From: Vineet Gupta <vgupta@synopsys.com>
Date: Thu, 17 Apr 2014 11:43:26 +0000 (+0530)
Subject: ARC: optimize kernel bss clearing in early boot code
X-Git-Tag: firefly_0821_release~176^2~3688^2~3
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=bef444a33004f4062930df1fc703a25dd6d7b460;p=firefly-linux-kernel-4.4.55.git

ARC: optimize kernel bss clearing in early boot code

using ARC ZOL which reduces tot num of instructions by half

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---

diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S
index 07a58f2d3077..4d2481bd8b98 100644
--- a/arch/arc/kernel/head.S
+++ b/arch/arc/kernel/head.S
@@ -77,10 +77,11 @@ stext:
 	; Clear BSS before updating any globals
 	; XXX: use ZOL here
 	mov	r5, __bss_start
-	mov	r6, __bss_stop
+	sub	r6, __bss_stop, r5
+	lsr.f	lp_count, r6, 2
+	lpnz	1f
+	st.ab   0, [r5, 4]
 1:
-	st.ab   0, [r5,4]
-	brlt    r5, r6, 1b
 
 	; Uboot - kernel ABI
 	;    r0 = [0] No uboot interaction, [1] cmdline in r2, [2] DTB in r2
diff --git a/arch/arc/kernel/vmlinux.lds.S b/arch/arc/kernel/vmlinux.lds.S
index 2555f5886af6..dd35bde39f69 100644
--- a/arch/arc/kernel/vmlinux.lds.S
+++ b/arch/arc/kernel/vmlinux.lds.S
@@ -116,7 +116,7 @@ SECTIONS
 
 	_edata = .;
 
-	BSS_SECTION(0, 0, 0)
+	BSS_SECTION(4, 4, 4)
 
 #ifdef CONFIG_ARC_DW2_UNWIND
 	. = ALIGN(PAGE_SIZE);