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[PATCH V3 7/8] MIPS: Loongson-3: Enable the COP2 usage

To: Ralf Baechle <ralf@linux-mips.org>
Subject: [PATCH V3 7/8] MIPS: Loongson-3: Enable the COP2 usage
From: Huacai Chen <chenhc@lemote.com>
Date: Thu, 26 Jun 2014 11:41:31 +0800
Cc: John Crispin <john@phrozen.org>, "Steven J. Hill" <Steven.Hill@imgtec.com>, Aurelien Jarno <aurelien@aurel32.net>, linux-mips@linux-mips.org, Fuxin Zhang <zhangfx@lemote.com>, Zhangjin Wu <wuzhangjin@gmail.com>, Huacai Chen <chenhc@lemote.com>
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Loongson-3 has some specific instructions (MMI/SIMD) in coprocessor 2.
COP2 isn't independent because it share COP1 (FPU)'s registers. This
patch enable the COP2 usage so user-space programs can use the MMI/SIMD
instructions. When COP2 exception happens, we enable both COP1 (FPU)
and COP2, only in this way the fp context can be saved and restored
correctly.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
---
 arch/mips/include/asm/cop2.h            |    8 ++++
 arch/mips/loongson/loongson-3/Makefile  |    2 +-
 arch/mips/loongson/loongson-3/cop2-ex.c |   63 +++++++++++++++++++++++++++++++
 3 files changed, 72 insertions(+), 1 deletions(-)
 create mode 100644 arch/mips/loongson/loongson-3/cop2-ex.c

diff --git a/arch/mips/include/asm/cop2.h b/arch/mips/include/asm/cop2.h
index c1516cc..d035298 100644
--- a/arch/mips/include/asm/cop2.h
+++ b/arch/mips/include/asm/cop2.h
@@ -32,6 +32,14 @@ extern void nlm_cop2_restore(struct nlm_cop2_state *);
 #define cop2_present           1
 #define cop2_lazy_restore      0
 
+#elif defined(CONFIG_CPU_LOONGSON3)
+
+#define cop2_save(r)
+#define cop2_restore(r)
+
+#define cop2_present           1
+#define cop2_lazy_restore      1
+
 #else
 
 #define cop2_present           0
diff --git a/arch/mips/loongson/loongson-3/Makefile 
b/arch/mips/loongson/loongson-3/Makefile
index 471b0f2a..b4df775 100644
--- a/arch/mips/loongson/loongson-3/Makefile
+++ b/arch/mips/loongson/loongson-3/Makefile
@@ -1,7 +1,7 @@
 #
 # Makefile for Loongson-3 family machines
 #
-obj-y                  += irq.o
+obj-y                  += irq.o cop2-ex.o
 
 obj-$(CONFIG_SMP)      += smp.o
 
diff --git a/arch/mips/loongson/loongson-3/cop2-ex.c 
b/arch/mips/loongson/loongson-3/cop2-ex.c
new file mode 100644
index 0000000..9182e8d
--- /dev/null
+++ b/arch/mips/loongson/loongson-3/cop2-ex.c
@@ -0,0 +1,63 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2014 Lemote Corporation.
+ *   written by Huacai Chen <chenhc@lemote.com>
+ *
+ * based on arch/mips/cavium-octeon/cpu.c
+ * Copyright (C) 2009 Wind River Systems,
+ *   written by Ralf Baechle <ralf@linux-mips.org>
+ */
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/notifier.h>
+
+#include <asm/fpu.h>
+#include <asm/cop2.h>
+#include <asm/current.h>
+#include <asm/mipsregs.h>
+
+static int loongson_cu2_call(struct notifier_block *nfb, unsigned long action,
+       void *data)
+{
+       int fpu_enabled;
+       int fr = !test_thread_flag(TIF_32BIT_FPREGS);
+
+       switch (action) {
+       case CU2_EXCEPTION:
+               preempt_disable();
+               fpu_enabled = read_c0_status() & ST0_CU1;
+               if (!fr)
+                       set_c0_status(ST0_CU1 | ST0_CU2);
+               else
+                       set_c0_status(ST0_CU1 | ST0_CU2 | ST0_FR);
+               enable_fpu_hazard();
+               KSTK_STATUS(current) |= (ST0_CU1 | ST0_CU2);
+               if (fr)
+                       KSTK_STATUS(current) |= ST0_FR;
+               else
+                       KSTK_STATUS(current) &= ~ST0_FR;
+               /* If FPU is enabled, we needn't init or restore fp */
+               if(!fpu_enabled) {
+                       set_thread_flag(TIF_USEDFPU);
+                       if (!used_math()) {
+                               _init_fpu();
+                               set_used_math();
+                       } else
+                               _restore_fp(current);
+               }
+               preempt_enable();
+
+               return NOTIFY_STOP;     /* Don't call default notifier */
+       }
+
+       return NOTIFY_OK;               /* Let default notifier send signals */
+}
+
+static int __init loongson_cu2_setup(void)
+{
+       return cu2_notifier(loongson_cu2_call, 0);
+}
+early_initcall(loongson_cu2_setup);
-- 
1.7.7.3


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