/* * 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 #include #include #include #include typedef struct { int speed; u32 mdcnfg; u32 mdcas0; u32 mdcas1; u32 mdcas2; } sa1100_dram_regs_t; static sa1100_dram_regs_t sa1100_dram_settings[] = { /* { 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_dram_notifier(struct notifier_block *nb, unsigned long val, void *data) { struct cpufreq_info *ci = data; switch(val) { case CPUFREQ_MINMAX: cpufreq_updateminmax(data, sa1100_dram_settings->speed, -1); break; case CPUFREQ_PRECHANGE: if(ci->new_freq > ci->old_freq) sa1100_update_dram_timings(ci->old_freq, ci->new_freq); break; case CPUFREQ_POSTCHANGE: if(ci->new_freq < ci->old_freq) sa1100_update_dram_timings(ci->old_freq, ci->new_freq); break; default: printk(KERN_INFO "%s: ignoring unknown notifier type (%ld)\n", __FUNCTION__, val); } return 0; } static struct notifier_block sa1100_dram_block = { notifier_call: sa1100_dram_notifier, }; static int __init sa1100_dram_init(void) { return cpufreq_register_notifier(&sa1100_dram_block); } __initcall(sa1100_dram_init);