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// 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);
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