, and GPA1 auxiliary registers during context switch,
since they may be changed by the new task in kernel mode, while using atomic
ops e.g. cmpxchg.
Signed-off-by: Noam Camus <noamc@ezchip.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/include/asm/processor.h

@@ -27,6 +27,13 @@ struct arc_fpu {
 };
 #endif
 
+#ifdef CONFIG_ARC_PLAT_EZNPS
+struct eznps_dp {
+	unsigned int eflags;
+	unsigned int gpa1;
+};
+#endif
+
 /* Arch specific stuff which needs to be saved per task.
  * However these items are not so important so as to earn a place in
  * struct thread_info
@@ -38,6 +45,9 @@ struct thread_struct {
 #ifdef CONFIG_ARC_FPU_SAVE_RESTORE
 	struct arc_fpu fpu;
 #endif
+#ifdef CONFIG_ARC_PLAT_EZNPS
+	struct eznps_dp dp;
+#endif
 };
 
 #define INIT_THREAD  {                          \

arch/arc/include/asm/switch_to.h

@@ -26,10 +26,19 @@ extern void fpu_save_restore(struct task_struct *p, struct task_struct *n);
 
 #endif /* !CONFIG_ARC_FPU_SAVE_RESTORE */
 
+#ifdef CONFIG_ARC_PLAT_EZNPS
+extern void dp_save_restore(struct task_struct *p, struct task_struct *n);
+#define ARC_EZNPS_DP_PREV(p, n)      dp_save_restore(p, n)
+#else
+#define ARC_EZNPS_DP_PREV(p, n)
+
+#endif /* !CONFIG_ARC_PLAT_EZNPS */
+
 struct task_struct *__switch_to(struct task_struct *p, struct task_struct *n);
 
 #define switch_to(prev, next, last)	\
 do {					\
+	ARC_EZNPS_DP_PREV(prev, next);	\
 	ARC_FPU_PREV(prev, next);	\
 	last = __switch_to(prev, next);\
 	ARC_FPU_NEXT(next);		\

arch/arc/plat-eznps/Makefile

@@ -2,6 +2,6 @@
 # Makefile for the linux kernel.
 #
 
-obj-y := entry.o platform.o
+obj-y := entry.o platform.o ctop.o
 obj-$(CONFIG_SMP) += smp.o
 obj-$(CONFIG_EZNPS_MTM_EXT) += mtm.o

arch/arc/plat-eznps/ctop.c

+/*
+ * Copyright(c) 2015 EZchip Technologies.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * The full GNU General Public License is included in this distribution in
+ * the file called "COPYING".
+ */
+
+#include <linux/sched.h>
+#include <asm/processor.h>
+#include <plat/ctop.h>
+
+void dp_save_restore(struct task_struct *prev, struct task_struct *next)
+{
+	struct eznps_dp *prev_task_dp = &prev->thread.dp;
+	struct eznps_dp *next_task_dp = &next->thread.dp;
+
+	/* Here we save all Data Plane related auxiliary registers */
+	prev_task_dp->eflags = read_aux_reg(CTOP_AUX_EFLAGS);
+	write_aux_reg(CTOP_AUX_EFLAGS, next_task_dp->eflags);
+
+	prev_task_dp->gpa1 = read_aux_reg(CTOP_AUX_GPA1);
+	write_aux_reg(CTOP_AUX_GPA1, next_task_dp->gpa1);
+}