/arch/ppc64/kernel/vdso64/gettimeofday.S

 1/*
 2 * Userland implementation of gettimeofday() for 64 bits processes in a
 3 * ppc64 kernel for use in the vDSO
 4 *
 5 * Copyright (C) 2004 Benjamin Herrenschmuidt (benh@kernel.crashing.org),
 6 *                    IBM Corp.
 7 *
 8 * This program is free software; you can redistribute it and/or
 9 * modify it under the terms of the GNU General Public License
10 * as published by the Free Software Foundation; either version
11 * 2 of the License, or (at your option) any later version.
12 */
13#include <linux/config.h>
14#include <asm/processor.h>
15#include <asm/ppc_asm.h>
16#include <asm/vdso.h>
17#include <asm/offsets.h>
18
19	.text
20/*
21 * Exact prototype of gettimeofday
22 *
23 * int __kernel_gettimeofday(struct timeval *tv, struct timezone *tz);
24 *
25 */
26V_FUNCTION_BEGIN(__kernel_gettimeofday)
27  .cfi_startproc
28	mflr	r12
29  .cfi_register lr,r12
30
31	mr	r11,r3			/* r11 holds tv */
32	mr	r10,r4			/* r10 holds tz */
33	bl	V_LOCAL_FUNC(__get_datapage)		/* get data page */
34	bl	V_LOCAL_FUNC(__do_get_xsec)		/* get xsec from tb & kernel */
35	lis     r7,15			/* r7 = 1000000 = USEC_PER_SEC */
36	ori     r7,r7,16960
37	rldicl  r5,r4,44,20		/* r5 = sec = xsec / XSEC_PER_SEC */
38	rldicr  r6,r5,20,43		/* r6 = sec * XSEC_PER_SEC */
39	std	r5,TVAL64_TV_SEC(r11)	/* store sec in tv */
40	subf	r0,r6,r4		/* r0 = xsec = (xsec - r6) */
41	mulld   r0,r0,r7		/* usec = (xsec * USEC_PER_SEC) / XSEC_PER_SEC */
42	rldicl  r0,r0,44,20
43	cmpldi	cr0,r10,0		/* check if tz is NULL */
44	std	r0,TVAL64_TV_USEC(r11)	/* store usec in tv */
45	beq	1f
46	lwz	r4,CFG_TZ_MINUTEWEST(r3)/* fill tz */
47	lwz	r5,CFG_TZ_DSTTIME(r3)
48	stw	r4,TZONE_TZ_MINWEST(r10)
49	stw	r5,TZONE_TZ_DSTTIME(r10)
501:	mtlr	r12
51	li	r3,0			/* always success */
52	blr
53  .cfi_endproc
54V_FUNCTION_END(__kernel_gettimeofday)
55
56
57/*
58 * This is the core of gettimeofday(), it returns the xsec
59 * value in r4 and expects the datapage ptr (non clobbered)
60 * in r3. clobbers r0,r4,r5,r6,r7,r8
61*/
62V_FUNCTION_BEGIN(__do_get_xsec)
63  .cfi_startproc
64	/* check for update count & load values */
651:	ld	r7,CFG_TB_UPDATE_COUNT(r3)
66	andi.	r0,r4,1			/* pending update ? loop */
67	bne-	1b
68	xor	r0,r4,r4		/* create dependency */
69	add	r3,r3,r0
70
71	/* Get TB & offset it */
72	mftb	r8
73	ld	r9,CFG_TB_ORIG_STAMP(r3)
74	subf	r8,r9,r8
75
76	/* Scale result */
77	ld	r5,CFG_TB_TO_XS(r3)
78	mulhdu	r8,r8,r5
79
80	/* Add stamp since epoch */
81	ld	r6,CFG_STAMP_XSEC(r3)
82	add	r4,r6,r8
83
84	xor	r0,r4,r4
85	add	r3,r3,r0
86	ld	r0,CFG_TB_UPDATE_COUNT(r3)
87        cmpld   cr0,r0,r7		/* check if updated */
88	bne-	1b
89	blr
90  .cfi_endproc
91V_FUNCTION_END(__do_get_xsec)