1 /*
2 * linux/arch/arm/mach-omap2/timer.c
3 *
4 * OMAP2 GP timer support.
5 *
6 * Copyright (C) 2009 Nokia Corporation
7 *
8 * Update to use new clocksource/clockevent layers
9 * Author: Kevin Hilman, MontaVista Software, Inc. <source@mvista.com>
10 * Copyright (C) 2007 MontaVista Software, Inc.
11 *
12 * Original driver:
13 * Copyright (C) 2005 Nokia Corporation
14 * Author: Paul Mundt <paul.mundt@nokia.com>
15 * Juha Yrjölä <juha.yrjola@nokia.com>
16 * OMAP Dual-mode timer framework support by Timo Teras
17 *
18 * Some parts based off of TI's 24xx code:
19 *
20 * Copyright (C) 2004-2009 Texas Instruments, Inc.
21 *
22 * Roughly modelled after the OMAP1 MPU timer code.
23 * Added OMAP4 support - Santosh Shilimkar <santosh.shilimkar@ti.com>
24 *
25 * This file is subject to the terms and conditions of the GNU General Public
26 * License. See the file "COPYING" in the main directory of this archive
27 * for more details.
28 */
29 #include <linux/clk.h>
30 #include <linux/clocksource.h>
31
32 #include "soc.h"
33 #include "common.h"
34 #include "control.h"
35 #include "omap-secure.h"
36
37 #define REALTIME_COUNTER_BASE 0x48243200
38 #define INCREMENTER_NUMERATOR_OFFSET 0x10
39 #define INCREMENTER_DENUMERATOR_RELOAD_OFFSET 0x14
40 #define NUMERATOR_DENUMERATOR_MASK 0xfffff000
41
42 static unsigned long arch_timer_freq;
43
44 void set_cntfreq(void)
45 {
46 omap_smc1(OMAP5_DRA7_MON_SET_CNTFRQ_INDEX, arch_timer_freq);
47 }
48
49 /*
50 * The realtime counter also called master counter, is a free-running
51 * counter, which is related to real time. It produces the count used
52 * by the CPU local timer peripherals in the MPU cluster. The timer counts
53 * at a rate of 6.144 MHz. Because the device operates on different clocks
54 * in different power modes, the master counter shifts operation between
55 * clocks, adjusting the increment per clock in hardware accordingly to
56 * maintain a constant count rate.
57 */
58 static void __init realtime_counter_init(void)
59 {
60 void __iomem *base;
61 static struct clk *sys_clk;
62 unsigned long rate;
63 unsigned int reg;
64 unsigned long long num, den;
65
66 base = ioremap(REALTIME_COUNTER_BASE, SZ_32);
67 if (!base) {
68 pr_err("%s: ioremap failed\n", __func__);
69 return;
70 }
71 sys_clk = clk_get(NULL, "sys_clkin");
72 if (IS_ERR(sys_clk)) {
73 pr_err("%s: failed to get system clock handle\n", __func__);
74 iounmap(base);
75 return;
76 }
77
78 rate = clk_get_rate(sys_clk);
79 clk_put(sys_clk);
80
81 if (soc_is_dra7xx()) {
82 /*
83 * Errata i856 says the 32.768KHz crystal does not start at
84 * power on, so the CPU falls back to an emulated 32KHz clock
85 * based on sysclk / 610 instead. This causes the master counter
86 * frequency to not be 6.144MHz but at sysclk / 610 * 375 / 2
87 * (OR sysclk * 75 / 244)
88 *
89 * This affects at least the DRA7/AM572x 1.0, 1.1 revisions.
90 * Of course any board built without a populated 32.768KHz
91 * crystal would also need this fix even if the CPU is fixed
92 * later.
93 *
94 * Either case can be detected by using the two speedselect bits
95 * If they are not 0, then the 32.768KHz clock driving the
96 * coarse counter that corrects the fine counter every time it
97 * ticks is actually rate/610 rather than 32.768KHz and we
98 * should compensate to avoid the 570ppm (at 20MHz, much worse
99 * at other rates) too fast system time.
100 */
101 reg = omap_ctrl_readl(DRA7_CTRL_CORE_BOOTSTRAP);
102 if (reg & DRA7_SPEEDSELECT_MASK) {
103 num = 75;
104 den = 244;
105 goto sysclk1_based;
106 }
107 }
108
109 /* Numerator/denumerator values refer TRM Realtime Counter section */
110 switch (rate) {
111 case 12000000:
112 num = 64;
113 den = 125;
114 break;
115 case 13000000:
116 num = 768;
117 den = 1625;
118 break;
119 case 19200000:
120 num = 8;
121 den = 25;
122 break;
123 case 20000000:
124 num = 192;
125 den = 625;
126 break;
127 case 26000000:
128 num = 384;
129 den = 1625;
130 break;
131 case 27000000:
132 num = 256;
133 den = 1125;
134 break;
135 case 38400000:
136 default:
137 /* Program it for 38.4 MHz */
138 num = 4;
139 den = 25;
140 break;
141 }
142
143 sysclk1_based:
144 /* Program numerator and denumerator registers */
145 reg = readl_relaxed(base + INCREMENTER_NUMERATOR_OFFSET) &
146 NUMERATOR_DENUMERATOR_MASK;
147 reg |= num;
148 writel_relaxed(reg, base + INCREMENTER_NUMERATOR_OFFSET);
149
150 reg = readl_relaxed(base + INCREMENTER_DENUMERATOR_RELOAD_OFFSET) &
151 NUMERATOR_DENUMERATOR_MASK;
152 reg |= den;
153 writel_relaxed(reg, base + INCREMENTER_DENUMERATOR_RELOAD_OFFSET);
154
155 arch_timer_freq = DIV_ROUND_UP_ULL(rate * num, den);
156 set_cntfreq();
157
158 iounmap(base);
159 }
160
161 void __init omap5_realtime_timer_init(void)
162 {
163 omap_clk_init();
164 realtime_counter_init();
165
166 timer_probe();
167 }
168
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.