gx-suspmod.c

linux-2.6.15.6

/*
 *	Cyrix MediaGX and NatSemi Geode Suspend Modulation
 *	(C) 2002 Zwane Mwaikambo <[e-mail]>
 *	(C) 2002 Hiroshi Miura   <[e-mail]>
 *	All Rights Reserved
 *
 *	This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      version 2 as published by the Free Software Foundation 
 *
 *      The author(s) of this software shall not be held liable for damages
 *      of any nature resulting due to the use of this software. This
 *      software is provided AS-IS with no warranties.
 *	
 * Theoritical note:
 *
 *	(see Geode(tm) CS5530 manual (rev.4.1) page.56)
 *
 *	CPU frequency control on NatSemi Geode GX1/GXLV processor and CS55x0
 *	are based on Suspend Moduration.
 *
 *	Suspend Modulation works by asserting and de-asserting the SUSP# pin
 *	to CPU(GX1/GXLV) for configurable durations. When asserting SUSP#
 *	the CPU enters an idle state. GX1 stops its core clock when SUSP# is 
 *	asserted then power consumption is reduced.
 *
 *	Suspend Modulation's OFF/ON duration are configurable 
 *	with 'Suspend Modulation OFF Count Register'
 *	and 'Suspend Modulation ON Count Register'.
 *	These registers are 8bit counters that represent the number of 
 *	32us intervals which the SUSP# pin is asserted(ON)/de-asserted(OFF)
 *	to the processor.
 *
 *	These counters define a ratio which is the effective frequency 
 * 	of operation of the system.
 *
 *			       OFF Count
 *	F_eff = Fgx * ----------------------
 *	                OFF Count + ON Count
 *
 *	0 <= On Count, Off Count <= 255
 *
 *	From these limits, we can get register values 
 *
 *	off_duration + on_duration <= MAX_DURATION
 *	on_duration = off_duration * (stock_freq - freq) / freq
 *
 *      off_duration  =  (freq * DURATION) / stock_freq 
 *      on_duration = DURATION - off_duration 
 *
 *
 *---------------------------------------------------------------------------
 *
 * ChangeLog:
 *  	Dec. 12, 2003	Hiroshi Miura <[e-mail]>
 *  		- fix on/off register mistake
 *  		- fix cpu_khz calc when it stops cpu modulation.
 *
 *	Dec. 11, 2002 	Hiroshi Miura <[e-mail]>
 *		- rewrite for Cyrix MediaGX Cx5510/5520 and 
 *		  NatSemi Geode Cs5530(A).
 *
 *	Jul. ??, 2002  Zwane Mwaikambo <[e-mail]>
 *		- cs5530_mod patch for 2.4.19-rc1.
 *
 *---------------------------------------------------------------------------
 *
 * Todo
 *	Test on machines with 5510, 5530, 5530A
 */

/************************************************************************
 *			Suspend Modulation - Definitions		*
 ************************************************************************/

#include <linux/kernel.h>
#include <linux/module.h> 
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/cpufreq.h>
#include <linux/pci.h>
#include <asm/processor.h> 
#include <asm/errno.h>

/* PCI config registers, all at F0 */
#define PCI_PMER1              0x80    /* power management enable register 1 */
#define PCI_PMER2              0x81    /* power management enable register 2 */
#define PCI_PMER3              0x82    /* power management enable register 3 */
#define PCI_IRQTC              0x8c    /* irq speedup timer counter register:typical 2 to 4ms */
#define PCI_VIDTC              0x8d    /* video speedup timer counter register: typical 50 to 100ms */
#define PCI_MODOFF             0x94    /* suspend modulation OFF counter register, 1 = 32us */
#define PCI_MODON              0x95    /* suspend modulation ON counter register */
#define PCI_SUSCFG             0x96    /* suspend configuration register */

/* PMER1 bits */
#define GPM                    (1<<0)  /* global power management */
#define GIT                    (1<<1)  /* globally enable PM device idle timers */
#define GTR                    (1<<2)  /* globally enable IO traps */
#define IRQ_SPDUP              (1<<3)  /* disable clock throttle during interrupt handling */
#define VID_SPDUP              (1<<4)  /* disable clock throttle during vga video handling */

/* SUSCFG bits */
#define SUSMOD                 (1<<0)  /* enable/disable suspend modulation */
/* the belows support only with cs5530 (after rev.1.2)/cs5530A */ 
#define SMISPDUP               (1<<1)  /* select how SMI re-enable suspend modulation: */
                                       /* IRQTC timer or read SMI speedup disable reg.(F1BAR[08-09h]) */
#define SUSCFG                 (1<<2)  /* enable powering down a GXLV processor. "Special 3Volt Suspend" mode */
/* the belows support only with cs5530A */ 
#define PWRSVE_ISA             (1<<3)  /* stop ISA clock  */
#define PWRSVE                 (1<<4)  /* active idle */

struct gxfreq_params {
	u8 on_duration;
	u8 off_duration;
	u8 pci_suscfg;
	u8 pci_pmer1;
	u8 pci_pmer2;
	u8 pci_rev;
	struct pci_dev *cs55x0;
};

static struct gxfreq_params *gx_params;
static int stock_freq;

/* PCI bus clock - defaults to 30.000 if cpu_khz is not available */
static int pci_busclk = 0;
module_param (pci_busclk, int, 0444);

/* maximum duration for which the cpu may be suspended
 * (32us * MAX_DURATION). If no parameter is given, this defaults
 * to 255. 
 * Note that this leads to a maximum of 8 ms(!) where the CPU clock
 * is suspended -- processing power is just 0.39% of what it used to be,
 * though. 781.25 kHz(!) for a 200 MHz processor -- wow. */
static int max_duration = 255;
module_param (max_duration, int, 0444);

/* For the default policy, we want at least some processing power
 * - let's say 5%. (min = maxfreq / POLICY_MIN_DIV)
 */
#define POLICY_MIN_DIV 20


#define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "gx-suspmod", msg)

/**
 *      we can detect a core multipiler from dir0_lsb 
 *      from GX1 datasheet p.56, 
 *	   MULT[3:0]:
 *	   0000 = SYSCLK multiplied by 4 (test only)
 *	   0001 = SYSCLK multiplied by 10
 *	   0010 = SYSCLK multiplied by 4
 *	   0011 = SYSCLK multiplied by 6
 *	   0100 = SYSCLK multiplied by 9
 *	   0101 = SYSCLK multiplied by 5
 *	   0110 = SYSCLK multiplied by 7
 *	   0111 = SYSCLK multiplied by 8
 *              of 33.3MHz
 **/
static int gx_freq_mult[16] = {
		4, 10, 4, 6, 9, 5, 7, 8,
		0, 0, 0, 0, 0, 0, 0, 0
};


/****************************************************************
 * 	Low Level chipset interface				*
 ****************************************************************/
static struct pci_device_id gx_chipset_tbl[] __initdata = {
        { PCI_VENDOR_ID_CYRIX, PCI_DEVICE_ID_CYRIX_5530_LEGACY, PCI_ANY_ID, PCI_ANY_ID },
        { PCI_VENDOR_ID_CYRIX, PCI_DEVICE_ID_CYRIX_5520, PCI_ANY_ID, PCI_ANY_ID },
        { PCI_VENDOR_ID_CYRIX, PCI_DEVICE_ID_CYRIX_5510, PCI_ANY_ID, PCI_ANY_ID },
        { 0, },
};

/**
 *     gx_detect_chipset:
 *
 **/
static __init struct pci_dev *gx_detect_chipset(void)
{
	struct pci_dev *gx_pci = NULL;

	/* check if CPU is a MediaGX or a Geode. */
        if ((current_cpu_data.x86_vendor != X86_VENDOR_NSC) && 
	    (current_cpu_data.x86_vendor != X86_VENDOR_CYRIX)) {
		dprintk("error: no MediaGX/Geode processor found!\n");
		return NULL;		
	}

	/* detect which companion chip is used */
	while ((gx_pci = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, gx_pci)) != NULL) {
		if ((pci_match_id(gx_chipset_tbl, gx_pci)) != NULL) {
			return gx_pci;
		}
	}

	dprintk("error: no supported chipset found!\n");
	return NULL;
}

/**
 *      gx_get_cpuspeed:
 *
 * Finds out at which efficient frequency the Cyrix MediaGX/NatSemi Geode CPU runs.
 */
static unsigned int gx_get_cpuspeed(unsigned int cpu)
{
	if ((gx_params->pci_suscfg & SUSMOD) == 0) 
		return stock_freq;

	return (stock_freq * gx_params->off_duration) 
		/ (gx_params->on_duration + gx_params->off_duration);
}

/**
 *      gx_validate_speed:
 *      determine current cpu speed
 *       
**/

static unsigned int gx_validate_speed(unsigned int khz, u8 *on_duration, u8 *off_duration)
{
	unsigned int i;
	u8 tmp_on, tmp_off;
	int old_tmp_freq = stock_freq;
	int tmp_freq;

	*off_duration=1;
	*on_duration=0;

	for (i=max_duration; i>0; i--) {
		tmp_off = ((khz * i) / stock_freq) & 0xff; 
		tmp_on = i - tmp_off;
		tmp_freq = (stock_freq * tmp_off) / i;
		/* if this relation is closer to khz, use this. If it's equal,
		 * prefer it, too - lower latency */
		if (abs(tmp_freq - khz) <= abs(old_tmp_freq - khz)) {
			*on_duration = tmp_on;
			*off_duration = tmp_off;
			old_tmp_freq = tmp_freq;
		}
	}

	return old_tmp_freq;
}


/**
 * 	gx_set_cpuspeed:
 *		set cpu speed in khz.
 **/