drivers/cpufreq/sa1100-cpufreq.c - linux - Git at Google

 /*
  * 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
  *
  *
  * 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 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 target_freq,
 			 unsigned int relation)
 {
 	unsigned int cur = sa11x0_getspeed(0);
 	unsigned int new_ppcr;
 	struct cpufreq_freqs freqs;

 	new_ppcr = sa11x0_freq_to_ppcr(target_freq);
 	switch (relation) {
 	case CPUFREQ_RELATION_L:
 		if (sa11x0_ppcr_to_freq(new_ppcr) > policy->max)
 			new_ppcr--;
 		break;
 	case CPUFREQ_RELATION_H:
 		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);

 	cpufreq_notify_transition(policy, &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(policy, &freqs, CPUFREQ_POSTCHANGE);

 	return 0;
 }

 static int __init sa1100_cpu_init(struct cpufreq_policy *policy)
 {
 	if (policy->cpu != 0)
 		return -EINVAL;
 	policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;

 	return cpufreq_table_validate_and_show(policy, sa11x0_freq_table);
 }

 static struct cpufreq_driver sa1100_driver __refdata = {
 	.flags		= CPUFREQ_STICKY,
 	.verify		= cpufreq_generic_frequency_table_verify,
 	.target		= 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);
	/*
	* 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
	*
	*
	* 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 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 target_freq,
	unsigned int relation)
	{
	unsigned int cur = sa11x0_getspeed(0);
	unsigned int new_ppcr;
	struct cpufreq_freqs freqs;

	new_ppcr = sa11x0_freq_to_ppcr(target_freq);
	switch (relation) {
	case CPUFREQ_RELATION_L:
	if (sa11x0_ppcr_to_freq(new_ppcr) > policy->max)
	new_ppcr--;
	break;
	case CPUFREQ_RELATION_H:
	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);

	cpufreq_notify_transition(policy, &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(policy, &freqs, CPUFREQ_POSTCHANGE);

	return 0;
	}

	static int __init sa1100_cpu_init(struct cpufreq_policy *policy)
	{
	if (policy->cpu != 0)
	return -EINVAL;
	policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;

	return cpufreq_table_validate_and_show(policy, sa11x0_freq_table);
	}

	static struct cpufreq_driver sa1100_driver __refdata = {
	.flags = CPUFREQ_STICKY,
	.verify = cpufreq_generic_frequency_table_verify,
	.target = 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);