Commit f1df3239 authored Mar 13, 2010 by Wu Zhangjin Committed by Ralf Baechle Apr 12, 2010

MIPS: Loongson-2F: Flush the branch target history in BTB and RAS

As per chapter 15 "Errata: Issue of Out-of-order in loongson"[1] to work
around the Loongson 2F erratum we need to do:

"When switching from user mode to kernel mode, you should flush the
branch target history such as BTB and RAS."

[1] Chinese version: http://www.loongson.cn/uploadfile/file/200808211
[2] English version of chapter 15:
    http://groups.google.com.hk/group/loongson-dev/msg/e0d2e220958f10a6?dmode=source



Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Shinya Kuribayashi <shinya.kuribayashi@necel.com>
Patchwork: http://patchwork.linux-mips.org/patch/1066/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

parent d814c28c

arch/mips/include/asm/stackframe.h

+19 −0

Original line number	Diff line number	Diff line
		@@ -121,6 +121,25 @@
		.endm
		#else
		.macro get_saved_sp /* Uniprocessor variation */
		#ifdef CONFIG_CPU_LOONGSON2F
		/*
		* Clear BTB (branch target buffer), forbid RAS (return address
		* stack) to workaround the Out-of-order Issue in Loongson2F
		* via its diagnostic register.
		*/
		move k0, ra
		jal 1f
		nop
		1: jal 1f
		nop
		1: jal 1f
		nop
		1: jal 1f
		nop
		1: move ra, k0
		li k0, 3
		mtc0 k0, $22
		#endif /* CONFIG_CPU_LOONGSON2F */
		#if defined(CONFIG_32BIT) \|\| defined(KBUILD_64BIT_SYM32)
		lui k1, %hi(kernelsp)
		#else