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Diffstat (limited to 'arch/arm/mach-sa1100/cpu-sa1100.c')
-rw-r--r-- | arch/arm/mach-sa1100/cpu-sa1100.c | 249 |
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diff --git a/arch/arm/mach-sa1100/cpu-sa1100.c b/arch/arm/mach-sa1100/cpu-sa1100.c new file mode 100644 index 000000000000..6435b2e48ffa --- /dev/null +++ b/arch/arm/mach-sa1100/cpu-sa1100.c | |||
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1 | /* | ||
2 | * cpu-sa1100.c: clock scaling for the SA1100 | ||
3 | * | ||
4 | * Copyright (C) 2000 2001, The Delft University of Technology | ||
5 | * | ||
6 | * Authors: | ||
7 | * - Johan Pouwelse (J.A.Pouwelse@its.tudelft.nl): initial version | ||
8 | * - Erik Mouw (J.A.K.Mouw@its.tudelft.nl): | ||
9 | * - major rewrite for linux-2.3.99 | ||
10 | * - rewritten for the more generic power management scheme in | ||
11 | * linux-2.4.5-rmk1 | ||
12 | * | ||
13 | * This software has been developed while working on the LART | ||
14 | * computing board (http://www.lart.tudelft.nl/), which is | ||
15 | * sponsored by the Mobile Multi-media Communications | ||
16 | * (http://www.mmc.tudelft.nl/) and Ubiquitous Communications | ||
17 | * (http://www.ubicom.tudelft.nl/) projects. | ||
18 | * | ||
19 | * The authors can be reached at: | ||
20 | * | ||
21 | * Erik Mouw | ||
22 | * Information and Communication Theory Group | ||
23 | * Faculty of Information Technology and Systems | ||
24 | * Delft University of Technology | ||
25 | * P.O. Box 5031 | ||
26 | * 2600 GA Delft | ||
27 | * The Netherlands | ||
28 | * | ||
29 | * | ||
30 | * This program is free software; you can redistribute it and/or modify | ||
31 | * it under the terms of the GNU General Public License as published by | ||
32 | * the Free Software Foundation; either version 2 of the License, or | ||
33 | * (at your option) any later version. | ||
34 | * | ||
35 | * This program is distributed in the hope that it will be useful, | ||
36 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
37 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
38 | * GNU General Public License for more details. | ||
39 | * | ||
40 | * You should have received a copy of the GNU General Public License | ||
41 | * along with this program; if not, write to the Free Software | ||
42 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | ||
43 | * | ||
44 | * | ||
45 | * Theory of operations | ||
46 | * ==================== | ||
47 | * | ||
48 | * Clock scaling can be used to lower the power consumption of the CPU | ||
49 | * core. This will give you a somewhat longer running time. | ||
50 | * | ||
51 | * The SA-1100 has a single register to change the core clock speed: | ||
52 | * | ||
53 | * PPCR 0x90020014 PLL config | ||
54 | * | ||
55 | * However, the DRAM timings are closely related to the core clock | ||
56 | * speed, so we need to change these, too. The used registers are: | ||
57 | * | ||
58 | * MDCNFG 0xA0000000 DRAM config | ||
59 | * MDCAS0 0xA0000004 Access waveform | ||
60 | * MDCAS1 0xA0000008 Access waveform | ||
61 | * MDCAS2 0xA000000C Access waveform | ||
62 | * | ||
63 | * Care must be taken to change the DRAM parameters the correct way, | ||
64 | * because otherwise the DRAM becomes unusable and the kernel will | ||
65 | * crash. | ||
66 | * | ||
67 | * The simple solution to avoid a kernel crash is to put the actual | ||
68 | * clock change in ROM and jump to that code from the kernel. The main | ||
69 | * disadvantage is that the ROM has to be modified, which is not | ||
70 | * possible on all SA-1100 platforms. Another disadvantage is that | ||
71 | * jumping to ROM makes clock switching unecessary complicated. | ||
72 | * | ||
73 | * The idea behind this driver is that the memory configuration can be | ||
74 | * changed while running from DRAM (even with interrupts turned on!) | ||
75 | * as long as all re-configuration steps yield a valid DRAM | ||
76 | * configuration. The advantages are clear: it will run on all SA-1100 | ||
77 | * platforms, and the code is very simple. | ||
78 | * | ||
79 | * If you really want to understand what is going on in | ||
80 | * sa1100_update_dram_timings(), you'll have to read sections 8.2, | ||
81 | * 9.5.7.3, and 10.2 from the "Intel StrongARM SA-1100 Microprocessor | ||
82 | * Developers Manual" (available for free from Intel). | ||
83 | * | ||
84 | */ | ||
85 | |||
86 | #include <linux/kernel.h> | ||
87 | #include <linux/types.h> | ||
88 | #include <linux/init.h> | ||
89 | #include <linux/cpufreq.h> | ||
90 | |||
91 | #include <asm/hardware.h> | ||
92 | |||
93 | #include "generic.h" | ||
94 | |||
95 | typedef struct { | ||
96 | int speed; | ||
97 | u32 mdcnfg; | ||
98 | u32 mdcas0; | ||
99 | u32 mdcas1; | ||
100 | u32 mdcas2; | ||
101 | } sa1100_dram_regs_t; | ||
102 | |||
103 | |||
104 | static struct cpufreq_driver sa1100_driver; | ||
105 | |||
106 | static sa1100_dram_regs_t sa1100_dram_settings[] = | ||
107 | { | ||
108 | /* speed, mdcnfg, mdcas0, mdcas1, mdcas2 clock frequency */ | ||
109 | { 59000, 0x00dc88a3, 0xcccccccf, 0xfffffffc, 0xffffffff }, /* 59.0 MHz */ | ||
110 | { 73700, 0x011490a3, 0xcccccccf, 0xfffffffc, 0xffffffff }, /* 73.7 MHz */ | ||
111 | { 88500, 0x014e90a3, 0xcccccccf, 0xfffffffc, 0xffffffff }, /* 88.5 MHz */ | ||
112 | { 103200, 0x01889923, 0xcccccccf, 0xfffffffc, 0xffffffff }, /* 103.2 MHz */ | ||
113 | { 118000, 0x01c29923, 0x9999998f, 0xfffffff9, 0xffffffff }, /* 118.0 MHz */ | ||
114 | { 132700, 0x01fb2123, 0x9999998f, 0xfffffff9, 0xffffffff }, /* 132.7 MHz */ | ||
115 | { 147500, 0x02352123, 0x3333330f, 0xfffffff3, 0xffffffff }, /* 147.5 MHz */ | ||
116 | { 162200, 0x026b29a3, 0x38e38e1f, 0xfff8e38e, 0xffffffff }, /* 162.2 MHz */ | ||
117 | { 176900, 0x02a329a3, 0x71c71c1f, 0xfff1c71c, 0xffffffff }, /* 176.9 MHz */ | ||
118 | { 191700, 0x02dd31a3, 0xe38e383f, 0xffe38e38, 0xffffffff }, /* 191.7 MHz */ | ||
119 | { 206400, 0x03153223, 0xc71c703f, 0xffc71c71, 0xffffffff }, /* 206.4 MHz */ | ||
120 | { 221200, 0x034fba23, 0xc71c703f, 0xffc71c71, 0xffffffff }, /* 221.2 MHz */ | ||
121 | { 235900, 0x03853a23, 0xe1e1e07f, 0xe1e1e1e1, 0xffffffe1 }, /* 235.9 MHz */ | ||
122 | { 250700, 0x03bf3aa3, 0xc3c3c07f, 0xc3c3c3c3, 0xffffffc3 }, /* 250.7 MHz */ | ||
123 | { 265400, 0x03f7c2a3, 0xc3c3c07f, 0xc3c3c3c3, 0xffffffc3 }, /* 265.4 MHz */ | ||
124 | { 280200, 0x0431c2a3, 0x878780ff, 0x87878787, 0xffffff87 }, /* 280.2 MHz */ | ||
125 | { 0, 0, 0, 0, 0 } /* last entry */ | ||
126 | }; | ||
127 | |||
128 | static void sa1100_update_dram_timings(int current_speed, int new_speed) | ||
129 | { | ||
130 | sa1100_dram_regs_t *settings = sa1100_dram_settings; | ||
131 | |||
132 | /* find speed */ | ||
133 | while (settings->speed != 0) { | ||
134 | if(new_speed == settings->speed) | ||
135 | break; | ||
136 | |||
137 | settings++; | ||
138 | } | ||
139 | |||
140 | if (settings->speed == 0) { | ||
141 | panic("%s: couldn't find dram setting for speed %d\n", | ||
142 | __FUNCTION__, new_speed); | ||
143 | } | ||
144 | |||
145 | /* No risk, no fun: run with interrupts on! */ | ||
146 | if (new_speed > current_speed) { | ||
147 | /* We're going FASTER, so first relax the memory | ||
148 | * timings before changing the core frequency | ||
149 | */ | ||
150 | |||
151 | /* Half the memory access clock */ | ||
152 | MDCNFG |= MDCNFG_CDB2; | ||
153 | |||
154 | /* The order of these statements IS important, keep 8 | ||
155 | * pulses!! | ||
156 | */ | ||
157 | MDCAS2 = settings->mdcas2; | ||
158 | MDCAS1 = settings->mdcas1; | ||
159 | MDCAS0 = settings->mdcas0; | ||
160 | MDCNFG = settings->mdcnfg; | ||
161 | } else { | ||
162 | /* We're going SLOWER: first decrease the core | ||
163 | * frequency and then tighten the memory settings. | ||
164 | */ | ||
165 | |||
166 | /* Half the memory access clock */ | ||
167 | MDCNFG |= MDCNFG_CDB2; | ||
168 | |||
169 | /* The order of these statements IS important, keep 8 | ||
170 | * pulses!! | ||
171 | */ | ||
172 | MDCAS0 = settings->mdcas0; | ||
173 | MDCAS1 = settings->mdcas1; | ||
174 | MDCAS2 = settings->mdcas2; | ||
175 | MDCNFG = settings->mdcnfg; | ||
176 | } | ||
177 | } | ||
178 | |||
179 | static int sa1100_target(struct cpufreq_policy *policy, | ||
180 | unsigned int target_freq, | ||
181 | unsigned int relation) | ||
182 | { | ||
183 | unsigned int cur = sa11x0_getspeed(0); | ||
184 | unsigned int new_ppcr; | ||
185 | |||
186 | struct cpufreq_freqs freqs; | ||
187 | switch(relation){ | ||
188 | case CPUFREQ_RELATION_L: | ||
189 | new_ppcr = sa11x0_freq_to_ppcr(target_freq); | ||
190 | if (sa11x0_ppcr_to_freq(new_ppcr) > policy->max) | ||
191 | new_ppcr--; | ||
192 | break; | ||
193 | case CPUFREQ_RELATION_H: | ||
194 | new_ppcr = sa11x0_freq_to_ppcr(target_freq); | ||
195 | if ((sa11x0_ppcr_to_freq(new_ppcr) > target_freq) && | ||
196 | (sa11x0_ppcr_to_freq(new_ppcr - 1) >= policy->min)) | ||
197 | new_ppcr--; | ||
198 | break; | ||
199 | } | ||
200 | |||
201 | freqs.old = cur; | ||
202 | freqs.new = sa11x0_ppcr_to_freq(new_ppcr); | ||
203 | freqs.cpu = 0; | ||
204 | |||
205 | cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE); | ||
206 | |||
207 | if (freqs.new > cur) | ||
208 | sa1100_update_dram_timings(cur, freqs.new); | ||
209 | |||
210 | PPCR = new_ppcr; | ||
211 | |||
212 | if (freqs.new < cur) | ||
213 | sa1100_update_dram_timings(cur, freqs.new); | ||
214 | |||
215 | cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE); | ||
216 | |||
217 | return 0; | ||
218 | } | ||
219 | |||
220 | static int __init sa1100_cpu_init(struct cpufreq_policy *policy) | ||
221 | { | ||
222 | if (policy->cpu != 0) | ||
223 | return -EINVAL; | ||
224 | policy->cur = policy->min = policy->max = sa11x0_getspeed(0); | ||
225 | policy->governor = CPUFREQ_DEFAULT_GOVERNOR; | ||
226 | policy->cpuinfo.min_freq = 59000; | ||
227 | policy->cpuinfo.max_freq = 287000; | ||
228 | policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL; | ||
229 | return 0; | ||
230 | } | ||
231 | |||
232 | static struct cpufreq_driver sa1100_driver = { | ||
233 | .flags = CPUFREQ_STICKY, | ||
234 | .verify = sa11x0_verify_speed, | ||
235 | .target = sa1100_target, | ||
236 | .get = sa11x0_getspeed, | ||
237 | .init = sa1100_cpu_init, | ||
238 | .name = "sa1100", | ||
239 | }; | ||
240 | |||
241 | static int __init sa1100_dram_init(void) | ||
242 | { | ||
243 | if ((processor_id & CPU_SA1100_MASK) == CPU_SA1100_ID) | ||
244 | return cpufreq_register_driver(&sa1100_driver); | ||
245 | else | ||
246 | return -ENODEV; | ||
247 | } | ||
248 | |||
249 | arch_initcall(sa1100_dram_init); | ||