summaryrefslogtreecommitdiff
path: root/arch/powerpc/kernel/vdso32/gettimeofday.S
blob: a3951567118a9bbabd256ea418e57b346cc5c1a7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Userland implementation of gettimeofday() for 32 bits processes in a
 * ppc64 kernel for use in the vDSO
 *
 * Copyright (C) 2004 Benjamin Herrenschmuidt (benh@kernel.crashing.org,
 *                    IBM Corp.
 */
#include <asm/processor.h>
#include <asm/ppc_asm.h>
#include <asm/vdso.h>
#include <asm/vdso_datapage.h>
#include <asm/asm-offsets.h>
#include <asm/unistd.h>

/* Offset for the low 32-bit part of a field of long type */
#ifdef CONFIG_PPC64
#define LOPART	4
#else
#define LOPART	0
#endif

	.text
/*
 * Exact prototype of gettimeofday
 *
 * int __kernel_gettimeofday(struct timeval *tv, struct timezone *tz);
 *
 */
V_FUNCTION_BEGIN(__kernel_gettimeofday)
  .cfi_startproc
	mflr	r12
  .cfi_register lr,r12

	mr.	r10,r3			/* r10 saves tv */
	mr	r11,r4			/* r11 saves tz */
	get_datapage	r9, r0
	beq	3f
	LOAD_REG_IMMEDIATE(r7, 1000000)	/* load up USEC_PER_SEC */
	bl	__do_get_tspec@local	/* get sec/usec from tb & kernel */
	stw	r3,TVAL32_TV_SEC(r10)
	stw	r4,TVAL32_TV_USEC(r10)

3:	cmplwi	r11,0			/* check if tz is NULL */
	mtlr	r12
	crclr	cr0*4+so
	li	r3,0
	beqlr

	lwz	r4,CFG_TZ_MINUTEWEST(r9)/* fill tz */
	lwz	r5,CFG_TZ_DSTTIME(r9)
	stw	r4,TZONE_TZ_MINWEST(r11)
	stw	r5,TZONE_TZ_DSTTIME(r11)

	blr
  .cfi_endproc
V_FUNCTION_END(__kernel_gettimeofday)

/*
 * Exact prototype of clock_gettime()
 *
 * int __kernel_clock_gettime(clockid_t clock_id, struct timespec *tp);
 *
 */
V_FUNCTION_BEGIN(__kernel_clock_gettime)
  .cfi_startproc
	/* Check for supported clock IDs */
	cmpli	cr0,r3,CLOCK_REALTIME
	cmpli	cr1,r3,CLOCK_MONOTONIC
	cror	cr0*4+eq,cr0*4+eq,cr1*4+eq

	cmpli	cr5,r3,CLOCK_REALTIME_COARSE
	cmpli	cr6,r3,CLOCK_MONOTONIC_COARSE
	cror	cr5*4+eq,cr5*4+eq,cr6*4+eq

	cror	cr0*4+eq,cr0*4+eq,cr5*4+eq
	bne	cr0, .Lgettime_fallback

	mflr	r12			/* r12 saves lr */
  .cfi_register lr,r12
	mr	r11,r4			/* r11 saves tp */
	get_datapage	r9, r0
	LOAD_REG_IMMEDIATE(r7, NSEC_PER_SEC)	/* load up NSEC_PER_SEC */
	beq	cr5, .Lcoarse_clocks
.Lprecise_clocks:
	bl	__do_get_tspec@local	/* get sec/nsec from tb & kernel */
	bne	cr1, .Lfinish		/* not monotonic -> all done */

	/*
	 * CLOCK_MONOTONIC
	 */

	/* now we must fixup using wall to monotonic. We need to snapshot
	 * that value and do the counter trick again. Fortunately, we still
	 * have the counter value in r8 that was returned by __do_get_xsec.
	 * At this point, r3,r4 contain our sec/nsec values, r5 and r6
	 * can be used, r7 contains NSEC_PER_SEC.
	 */

	lwz	r5,(WTOM_CLOCK_SEC+LOPART)(r9)
	lwz	r6,WTOM_CLOCK_NSEC(r9)

	/* We now have our offset in r5,r6. We create a fake dependency
	 * on that value and re-check the counter
	 */
	or	r0,r6,r5
	xor	r0,r0,r0
	add	r9,r9,r0
	lwz	r0,(CFG_TB_UPDATE_COUNT+LOPART)(r9)
        cmpl    cr0,r8,r0		/* check if updated */
	bne-	.Lprecise_clocks
	b	.Lfinish_monotonic

	/*
	 * For coarse clocks we get data directly from the vdso data page, so
	 * we don't need to call __do_get_tspec, but we still need to do the
	 * counter trick.
	 */
.Lcoarse_clocks:
	lwz	r8,(CFG_TB_UPDATE_COUNT+LOPART)(r9)
	andi.	r0,r8,1                 /* pending update ? loop */
	bne-	.Lcoarse_clocks
	add	r9,r9,r0		/* r0 is already 0 */

	/*
	 * CLOCK_REALTIME_COARSE, below values are needed for MONOTONIC_COARSE
	 * too
	 */
	lwz	r3,STAMP_XTIME_SEC+LOPART(r9)
	lwz	r4,STAMP_XTIME_NSEC+LOPART(r9)
	bne	cr6,1f

	/* CLOCK_MONOTONIC_COARSE */
	lwz	r5,(WTOM_CLOCK_SEC+LOPART)(r9)
	lwz	r6,WTOM_CLOCK_NSEC(r9)

	/* check if counter has updated */
	or	r0,r6,r5
1:	or	r0,r0,r3
	or	r0,r0,r4
	xor	r0,r0,r0
	add	r3,r3,r0
	lwz	r0,CFG_TB_UPDATE_COUNT+LOPART(r9)
	cmpl	cr0,r0,r8               /* check if updated */
	bne-	.Lcoarse_clocks

	/* Counter has not updated, so continue calculating proper values for
	 * sec and nsec if monotonic coarse, or just return with the proper
	 * values for realtime.
	 */
	bne	cr6, .Lfinish

	/* Calculate and store result. Note that this mimics the C code,
	 * which may cause funny results if nsec goes negative... is that
	 * possible at all ?
	 */
.Lfinish_monotonic:
	add	r3,r3,r5
	add	r4,r4,r6
	cmpw	cr0,r4,r7
	cmpwi	cr1,r4,0
	blt	1f
	subf	r4,r7,r4
	addi	r3,r3,1
1:	bge	cr1, .Lfinish
	addi	r3,r3,-1
	add	r4,r4,r7

.Lfinish:
	stw	r3,TSPC32_TV_SEC(r11)
	stw	r4,TSPC32_TV_NSEC(r11)

	mtlr	r12
	crclr	cr0*4+so
	li	r3,0
	blr

	/*
	 * syscall fallback
	 */
.Lgettime_fallback:
	li	r0,__NR_clock_gettime
  .cfi_restore lr
	sc
	blr
  .cfi_endproc
V_FUNCTION_END(__kernel_clock_gettime)


/*
 * Exact prototype of clock_getres()
 *
 * int __kernel_clock_getres(clockid_t clock_id, struct timespec *res);
 *
 */
V_FUNCTION_BEGIN(__kernel_clock_getres)
  .cfi_startproc
	/* Check for supported clock IDs */
	cmplwi	cr0, r3, CLOCK_MAX
	cmpwi	cr1, r3, CLOCK_REALTIME_COARSE
	cmpwi	cr7, r3, CLOCK_MONOTONIC_COARSE
	bgt	cr0, 99f
	LOAD_REG_IMMEDIATE(r5, KTIME_LOW_RES)
	beq	cr1, 1f
	beq	cr7, 1f

	mflr	r12
  .cfi_register lr,r12
	get_datapage	r3, r0
	lwz	r5, CLOCK_HRTIMER_RES(r3)
	mtlr	r12
1:	li	r3,0
	cmpli	cr0,r4,0
	crclr	cr0*4+so
	beqlr
	stw	r3,TSPC32_TV_SEC(r4)
	stw	r5,TSPC32_TV_NSEC(r4)
	blr

	/*
	 * invalid clock
	 */
99:
	li	r3, EINVAL
	crset	so
	blr
  .cfi_endproc
V_FUNCTION_END(__kernel_clock_getres)


/*
 * Exact prototype of time()
 *
 * time_t time(time *t);
 *
 */
V_FUNCTION_BEGIN(__kernel_time)
  .cfi_startproc
	mflr	r12
  .cfi_register lr,r12

	mr	r11,r3			/* r11 holds t */
	get_datapage	r9, r0

	lwz	r3,STAMP_XTIME_SEC+LOPART(r9)

	cmplwi	r11,0			/* check if t is NULL */
	mtlr	r12
	crclr	cr0*4+so
	beqlr
	stw	r3,0(r11)		/* store result at *t */
	blr
  .cfi_endproc
V_FUNCTION_END(__kernel_time)

/*
 * This is the core of clock_gettime() and gettimeofday(),
 * it returns the current time in r3 (seconds) and r4.
 * On entry, r7 gives the resolution of r4, either USEC_PER_SEC
 * or NSEC_PER_SEC, giving r4 in microseconds or nanoseconds.
 * It expects the datapage ptr in r9 and doesn't clobber it.
 * It clobbers r0, r5 and r6.
 * On return, r8 contains the counter value that can be reused.
 * This clobbers cr0 but not any other cr field.
 */
__do_get_tspec:
  .cfi_startproc
	/* Check for update count & load values. We use the low
	 * order 32 bits of the update count
	 */
1:	lwz	r8,(CFG_TB_UPDATE_COUNT+LOPART)(r9)
	andi.	r0,r8,1			/* pending update ? loop */
	bne-	1b
	xor	r0,r8,r8		/* create dependency */
	add	r9,r9,r0

	/* Load orig stamp (offset to TB) */
	lwz	r5,CFG_TB_ORIG_STAMP(r9)
	lwz	r6,(CFG_TB_ORIG_STAMP+4)(r9)

	/* Get a stable TB value */
2:	MFTBU(r3)
	MFTBL(r4)
	MFTBU(r0)
	cmplw	cr0,r3,r0
	bne-	2b

	/* Subtract tb orig stamp and shift left 12 bits.
	 */
	subfc	r4,r6,r4
	subfe	r0,r5,r3
	slwi	r0,r0,12
	rlwimi.	r0,r4,12,20,31
	slwi	r4,r4,12

	/*
	 * Load scale factor & do multiplication.
	 * We only use the high 32 bits of the tb_to_xs value.
	 * Even with a 1GHz timebase clock, the high 32 bits of
	 * tb_to_xs will be at least 4 million, so the error from
	 * ignoring the low 32 bits will be no more than 0.25ppm.
	 * The error will just make the clock run very very slightly
	 * slow until the next time the kernel updates the VDSO data,
	 * at which point the clock will catch up to the kernel's value,
	 * so there is no long-term error accumulation.
	 */
	lwz	r5,CFG_TB_TO_XS(r9)	/* load values */
	mulhwu	r4,r4,r5
	li	r3,0

	beq+	4f			/* skip high part computation if 0 */
	mulhwu	r3,r0,r5
	mullw	r5,r0,r5
	addc	r4,r4,r5
	addze	r3,r3
4:
	/* At this point, we have seconds since the xtime stamp
	 * as a 32.32 fixed-point number in r3 and r4.
	 * Load & add the xtime stamp.
	 */
	lwz	r5,STAMP_XTIME_SEC+LOPART(r9)
	lwz	r6,STAMP_SEC_FRAC(r9)
	addc	r4,r4,r6
	adde	r3,r3,r5

	/* We create a fake dependency on the result in r3/r4
	 * and re-check the counter
	 */
	or	r6,r4,r3
	xor	r0,r6,r6
	add	r9,r9,r0
	lwz	r0,(CFG_TB_UPDATE_COUNT+LOPART)(r9)
        cmplw	cr0,r8,r0		/* check if updated */
	bne-	1b

	mulhwu	r4,r4,r7		/* convert to micro or nanoseconds */

	blr
  .cfi_endproc