+++ /dev/null
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * 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.lartmaker.nl/), which is
- * sponsored by the Mobile Multi-media Communications
- * (http://www.mobimedia.org/) 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
- *
- * 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 unnecessary 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 <linux/io.h>
-
-#include <asm/cputype.h>
-
-#include <mach/generic.h>
-#include <mach/hardware.h>
-
-struct sa1100_dram_regs {
- int speed;
- u32 mdcnfg;
- u32 mdcas0;
- u32 mdcas1;
- u32 mdcas2;
-};
-
-
-static struct cpufreq_driver sa1100_driver;
-
-static struct sa1100_dram_regs sa1100_dram_settings[] = {
- /*speed, mdcnfg, mdcas0, mdcas1, mdcas2, clock freq */
- { 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)
-{
- struct sa1100_dram_regs *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",
- __func__, 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 ppcr)
-{
- unsigned int cur = sa11x0_getspeed(0);
- unsigned int new_freq;
-
- new_freq = sa11x0_freq_table[ppcr].frequency;
-
- if (new_freq > cur)
- sa1100_update_dram_timings(cur, new_freq);
-
- PPCR = ppcr;
-
- if (new_freq < cur)
- sa1100_update_dram_timings(cur, new_freq);
-
- return 0;
-}
-
-static int __init sa1100_cpu_init(struct cpufreq_policy *policy)
-{
- cpufreq_generic_init(policy, sa11x0_freq_table, 0);
- return 0;
-}
-
-static struct cpufreq_driver sa1100_driver __refdata = {
- .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK |
- CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING,
- .verify = cpufreq_generic_frequency_table_verify,
- .target_index = sa1100_target,
- .get = sa11x0_getspeed,
- .init = sa1100_cpu_init,
- .name = "sa1100",
-};
-
-static int __init sa1100_dram_init(void)
-{
- if (cpu_is_sa1100())
- return cpufreq_register_driver(&sa1100_driver);
- else
- return -ENODEV;
-}
-
-arch_initcall(sa1100_dram_init);
projects / platform / kernel / linux-rpi.git / commitdiff