1 /*
2  * This file is subject to the terms and conditions of the GNU General Public
3  * License.  See the file "COPYING" in the main directory of this archive
4  * for more details.
5  *
6  * Copyright (C) 2007 by Ralf Baechle
7  */
8 #include <linux/clocksource.h>
9 #include <linux/init.h>
10 
11 #include <asm/time.h>
12 
13 #include <asm/octeon/octeon.h>
14 #include <asm/octeon/cvmx-ipd-defs.h>
15 
16 /*
17  * Set the current core's cvmcount counter to the value of the
18  * IPD_CLK_COUNT.  We do this on all cores as they are brought
19  * on-line.  This allows for a read from a local cpu register to
20  * access a synchronized counter.
21  *
22  */
23 void octeon_init_cvmcount(void)
24 {
25 	unsigned long flags;
26 	unsigned loops = 2;
27 
28 	/* Clobber loops so GCC will not unroll the following while loop. */
29 	asm("" : "+r" (loops));
30 
31 	local_irq_save(flags);
32 	/*
33 	 * Loop several times so we are executing from the cache,
34 	 * which should give more deterministic timing.
35 	 */
36 	while (loops--)
37 		write_c0_cvmcount(cvmx_read_csr(CVMX_IPD_CLK_COUNT));
38 	local_irq_restore(flags);
39 }
40 
41 static cycle_t octeon_cvmcount_read(struct clocksource *cs)
42 {
43 	return read_c0_cvmcount();
44 }
45 
46 static struct clocksource clocksource_mips = {
47 	.name		= "OCTEON_CVMCOUNT",
48 	.read		= octeon_cvmcount_read,
49 	.mask		= CLOCKSOURCE_MASK(64),
50 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
51 };
52 
53 unsigned long long notrace sched_clock(void)
54 {
55 	/* 64-bit arithmatic can overflow, so use 128-bit.  */
56 #if (__GNUC__ < 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ <= 3))
57 	u64 t1, t2, t3;
58 	unsigned long long rv;
59 	u64 mult = clocksource_mips.mult;
60 	u64 shift = clocksource_mips.shift;
61 	u64 cnt = read_c0_cvmcount();
62 
63 	asm (
64 		"dmultu\t%[cnt],%[mult]\n\t"
65 		"nor\t%[t1],$0,%[shift]\n\t"
66 		"mfhi\t%[t2]\n\t"
67 		"mflo\t%[t3]\n\t"
68 		"dsll\t%[t2],%[t2],1\n\t"
69 		"dsrlv\t%[rv],%[t3],%[shift]\n\t"
70 		"dsllv\t%[t1],%[t2],%[t1]\n\t"
71 		"or\t%[rv],%[t1],%[rv]\n\t"
72 		: [rv] "=&r" (rv), [t1] "=&r" (t1), [t2] "=&r" (t2), [t3] "=&r" (t3)
73 		: [cnt] "r" (cnt), [mult] "r" (mult), [shift] "r" (shift)
74 		: "hi", "lo");
75 	return rv;
76 #else
77 	/* GCC > 4.3 do it the easy way.  */
78 	unsigned int __attribute__((mode(TI))) t;
79 	t = read_c0_cvmcount();
80 	t = t * clocksource_mips.mult;
81 	return (unsigned long long)(t >> clocksource_mips.shift);
82 #endif
83 }
84 
85 void __init plat_time_init(void)
86 {
87 	clocksource_mips.rating = 300;
88 	clocksource_set_clock(&clocksource_mips, mips_hpt_frequency);
89 	clocksource_register(&clocksource_mips);
90 }
91