cpu-sa1100.c

上传linux-jx2410的源代码

/*
 * cpu-sa1100.c: clock scaling for the SA1100
 *
 * Copyright (C) 2000 2001, The Delft University of Technology
 *
 * Authors: 
 * - Johan Pouwelse ([e-mail]): initial version
 * - Erik Mouw ([e-mail]):
 *   - 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>

extern unsigned int sa11x0_freq_to_ppcr(unsigned int khz);
extern unsigned int sa11x0_validatespeed(unsigned int khz);


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 void sa1100_setspeed(unsigned int khz)
{
	PPCR = sa11x0_freq_to_ppcr(khz);
}

static int __init sa1100_dram_init(void)
{
	int ret = -ENODEV;

	if ((processor_id & CPU_SA1100_MASK) == CPU_SA1100_ID) {
		ret = cpufreq_register_notifier(&sa1100_dram_block);

		cpufreq_setfunctions(sa11x0_validatespeed, sa1100_setspeed);
	}

	return ret;
}

__initcall(sa1100_dram_init);