xref: /openbmc/u-boot/arch/powerpc/lib/time.c (revision e89516f0)
1 /*
2  * (C) Copyright 2000, 2001
3  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4  *
5  * See file CREDITS for list of people who contributed to this
6  * project.
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 as
10  * published by the Free Software Foundation; either version 2 of
11  * the License, or (at your option) any later version.
12  *
13  * This program is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16  * GNU General Public License for more details.
17  *
18  * You should have received a copy of the GNU General Public License
19  * along with this program; if not, write to the Free Software
20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
21  * MA 02111-1307 USA
22  */
23 
24 #include <common.h>
25 
26 /* ------------------------------------------------------------------------- */
27 
28 /*
29  * This function is intended for SHORT delays only.
30  * It will overflow at around 10 seconds @ 400MHz,
31  * or 20 seconds @ 200MHz.
32  */
33 unsigned long usec2ticks(unsigned long usec)
34 {
35 	ulong ticks;
36 
37 	if (usec < 1000) {
38 		ticks = ((usec * (get_tbclk()/1000)) + 500) / 1000;
39 	} else {
40 		ticks = ((usec / 10) * (get_tbclk() / 100000));
41 	}
42 
43 	return (ticks);
44 }
45 
46 /* ------------------------------------------------------------------------- */
47 
48 /*
49  * We implement the delay by converting the delay (the number of
50  * microseconds to wait) into a number of time base ticks; then we
51  * watch the time base until it has incremented by that amount.
52  */
53 void __udelay(unsigned long usec)
54 {
55 	ulong ticks = usec2ticks (usec);
56 	wait_ticks (ticks);
57 }
58 
59 /* ------------------------------------------------------------------------- */
60 #ifndef CONFIG_NAND_SPL
61 unsigned long ticks2usec(unsigned long ticks)
62 {
63 	ulong tbclk = get_tbclk();
64 
65 	/* usec = ticks * 1000000 / tbclk
66 	 * Multiplication would overflow at ~4.2e3 ticks,
67 	 * so we break it up into
68 	 * usec = ( ( ticks * 1000) / tbclk ) * 1000;
69 	 */
70 	ticks *= 1000L;
71 	ticks /= tbclk;
72 	ticks *= 1000L;
73 
74 	return ((ulong)ticks);
75 }
76 #endif
77 /* ------------------------------------------------------------------------- */
78 
79 int init_timebase (void)
80 {
81 	unsigned long temp;
82 
83 #if defined(CONFIG_5xx) || defined(CONFIG_8xx)
84 	volatile immap_t *immap = (immap_t *) CONFIG_SYS_IMMR;
85 
86 	/* unlock */
87 	immap->im_sitk.sitk_tbk = KAPWR_KEY;
88 #endif
89 
90 	/* reset */
91 	asm volatile("li %0,0 ; mttbu %0 ; mttbl %0;"
92 	     : "=&r"(temp) );
93 
94 #if defined(CONFIG_5xx) || defined(CONFIG_8xx)
95 	/* enable */
96 	immap->im_sit.sit_tbscr |= TBSCR_TBE;
97 #endif
98 	return (0);
99 }
100 /* ------------------------------------------------------------------------- */
101