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.lartmaker.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
95typedef struct {
96	int speed;
97	u32 mdcnfg;
98	u32 mdcas0;
99	u32 mdcas1;
100	u32 mdcas2;
101} sa1100_dram_regs_t;
102
103
104static struct cpufreq_driver sa1100_driver;
105
106static 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
128static 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
179static 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
220static 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
232static 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
241static 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
249arch_initcall(sa1100_dram_init);
250