linux-mips
[Top] [All Lists]

[PATCH v2 1/3] Loongson-2F: Flush the branch target history such as BTB

To: Ralf Baechle <ralf@linux-mips.org>
Subject: [PATCH v2 1/3] Loongson-2F: Flush the branch target history such as BTB and RAS
From: Wu Zhangjin <wuzhangjin@gmail.com>
Date: Thu, 11 Mar 2010 11:05:02 +0800
Cc: linux-mips@linux-mips.org, Sergei Shtylyov <sshtylyov@mvista.com>, Wu Zhangjin <wuzhangjin@gmail.com>
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:from:to:cc:subject:date :message-id:x-mailer:in-reply-to:references:in-reply-to:references :mime-version:content-type:content-transfer-encoding; bh=Op90jrXvfNgeLyTOb7jEkgGfxp0RHsZl8xhaeMbPWoQ=; b=RcyuveuyVyT1psbDRkDsjq1g0IJM92exyFTKgyoN5n5xVUi16twFRhSkIwXYfpLxic F2ol9OzKeB9dM1xdezJL/y1RjeuqgKVrRaSJ1UiScqT19JJz5PovG+rE0YW4dJjgq0W+ 7ltz6rhQwZuSUPpQFS9sk+buM4DJ+7QrwZyMs=
Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references :mime-version:content-type:content-transfer-encoding; b=JTBp13OaVmPQ4c+nGX8zZjqaJOkD2q3xHg41sYWWcGWKP7RFLOVQ1hNG/KsRN9QCJy zEv/2vJZdLPqph/1TtgqSfkMzVFpMRrtN4+n09xNrZvKtC4GiZWDyj5w/5u21CXQDlW+ n8VmCg/E3+uzvIRMM+7YLeObgBpFHdMIodbsI=
In-reply-to: <cover.1268276417.git.wuzhangjin@gmail.com>
In-reply-to: <cover.1268276417.git.wuzhangjin@gmail.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <cover.1268276417.git.wuzhangjin@gmail.com>
References: <cover.1268276417.git.wuzhangjin@gmail.com>
Sender: linux-mips-bounce@linux-mips.org
From: Wu Zhangjin <wuzhangjin@gmail.com>

As the Chapter 15: "Errata: Issue of Out-of-order in loongson"[1] shows, to
workaround the Issue of Loongson-2F,We need to do:

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

This patch did clear BTB(branch target buffer), forbid RAS(row address strobe)
via Loongson-2F's 64bit diagnostic register.

[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>
---
 arch/mips/include/asm/stackframe.h |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/arch/mips/include/asm/stackframe.h 
b/arch/mips/include/asm/stackframe.h
index 3b6da33..52a62f5 100644
--- a/arch/mips/include/asm/stackframe.h
+++ b/arch/mips/include/asm/stackframe.h
@@ -121,6 +121,25 @@
                .endm
 #else
                .macro  get_saved_sp    /* Uniprocessor variation */
+#ifdef CONFIG_CPU_LOONGSON2F
+               /*
+                * Clear BTB (branch target buffer), forbid RAS (row address
+                * strobe) 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
-- 
1.7.0.1


<Prev in Thread] Current Thread [Next in Thread>