xref: /openbmc/linux/arch/arm/lib/csumpartial.S (revision 1da177e4) 
1/*
2 *  linux/arch/arm/lib/csumpartial.S
3 *
4 *  Copyright (C) 1995-1998 Russell King
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
10#include <linux/linkage.h>
11#include <asm/assembler.h>
12
13		.text
14
15/*
16 * Function: __u32 csum_partial(const char *src, int len, __u32 sum)
17 * Params  : r0 = buffer, r1 = len, r2 = checksum
18 * Returns : r0 = new checksum
19 */
20
21buf	.req	r0
22len	.req	r1
23sum	.req	r2
24td0	.req	r3
25td1	.req	r4	@ save before use
26td2	.req	r5	@ save before use
27td3	.req	lr
28
29.zero:		mov	r0, sum
30		add	sp, sp, #4
31		ldr	pc, [sp], #4
32
33		/*
34		 * Handle 0 to 7 bytes, with any alignment of source and
35		 * destination pointers.  Note that when we get here, C = 0
36		 */
37.less8:		teq	len, #0			@ check for zero count
38		beq	.zero
39
40		/* we must have at least one byte. */
41		tst	buf, #1			@ odd address?
42		ldrneb	td0, [buf], #1
43		subne	len, len, #1
44		adcnes	sum, sum, td0, put_byte_1
45
46.less4:		tst	len, #6
47		beq	.less8_byte
48
49		/* we are now half-word aligned */
50
51.less8_wordlp:
52#if __LINUX_ARM_ARCH__ >= 4
53		ldrh	td0, [buf], #2
54		sub	len, len, #2
55#else
56		ldrb	td0, [buf], #1
57		ldrb	td3, [buf], #1
58		sub	len, len, #2
59#ifndef __ARMEB__
60		orr	td0, td0, td3, lsl #8
61#else
62		orr	td0, td3, td0, lsl #8
63#endif
64#endif
65		adcs	sum, sum, td0
66		tst	len, #6
67		bne	.less8_wordlp
68
69.less8_byte:	tst	len, #1			@ odd number of bytes
70		ldrneb	td0, [buf], #1		@ include last byte
71		adcnes	sum, sum, td0, put_byte_0	@ update checksum
72
73.done:		adc	r0, sum, #0		@ collect up the last carry
74		ldr	td0, [sp], #4
75		tst	td0, #1			@ check buffer alignment
76		movne	r0, r0, ror #8		@ rotate checksum by 8 bits
77		ldr	pc, [sp], #4		@ return
78
79.not_aligned:	tst	buf, #1			@ odd address
80		ldrneb	td0, [buf], #1		@ make even
81		subne	len, len, #1
82		adcnes	sum, sum, td0, put_byte_1	@ update checksum
83
84		tst	buf, #2			@ 32-bit aligned?
85#if __LINUX_ARM_ARCH__ >= 4
86		ldrneh	td0, [buf], #2		@ make 32-bit aligned
87		subne	len, len, #2
88#else
89		ldrneb	td0, [buf], #1
90		ldrneb	ip, [buf], #1
91		subne	len, len, #2
92#ifndef __ARMEB__
93		orrne	td0, td0, ip, lsl #8
94#else
95		orrne	td0, ip, td0, lsl #8
96#endif
97#endif
98		adcnes	sum, sum, td0		@ update checksum
99		mov	pc, lr
100
101ENTRY(csum_partial)
102		stmfd	sp!, {buf, lr}
103		cmp	len, #8			@ Ensure that we have at least
104		blo	.less8			@ 8 bytes to copy.
105
106		adds	sum, sum, #0		@ C = 0
107		tst	buf, #3			@ Test destination alignment
108		blne	.not_aligned		@ aligh destination, return here
109
1101:		bics	ip, len, #31
111		beq	3f
112
113		stmfd	sp!, {r4 - r5}
1142:		ldmia	buf!, {td0, td1, td2, td3}
115		adcs	sum, sum, td0
116		adcs	sum, sum, td1
117		adcs	sum, sum, td2
118		adcs	sum, sum, td3
119		ldmia	buf!, {td0, td1, td2, td3}
120		adcs	sum, sum, td0
121		adcs	sum, sum, td1
122		adcs	sum, sum, td2
123		adcs	sum, sum, td3
124		sub	ip, ip, #32
125		teq	ip, #0
126		bne	2b
127		ldmfd	sp!, {r4 - r5}
128
1293:		tst	len, #0x1c		@ should not change C
130		beq	.less4
131
1324:		ldr	td0, [buf], #4
133		sub	len, len, #4
134		adcs	sum, sum, td0
135		tst	len, #0x1c
136		bne	4b
137		b	.less4
138