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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/arm/mach-sa1100/cpu-sa1100.c
downloadlinux-stericsson-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+/*
+ * cpu-sa1100.c: clock scaling for the SA1100
+ *
+ * Copyright (C) 2000 2001, The Delft University of Technology
+ *
+ * Authors:
+ * - Johan Pouwelse (J.A.Pouwelse@its.tudelft.nl): initial version
+ * - Erik Mouw (J.A.K.Mouw@its.tudelft.nl):
+ * - major rewrite for linux-2.3.99
+ * - rewritten for the more generic power management scheme in
+ * linux-2.4.5-rmk1
+ *
+ * This software has been developed while working on the LART
+ * computing board (http://www.lart.tudelft.nl/), which is
+ * sponsored by the Mobile Multi-media Communications
+ * (http://www.mmc.tudelft.nl/) and Ubiquitous Communications
+ * (http://www.ubicom.tudelft.nl/) projects.
+ *
+ * The authors can be reached at:
+ *
+ * Erik Mouw
+ * Information and Communication Theory Group
+ * Faculty of Information Technology and Systems
+ * Delft University of Technology
+ * P.O. Box 5031
+ * 2600 GA Delft
+ * The Netherlands
+ *
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ *
+ * Theory of operations
+ * ====================
+ *
+ * Clock scaling can be used to lower the power consumption of the CPU
+ * core. This will give you a somewhat longer running time.
+ *
+ * The SA-1100 has a single register to change the core clock speed:
+ *
+ * PPCR 0x90020014 PLL config
+ *
+ * However, the DRAM timings are closely related to the core clock
+ * speed, so we need to change these, too. The used registers are:
+ *
+ * MDCNFG 0xA0000000 DRAM config
+ * MDCAS0 0xA0000004 Access waveform
+ * MDCAS1 0xA0000008 Access waveform
+ * MDCAS2 0xA000000C Access waveform
+ *
+ * Care must be taken to change the DRAM parameters the correct way,
+ * because otherwise the DRAM becomes unusable and the kernel will
+ * crash.
+ *
+ * The simple solution to avoid a kernel crash is to put the actual
+ * clock change in ROM and jump to that code from the kernel. The main
+ * disadvantage is that the ROM has to be modified, which is not
+ * possible on all SA-1100 platforms. Another disadvantage is that
+ * jumping to ROM makes clock switching unecessary complicated.
+ *
+ * The idea behind this driver is that the memory configuration can be
+ * changed while running from DRAM (even with interrupts turned on!)
+ * as long as all re-configuration steps yield a valid DRAM
+ * configuration. The advantages are clear: it will run on all SA-1100
+ * platforms, and the code is very simple.
+ *
+ * If you really want to understand what is going on in
+ * sa1100_update_dram_timings(), you'll have to read sections 8.2,
+ * 9.5.7.3, and 10.2 from the "Intel StrongARM SA-1100 Microprocessor
+ * Developers Manual" (available for free from Intel).
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/cpufreq.h>
+
+#include <asm/hardware.h>
+
+#include "generic.h"
+
+typedef struct {
+ int speed;
+ u32 mdcnfg;
+ u32 mdcas0;
+ u32 mdcas1;
+ u32 mdcas2;
+} sa1100_dram_regs_t;
+
+
+static struct cpufreq_driver sa1100_driver;
+
+static sa1100_dram_regs_t sa1100_dram_settings[] =
+{
+ /* speed, mdcnfg, mdcas0, mdcas1, mdcas2 clock frequency */
+ { 59000, 0x00dc88a3, 0xcccccccf, 0xfffffffc, 0xffffffff }, /* 59.0 MHz */
+ { 73700, 0x011490a3, 0xcccccccf, 0xfffffffc, 0xffffffff }, /* 73.7 MHz */
+ { 88500, 0x014e90a3, 0xcccccccf, 0xfffffffc, 0xffffffff }, /* 88.5 MHz */
+ { 103200, 0x01889923, 0xcccccccf, 0xfffffffc, 0xffffffff }, /* 103.2 MHz */
+ { 118000, 0x01c29923, 0x9999998f, 0xfffffff9, 0xffffffff }, /* 118.0 MHz */
+ { 132700, 0x01fb2123, 0x9999998f, 0xfffffff9, 0xffffffff }, /* 132.7 MHz */
+ { 147500, 0x02352123, 0x3333330f, 0xfffffff3, 0xffffffff }, /* 147.5 MHz */
+ { 162200, 0x026b29a3, 0x38e38e1f, 0xfff8e38e, 0xffffffff }, /* 162.2 MHz */
+ { 176900, 0x02a329a3, 0x71c71c1f, 0xfff1c71c, 0xffffffff }, /* 176.9 MHz */
+ { 191700, 0x02dd31a3, 0xe38e383f, 0xffe38e38, 0xffffffff }, /* 191.7 MHz */
+ { 206400, 0x03153223, 0xc71c703f, 0xffc71c71, 0xffffffff }, /* 206.4 MHz */
+ { 221200, 0x034fba23, 0xc71c703f, 0xffc71c71, 0xffffffff }, /* 221.2 MHz */
+ { 235900, 0x03853a23, 0xe1e1e07f, 0xe1e1e1e1, 0xffffffe1 }, /* 235.9 MHz */
+ { 250700, 0x03bf3aa3, 0xc3c3c07f, 0xc3c3c3c3, 0xffffffc3 }, /* 250.7 MHz */
+ { 265400, 0x03f7c2a3, 0xc3c3c07f, 0xc3c3c3c3, 0xffffffc3 }, /* 265.4 MHz */
+ { 280200, 0x0431c2a3, 0x878780ff, 0x87878787, 0xffffff87 }, /* 280.2 MHz */
+ { 0, 0, 0, 0, 0 } /* last entry */
+};
+
+static void sa1100_update_dram_timings(int current_speed, int new_speed)
+{
+ sa1100_dram_regs_t *settings = sa1100_dram_settings;
+
+ /* find speed */
+ while (settings->speed != 0) {
+ if(new_speed == settings->speed)
+ break;
+
+ settings++;
+ }
+
+ if (settings->speed == 0) {
+ panic("%s: couldn't find dram setting for speed %d\n",
+ __FUNCTION__, new_speed);
+ }
+
+ /* No risk, no fun: run with interrupts on! */
+ if (new_speed > current_speed) {
+ /* We're going FASTER, so first relax the memory
+ * timings before changing the core frequency
+ */
+
+ /* Half the memory access clock */
+ MDCNFG |= MDCNFG_CDB2;
+
+ /* The order of these statements IS important, keep 8
+ * pulses!!
+ */
+ MDCAS2 = settings->mdcas2;
+ MDCAS1 = settings->mdcas1;
+ MDCAS0 = settings->mdcas0;
+ MDCNFG = settings->mdcnfg;
+ } else {
+ /* We're going SLOWER: first decrease the core
+ * frequency and then tighten the memory settings.
+ */
+
+ /* Half the memory access clock */
+ MDCNFG |= MDCNFG_CDB2;
+
+ /* The order of these statements IS important, keep 8
+ * pulses!!
+ */
+ MDCAS0 = settings->mdcas0;
+ MDCAS1 = settings->mdcas1;
+ MDCAS2 = settings->mdcas2;
+ MDCNFG = settings->mdcnfg;
+ }
+}
+
+static int sa1100_target(struct cpufreq_policy *policy,
+ unsigned int target_freq,
+ unsigned int relation)
+{
+ unsigned int cur = sa11x0_getspeed(0);
+ unsigned int new_ppcr;
+
+ struct cpufreq_freqs freqs;
+ switch(relation){
+ case CPUFREQ_RELATION_L:
+ new_ppcr = sa11x0_freq_to_ppcr(target_freq);
+ if (sa11x0_ppcr_to_freq(new_ppcr) > policy->max)
+ new_ppcr--;
+ break;
+ case CPUFREQ_RELATION_H:
+ new_ppcr = sa11x0_freq_to_ppcr(target_freq);
+ if ((sa11x0_ppcr_to_freq(new_ppcr) > target_freq) &&
+ (sa11x0_ppcr_to_freq(new_ppcr - 1) >= policy->min))
+ new_ppcr--;
+ break;
+ }
+
+ freqs.old = cur;
+ freqs.new = sa11x0_ppcr_to_freq(new_ppcr);
+ freqs.cpu = 0;
+
+ cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
+
+ if (freqs.new > cur)
+ sa1100_update_dram_timings(cur, freqs.new);
+
+ PPCR = new_ppcr;
+
+ if (freqs.new < cur)
+ sa1100_update_dram_timings(cur, freqs.new);
+
+ cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+
+ return 0;
+}
+
+static int __init sa1100_cpu_init(struct cpufreq_policy *policy)
+{
+ if (policy->cpu != 0)
+ return -EINVAL;
+ policy->cur = policy->min = policy->max = sa11x0_getspeed(0);
+ policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
+ policy->cpuinfo.min_freq = 59000;
+ policy->cpuinfo.max_freq = 287000;
+ policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
+ return 0;
+}
+
+static struct cpufreq_driver sa1100_driver = {
+ .flags = CPUFREQ_STICKY,
+ .verify = sa11x0_verify_speed,
+ .target = sa1100_target,
+ .get = sa11x0_getspeed,
+ .init = sa1100_cpu_init,
+ .name = "sa1100",
+};
+
+static int __init sa1100_dram_init(void)
+{
+ if ((processor_id & CPU_SA1100_MASK) == CPU_SA1100_ID)
+ return cpufreq_register_driver(&sa1100_driver);
+ else
+ return -ENODEV;
+}
+
+arch_initcall(sa1100_dram_init);