xref: /openbmc/linux/arch/xtensa/lib/checksum.S (revision 2208f39c) 
1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 * INET		An implementation of the TCP/IP protocol suite for the LINUX
4 *		operating system.  INET is implemented using the  BSD Socket
5 *		interface as the means of communication with the user level.
6 *
7 *		IP/TCP/UDP checksumming routines
8 *
9 * Xtensa version:  Copyright (C) 2001 Tensilica, Inc. by Kevin Chea
10 *                  Optimized by Joe Taylor
11 */
12
13#include <linux/errno.h>
14#include <linux/linkage.h>
15#include <asm/asmmacro.h>
16#include <asm/core.h>
17
18/*
19 * computes a partial checksum, e.g. for TCP/UDP fragments
20 */
21
22/*
23 * unsigned int csum_partial(const unsigned char *buf, int len,
24 *                           unsigned int sum);
25 *    a2 = buf
26 *    a3 = len
27 *    a4 = sum
28 *
29 * This function assumes 2- or 4-byte alignment.  Other alignments will fail!
30 */
31
32/* ONES_ADD converts twos-complement math to ones-complement. */
33#define ONES_ADD(sum, val)	  \
34	add	sum, sum, val	; \
35	bgeu	sum, val, 99f	; \
36	addi	sum, sum, 1	; \
3799:				;
38
39.text
40ENTRY(csum_partial)
41
42	/*
43	 * Experiments with Ethernet and SLIP connections show that buf
44	 * is aligned on either a 2-byte or 4-byte boundary.
45	 */
46	abi_entry_default
47	extui	a5, a2, 0, 2
48	bnez	a5, 8f		/* branch if 2-byte aligned */
49	/* Fall-through on common case, 4-byte alignment */
501:
51	srli	a5, a3, 5	/* 32-byte chunks */
52#if XCHAL_HAVE_LOOPS
53	loopgtz	a5, 2f
54#else
55	beqz	a5, 2f
56	slli	a5, a5, 5
57	add	a5, a5, a2	/* a5 = end of last 32-byte chunk */
58.Loop1:
59#endif
60	l32i	a6, a2, 0
61	l32i	a7, a2, 4
62	ONES_ADD(a4, a6)
63	ONES_ADD(a4, a7)
64	l32i	a6, a2, 8
65	l32i	a7, a2, 12
66	ONES_ADD(a4, a6)
67	ONES_ADD(a4, a7)
68	l32i	a6, a2, 16
69	l32i	a7, a2, 20
70	ONES_ADD(a4, a6)
71	ONES_ADD(a4, a7)
72	l32i	a6, a2, 24
73	l32i	a7, a2, 28
74	ONES_ADD(a4, a6)
75	ONES_ADD(a4, a7)
76	addi	a2, a2, 4*8
77#if !XCHAL_HAVE_LOOPS
78	blt	a2, a5, .Loop1
79#endif
802:
81	extui	a5, a3, 2, 3	/* remaining 4-byte chunks */
82#if XCHAL_HAVE_LOOPS
83	loopgtz	a5, 3f
84#else
85	beqz	a5, 3f
86	slli	a5, a5, 2
87	add	a5, a5, a2	/* a5 = end of last 4-byte chunk */
88.Loop2:
89#endif
90	l32i	a6, a2, 0
91	ONES_ADD(a4, a6)
92	addi	a2, a2, 4
93#if !XCHAL_HAVE_LOOPS
94	blt	a2, a5, .Loop2
95#endif
963:
97	_bbci.l	a3, 1, 5f	/* remaining 2-byte chunk */
98	l16ui	a6, a2, 0
99	ONES_ADD(a4, a6)
100	addi	a2, a2, 2
1015:
102	_bbci.l	a3, 0, 7f	/* remaining 1-byte chunk */
1036:	l8ui	a6, a2, 0
104#ifdef __XTENSA_EB__
105	slli	a6, a6, 8	/* load byte into bits 8..15 */
106#endif
107	ONES_ADD(a4, a6)
1087:
109	mov	a2, a4
110	abi_ret_default
111
112	/* uncommon case, buf is 2-byte aligned */
1138:
114	beqz	a3, 7b		/* branch if len == 0 */
115	beqi	a3, 1, 6b	/* branch if len == 1 */
116
117	extui	a5, a2, 0, 1
118	bnez	a5, 8f		/* branch if 1-byte aligned */
119
120	l16ui	a6, a2, 0	/* common case, len >= 2 */
121	ONES_ADD(a4, a6)
122	addi	a2, a2, 2	/* adjust buf */
123	addi	a3, a3, -2	/* adjust len */
124	j	1b		/* now buf is 4-byte aligned */
125
126	/* case: odd-byte aligned, len > 1
127	 * This case is dog slow, so don't give us an odd address.
128	 * (I don't think this ever happens, but just in case.)
129	 */
1308:
131	srli	a5, a3, 2	/* 4-byte chunks */
132#if XCHAL_HAVE_LOOPS
133	loopgtz	a5, 2f
134#else
135	beqz	a5, 2f
136	slli	a5, a5, 2
137	add	a5, a5, a2	/* a5 = end of last 4-byte chunk */
138.Loop3:
139#endif
140	l8ui	a6, a2, 0	/* bits 24..31 */
141	l16ui	a7, a2, 1	/* bits  8..23 */
142	l8ui	a8, a2, 3	/* bits  0.. 8 */
143#ifdef	__XTENSA_EB__
144	slli	a6, a6, 24
145#else
146	slli	a8, a8, 24
147#endif
148	slli	a7, a7, 8
149	or	a7, a7, a6
150	or	a7, a7, a8
151	ONES_ADD(a4, a7)
152	addi	a2, a2, 4
153#if !XCHAL_HAVE_LOOPS
154	blt	a2, a5, .Loop3
155#endif
1562:
157	_bbci.l	a3, 1, 3f	/* remaining 2-byte chunk, still odd addr */
158	l8ui	a6, a2, 0
159	l8ui	a7, a2, 1
160#ifdef	__XTENSA_EB__
161	slli	a6, a6, 8
162#else
163	slli	a7, a7, 8
164#endif
165	or	a7, a7, a6
166	ONES_ADD(a4, a7)
167	addi	a2, a2, 2
1683:
169	j	5b		/* branch to handle the remaining byte */
170
171ENDPROC(csum_partial)
172
173/*
174 * Copy from ds while checksumming, otherwise like csum_partial
175 */
176
177/*
178unsigned int csum_partial_copy_generic (const char *src, char *dst, int len)
179	a2  = src
180	a3  = dst
181	a4  = len
182	a5  = sum
183	a8  = temp
184	a9  = temp
185	a10 = temp
186
187    This function is optimized for 4-byte aligned addresses.  Other
188    alignments work, but not nearly as efficiently.
189 */
190
191ENTRY(csum_partial_copy_generic)
192
193	abi_entry_default
194	movi	a5, -1
195	or	a10, a2, a3
196
197	/* We optimize the following alignment tests for the 4-byte
198	aligned case.  Two bbsi.l instructions might seem more optimal
199	(commented out below).  However, both labels 5: and 3: are out
200	of the imm8 range, so the assembler relaxes them into
201	equivalent bbci.l, j combinations, which is actually
202	slower. */
203
204	extui	a9, a10, 0, 2
205	beqz	a9, 1f		/* branch if both are 4-byte aligned */
206	bbsi.l	a10, 0, 5f	/* branch if one address is odd */
207	j	3f		/* one address is 2-byte aligned */
208
209/*	_bbsi.l	a10, 0, 5f */	/* branch if odd address */
210/*	_bbsi.l	a10, 1, 3f */	/* branch if 2-byte-aligned address */
211
2121:
213	/* src and dst are both 4-byte aligned */
214	srli	a10, a4, 5	/* 32-byte chunks */
215#if XCHAL_HAVE_LOOPS
216	loopgtz	a10, 2f
217#else
218	beqz	a10, 2f
219	slli	a10, a10, 5
220	add	a10, a10, a2	/* a10 = end of last 32-byte src chunk */
221.Loop5:
222#endif
223EX(10f)	l32i	a9, a2, 0
224EX(10f)	l32i	a8, a2, 4
225EX(10f)	s32i	a9, a3, 0
226EX(10f)	s32i	a8, a3, 4
227	ONES_ADD(a5, a9)
228	ONES_ADD(a5, a8)
229EX(10f)	l32i	a9, a2, 8
230EX(10f)	l32i	a8, a2, 12
231EX(10f)	s32i	a9, a3, 8
232EX(10f)	s32i	a8, a3, 12
233	ONES_ADD(a5, a9)
234	ONES_ADD(a5, a8)
235EX(10f)	l32i	a9, a2, 16
236EX(10f)	l32i	a8, a2, 20
237EX(10f)	s32i	a9, a3, 16
238EX(10f)	s32i	a8, a3, 20
239	ONES_ADD(a5, a9)
240	ONES_ADD(a5, a8)
241EX(10f)	l32i	a9, a2, 24
242EX(10f)	l32i	a8, a2, 28
243EX(10f)	s32i	a9, a3, 24
244EX(10f)	s32i	a8, a3, 28
245	ONES_ADD(a5, a9)
246	ONES_ADD(a5, a8)
247	addi	a2, a2, 32
248	addi	a3, a3, 32
249#if !XCHAL_HAVE_LOOPS
250	blt	a2, a10, .Loop5
251#endif
2522:
253	extui	a10, a4, 2, 3	/* remaining 4-byte chunks */
254	extui	a4, a4, 0, 2	/* reset len for general-case, 2-byte chunks */
255#if XCHAL_HAVE_LOOPS
256	loopgtz	a10, 3f
257#else
258	beqz	a10, 3f
259	slli	a10, a10, 2
260	add	a10, a10, a2	/* a10 = end of last 4-byte src chunk */
261.Loop6:
262#endif
263EX(10f)	l32i	a9, a2, 0
264EX(10f)	s32i	a9, a3, 0
265	ONES_ADD(a5, a9)
266	addi	a2, a2, 4
267	addi	a3, a3, 4
268#if !XCHAL_HAVE_LOOPS
269	blt	a2, a10, .Loop6
270#endif
2713:
272	/*
273	Control comes to here in two cases: (1) It may fall through
274	to here from the 4-byte alignment case to process, at most,
275	one 2-byte chunk.  (2) It branches to here from above if
276	either src or dst is 2-byte aligned, and we process all bytes
277	here, except for perhaps a trailing odd byte.  It's
278	inefficient, so align your addresses to 4-byte boundaries.
279
280	a2 = src
281	a3 = dst
282	a4 = len
283	a5 = sum
284	*/
285	srli	a10, a4, 1	/* 2-byte chunks */
286#if XCHAL_HAVE_LOOPS
287	loopgtz	a10, 4f
288#else
289	beqz	a10, 4f
290	slli	a10, a10, 1
291	add	a10, a10, a2	/* a10 = end of last 2-byte src chunk */
292.Loop7:
293#endif
294EX(10f)	l16ui	a9, a2, 0
295EX(10f)	s16i	a9, a3, 0
296	ONES_ADD(a5, a9)
297	addi	a2, a2, 2
298	addi	a3, a3, 2
299#if !XCHAL_HAVE_LOOPS
300	blt	a2, a10, .Loop7
301#endif
3024:
303	/* This section processes a possible trailing odd byte. */
304	_bbci.l	a4, 0, 8f	/* 1-byte chunk */
305EX(10f)	l8ui	a9, a2, 0
306EX(10f)	s8i	a9, a3, 0
307#ifdef __XTENSA_EB__
308	slli	a9, a9, 8	/* shift byte to bits 8..15 */
309#endif
310	ONES_ADD(a5, a9)
3118:
312	mov	a2, a5
313	abi_ret_default
314
3155:
316	/* Control branch to here when either src or dst is odd.  We
317	process all bytes using 8-bit accesses.  Grossly inefficient,
318	so don't feed us an odd address. */
319
320	srli	a10, a4, 1	/* handle in pairs for 16-bit csum */
321#if XCHAL_HAVE_LOOPS
322	loopgtz	a10, 6f
323#else
324	beqz	a10, 6f
325	slli	a10, a10, 1
326	add	a10, a10, a2	/* a10 = end of last odd-aligned, 2-byte src chunk */
327.Loop8:
328#endif
329EX(10f)	l8ui	a9, a2, 0
330EX(10f)	l8ui	a8, a2, 1
331EX(10f)	s8i	a9, a3, 0
332EX(10f)	s8i	a8, a3, 1
333#ifdef __XTENSA_EB__
334	slli	a9, a9, 8	/* combine into a single 16-bit value */
335#else				/* for checksum computation */
336	slli	a8, a8, 8
337#endif
338	or	a9, a9, a8
339	ONES_ADD(a5, a9)
340	addi	a2, a2, 2
341	addi	a3, a3, 2
342#if !XCHAL_HAVE_LOOPS
343	blt	a2, a10, .Loop8
344#endif
3456:
346	j	4b		/* process the possible trailing odd byte */
347
348ENDPROC(csum_partial_copy_generic)
349
350
351# Exception handler:
352.section .fixup, "ax"
35310:
354	movi	a2, 0
355	abi_ret_default
356
357.previous
358