arch/arm/mach-omap2/voltage.c

/*
 * OMAP3/OMAP4 Voltage Management Routines
 *
 * Author: Thara Gopinath	<thara@ti.com>
 *
 * Copyright (C) 2007 Texas Instruments, Inc.
 * Rajendra Nayak <rnayak@ti.com>
 * Lesly A M <x0080970@ti.com>
 *
 * Copyright (C) 2008, 2011 Nokia Corporation
 * Kalle Jokiniemi
 * Paul Walmsley
 *
 * Copyright (C) 2010 Texas Instruments, Inc.
 * Thara Gopinath <thara@ti.com>
 *
 * 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.
 */

#include <linux/delay.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/debugfs.h>
#include <linux/slab.h>

#include <plat/common.h>

#include "prm-regbits-34xx.h"
#include "prm-regbits-44xx.h"
#include "prm44xx.h"
#include "prcm44xx.h"
#include "prminst44xx.h"
#include "control.h"

#include "voltage.h"
#include "powerdomain.h"

#include "vc.h"
#include "vp.h"

static LIST_HEAD(voltdm_list);

#define VOLTAGE_DIR_SIZE	16
static struct dentry *voltage_dir;

/* Init function pointers */
static int vp_forceupdate_scale_voltage(struct voltagedomain *voltdm,
					unsigned long target_volt);

static u32 omap3_voltage_read_reg(u16 mod, u8 offset)
{
	return omap2_prm_read_mod_reg(mod, offset);
}

static void omap3_voltage_write_reg(u32 val, u16 mod, u8 offset)
{
	omap2_prm_write_mod_reg(val, mod, offset);
}

static u32 omap4_voltage_read_reg(u16 mod, u8 offset)
{
	return omap4_prminst_read_inst_reg(OMAP4430_PRM_PARTITION,
					mod, offset);
}

static void omap4_voltage_write_reg(u32 val, u16 mod, u8 offset)
{
	omap4_prminst_write_inst_reg(val, OMAP4430_PRM_PARTITION, mod, offset);
}

static int __init _config_common_vdd_data(struct voltagedomain *voltdm)
{
	char *sys_ck_name;
	struct clk *sys_ck;
	u32 sys_clk_speed, timeout_val, waittime;
	struct omap_vdd_info *vdd = voltdm->vdd;

	/*
	 * XXX Clockfw should handle this, or this should be in a
	 * struct record
	 */
	if (cpu_is_omap24xx() || cpu_is_omap34xx())
		sys_ck_name = "sys_ck";
	else if (cpu_is_omap44xx())
		sys_ck_name = "sys_clkin_ck";
	else
		return -EINVAL;

	/*
	 * Sys clk rate is require to calculate vp timeout value and
	 * smpswaittimemin and smpswaittimemax.
	 */
	sys_ck = clk_get(NULL, sys_ck_name);
	if (IS_ERR(sys_ck)) {
		pr_warning("%s: Could not get the sys clk to calculate"
			"various vdd_%s params\n", __func__, voltdm->name);
		return -EINVAL;
	}
	sys_clk_speed = clk_get_rate(sys_ck);
	clk_put(sys_ck);
	/* Divide to avoid overflow */
	sys_clk_speed /= 1000;

	/* Generic voltage parameters */
	vdd->volt_scale = vp_forceupdate_scale_voltage;
	vdd->vp_enabled = false;

	vdd->vp_rt_data.vpconfig_erroroffset =
		(vdd->pmic_info->vp_erroroffset <<
		 vdd->vp_data->vp_common->vpconfig_erroroffset_shift);

	timeout_val = (sys_clk_speed * vdd->pmic_info->vp_timeout_us) / 1000;
	vdd->vp_rt_data.vlimitto_timeout = timeout_val;
	vdd->vp_rt_data.vlimitto_vddmin = vdd->pmic_info->vp_vddmin;
	vdd->vp_rt_data.vlimitto_vddmax = vdd->pmic_info->vp_vddmax;

	waittime = ((vdd->pmic_info->step_size / vdd->pmic_info->slew_rate) *
				sys_clk_speed) / 1000;
	vdd->vp_rt_data.vstepmin_smpswaittimemin = waittime;
	vdd->vp_rt_data.vstepmax_smpswaittimemax = waittime;
	vdd->vp_rt_data.vstepmin_stepmin = vdd->pmic_info->vp_vstepmin;
	vdd->vp_rt_data.vstepmax_stepmax = vdd->pmic_info->vp_vstepmax;

	return 0;
}

/* Voltage debugfs support */
static int vp_volt_debug_get(void *data, u64 *val)
{
	struct voltagedomain *voltdm = (struct voltagedomain *)data;
	struct omap_vdd_info *vdd = voltdm->vdd;
	u8 vsel;

	if (!vdd) {
		pr_warning("Wrong paramater passed\n");
		return -EINVAL;
	}

	vsel = vdd->read_reg(vdd->vp_data->vp_common->prm_mod, vdd->vp_data->voltage);

	if (!vdd->pmic_info->vsel_to_uv) {
		pr_warning("PMIC function to convert vsel to voltage"
			"in uV not registerd\n");
		return -EINVAL;
	}

	*val = vdd->pmic_info->vsel_to_uv(vsel);
	return 0;
}

static int nom_volt_debug_get(void *data, u64 *val)
{
	struct voltagedomain *voltdm = (struct voltagedomain *)data;

	if (!voltdm) {
		pr_warning("Wrong paramater passed\n");
		return -EINVAL;
	}

	*val = omap_voltage_get_nom_volt(voltdm);

	return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(vp_volt_debug_fops, vp_volt_debug_get, NULL, "%llu\n");
DEFINE_SIMPLE_ATTRIBUTE(nom_volt_debug_fops, nom_volt_debug_get, NULL,
								"%llu\n");
static void vp_latch_vsel(struct voltagedomain *voltdm)
{
	u32 vpconfig;
	unsigned long uvdc;
	char vsel;
	struct omap_vdd_info *vdd = voltdm->vdd;

	uvdc = omap_voltage_get_nom_volt(voltdm);
	if (!uvdc) {
		pr_warning("%s: unable to find current voltage for vdd_%s\n",
			__func__, voltdm->name);
		return;
	}

	if (!vdd->pmic_info || !vdd->pmic_info->uv_to_vsel) {
		pr_warning("%s: PMIC function to convert voltage in uV to"
			" vsel not registered\n", __func__);
		return;
	}

	vsel = vdd->pmic_info->uv_to_vsel(uvdc);

	vpconfig = vdd->read_reg(vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);
	vpconfig &= ~(vdd->vp_data->vp_common->vpconfig_initvoltage_mask |
			vdd->vp_data->vp_common->vpconfig_initvdd);
	vpconfig |= vsel << vdd->vp_data->vp_common->vpconfig_initvoltage_shift;

	vdd->write_reg(vpconfig, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);

	/* Trigger initVDD value copy to voltage processor */
	vdd->write_reg((vpconfig | vdd->vp_data->vp_common->vpconfig_initvdd),
		       vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);

	/* Clear initVDD copy trigger bit */
	vdd->write_reg(vpconfig, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);
}

/* Generic voltage init functions */
static void __init vp_init(struct voltagedomain *voltdm)
{
	struct omap_vdd_info *vdd = voltdm->vdd;
	u32 vp_val;

	if (!vdd->read_reg || !vdd->write_reg) {
		pr_err("%s: No read/write API for accessing vdd_%s regs\n",
			__func__, voltdm->name);
		return;
	}

	vp_val = vdd->vp_rt_data.vpconfig_erroroffset |
		(vdd->vp_rt_data.vpconfig_errorgain <<
		vdd->vp_data->vp_common->vpconfig_errorgain_shift) |
		vdd->vp_data->vp_common->vpconfig_timeouten;
	vdd->write_reg(vp_val, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);

	vp_val = ((vdd->vp_rt_data.vstepmin_smpswaittimemin <<
		vdd->vp_data->vp_common->vstepmin_smpswaittimemin_shift) |
		(vdd->vp_rt_data.vstepmin_stepmin <<
		vdd->vp_data->vp_common->vstepmin_stepmin_shift));
	vdd->write_reg(vp_val, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vstepmin);

	vp_val = ((vdd->vp_rt_data.vstepmax_smpswaittimemax <<
		vdd->vp_data->vp_common->vstepmax_smpswaittimemax_shift) |
		(vdd->vp_rt_data.vstepmax_stepmax <<
		vdd->vp_data->vp_common->vstepmax_stepmax_shift));
	vdd->write_reg(vp_val, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vstepmax);

	vp_val = ((vdd->vp_rt_data.vlimitto_vddmax <<
		vdd->vp_data->vp_common->vlimitto_vddmax_shift) |
		(vdd->vp_rt_data.vlimitto_vddmin <<
		vdd->vp_data->vp_common->vlimitto_vddmin_shift) |
		(vdd->vp_rt_data.vlimitto_timeout <<
		vdd->vp_data->vp_common->vlimitto_timeout_shift));
	vdd->write_reg(vp_val, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vlimitto);
}

static void __init vdd_debugfs_init(struct voltagedomain *voltdm)
{
	char *name;
	struct omap_vdd_info *vdd = voltdm->vdd;

	name = kzalloc(VOLTAGE_DIR_SIZE, GFP_KERNEL);
	if (!name) {
		pr_warning("%s: Unable to allocate memory for debugfs"
			" directory name for vdd_%s",
			__func__, voltdm->name);
		return;
	}
	strcpy(name, "vdd_");
	strcat(name, voltdm->name);

	vdd->debug_dir = debugfs_create_dir(name, voltage_dir);
	kfree(name);
	if (IS_ERR(vdd->debug_dir)) {
		pr_warning("%s: Unable to create debugfs directory for"
			" vdd_%s\n", __func__, voltdm->name);
		vdd->debug_dir = NULL;
		return;
	}

	(void) debugfs_create_x16("vp_errorgain", S_IRUGO, vdd->debug_dir,
				&(vdd->vp_rt_data.vpconfig_errorgain));
	(void) debugfs_create_x16("vp_smpswaittimemin", S_IRUGO,
				vdd->debug_dir,
				&(vdd->vp_rt_data.vstepmin_smpswaittimemin));
	(void) debugfs_create_x8("vp_stepmin", S_IRUGO, vdd->debug_dir,
				&(vdd->vp_rt_data.vstepmin_stepmin));
	(void) debugfs_create_x16("vp_smpswaittimemax", S_IRUGO,
				vdd->debug_dir,
				&(vdd->vp_rt_data.vstepmax_smpswaittimemax));
	(void) debugfs_create_x8("vp_stepmax", S_IRUGO, vdd->debug_dir,
				&(vdd->vp_rt_data.vstepmax_stepmax));
	(void) debugfs_create_x8("vp_vddmax", S_IRUGO, vdd->debug_dir,
				&(vdd->vp_rt_data.vlimitto_vddmax));
	(void) debugfs_create_x8("vp_vddmin", S_IRUGO, vdd->debug_dir,
				&(vdd->vp_rt_data.vlimitto_vddmin));
	(void) debugfs_create_x16("vp_timeout", S_IRUGO, vdd->debug_dir,
				&(vdd->vp_rt_data.vlimitto_timeout));
	(void) debugfs_create_file("curr_vp_volt", S_IRUGO, vdd->debug_dir,
				(void *) voltdm, &vp_volt_debug_fops);
	(void) debugfs_create_file("curr_nominal_volt", S_IRUGO,
				vdd->debug_dir, (void *) voltdm,
				&nom_volt_debug_fops);
}

/* VP force update method of voltage scaling */
static int vp_forceupdate_scale_voltage(struct voltagedomain *voltdm,
		unsigned long target_volt)
{
	struct omap_vdd_info *vdd = voltdm->vdd;
	u32 vpconfig;
	u8 target_vsel, current_vsel;
	int ret, timeout = 0;

	ret = omap_vc_pre_scale(voltdm, target_volt, &target_vsel, &current_vsel);
	if (ret)
		return ret;

	/*
	 * Clear all pending TransactionDone interrupt/status. Typical latency
	 * is <3us
	 */
	while (timeout++ < VP_TRANXDONE_TIMEOUT) {
		vdd->write_reg(vdd->vp_data->prm_irqst_data->tranxdone_status,
			       vdd->prm_irqst_mod, vdd->prm_irqst_reg);
		if (!(vdd->read_reg(vdd->prm_irqst_mod, vdd->prm_irqst_reg) &
		      vdd->vp_data->prm_irqst_data->tranxdone_status))
			break;
		udelay(1);
	}
	if (timeout >= VP_TRANXDONE_TIMEOUT) {
		pr_warning("%s: vdd_%s TRANXDONE timeout exceeded."
			"Voltage change aborted", __func__, voltdm->name);
		return -ETIMEDOUT;
	}

	/* Configure for VP-Force Update */
	vpconfig = vdd->read_reg(vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);
	vpconfig &= ~(vdd->vp_data->vp_common->vpconfig_initvdd |
			vdd->vp_data->vp_common->vpconfig_forceupdate |
			vdd->vp_data->vp_common->vpconfig_initvoltage_mask);
	vpconfig |= ((target_vsel <<
			vdd->vp_data->vp_common->vpconfig_initvoltage_shift));
	vdd->write_reg(vpconfig, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);

	/* Trigger initVDD value copy to voltage processor */
	vpconfig |= vdd->vp_data->vp_common->vpconfig_initvdd;
	vdd->write_reg(vpconfig, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);

	/* Force update of voltage */
	vpconfig |= vdd->vp_data->vp_common->vpconfig_forceupdate;
	vdd->write_reg(vpconfig, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);

	/*
	 * Wait for TransactionDone. Typical latency is <200us.
	 * Depends on SMPSWAITTIMEMIN/MAX and voltage change
	 */
	timeout = 0;
	omap_test_timeout((vdd->read_reg(vdd->prm_irqst_mod,
					 vdd->prm_irqst_reg) &
			   vdd->vp_data->prm_irqst_data->tranxdone_status),
			  VP_TRANXDONE_TIMEOUT, timeout);
	if (timeout >= VP_TRANXDONE_TIMEOUT)
		pr_err("%s: vdd_%s TRANXDONE timeout exceeded."
			"TRANXDONE never got set after the voltage update\n",
			__func__, voltdm->name);

	omap_vc_post_scale(voltdm, target_volt, target_vsel, current_vsel);

	/*
	 * Disable TransactionDone interrupt , clear all status, clear
	 * control registers
	 */
	timeout = 0;
	while (timeout++ < VP_TRANXDONE_TIMEOUT) {
		vdd->write_reg(vdd->vp_data->prm_irqst_data->tranxdone_status,
			       vdd->prm_irqst_mod, vdd->prm_irqst_reg);
		if (!(vdd->read_reg(vdd->prm_irqst_mod, vdd->prm_irqst_reg) &
		      vdd->vp_data->prm_irqst_data->tranxdone_status))
			break;
		udelay(1);
	}

	if (timeout >= VP_TRANXDONE_TIMEOUT)
		pr_warning("%s: vdd_%s TRANXDONE timeout exceeded while trying"
			"to clear the TRANXDONE status\n",
			__func__, voltdm->name);

	vpconfig = vdd->read_reg(vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);
	/* Clear initVDD copy trigger bit */
	vpconfig &= ~vdd->vp_data->vp_common->vpconfig_initvdd;
	vdd->write_reg(vpconfig, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);
	/* Clear force bit */
	vpconfig &= ~vdd->vp_data->vp_common->vpconfig_forceupdate;
	vdd->write_reg(vpconfig, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);

	return 0;
}

static int __init omap_vdd_data_configure(struct voltagedomain *voltdm)
{
	struct omap_vdd_info *vdd = voltdm->vdd;
	int ret = -EINVAL;

	if (!vdd->pmic_info) {
		pr_err("%s: PMIC info requried to configure vdd_%s not"
			"populated.Hence cannot initialize vdd_%s\n",
			__func__, voltdm->name, voltdm->name);
		goto ovdc_out;
	}

	if (IS_ERR_VALUE(_config_common_vdd_data(voltdm)))
		goto ovdc_out;

	if (cpu_is_omap34xx()) {
		vdd->read_reg = omap3_voltage_read_reg;
		vdd->write_reg = omap3_voltage_write_reg;
		ret = 0;
	} else if (cpu_is_omap44xx()) {
		vdd->read_reg = omap4_voltage_read_reg;
		vdd->write_reg = omap4_voltage_write_reg;
		ret = 0;
	}

ovdc_out:
	return ret;
}

/* Public functions */
/**
 * omap_voltage_get_nom_volt() - Gets the current non-auto-compensated voltage
 * @voltdm:	pointer to the VDD for which current voltage info is needed
 *
 * API to get the current non-auto-compensated voltage for a VDD.
 * Returns 0 in case of error else returns the current voltage for the VDD.
 */
unsigned long omap_voltage_get_nom_volt(struct voltagedomain *voltdm)
{
	struct omap_vdd_info *vdd;

	if (!voltdm || IS_ERR(voltdm)) {
		pr_warning("%s: VDD specified does not exist!\n", __func__);
		return 0;
	}

	vdd = voltdm->vdd;

	return vdd->curr_volt;
}

/**
 * omap_vp_get_curr_volt() - API to get the current vp voltage.
 * @voltdm:	pointer to the VDD.
 *
 * This API returns the current voltage for the specified voltage processor
 */
unsigned long omap_vp_get_curr_volt(struct voltagedomain *voltdm)
{
	struct omap_vdd_info *vdd;
	u8 curr_vsel;

	if (!voltdm || IS_ERR(voltdm)) {
		pr_warning("%s: VDD specified does not exist!\n", __func__);
		return 0;
	}

	vdd = voltdm->vdd;
	if (!vdd->read_reg) {
		pr_err("%s: No read API for reading vdd_%s regs\n",
			__func__, voltdm->name);
		return 0;
	}

	curr_vsel = vdd->read_reg(vdd->vp_data->vp_common->prm_mod, vdd->vp_data->voltage);

	if (!vdd->pmic_info || !vdd->pmic_info->vsel_to_uv) {
		pr_warning("%s: PMIC function to convert vsel to voltage"
			"in uV not registerd\n", __func__);
		return 0;
	}

	return vdd->pmic_info->vsel_to_uv(curr_vsel);
}

/**
 * omap_vp_enable() - API to enable a particular VP
 * @voltdm:	pointer to the VDD whose VP is to be enabled.
 *
 * This API enables a particular voltage processor. Needed by the smartreflex
 * class drivers.
 */
void omap_vp_enable(struct voltagedomain *voltdm)
{
	struct omap_vdd_info *vdd;
	u32 vpconfig;

	if (!voltdm || IS_ERR(voltdm)) {
		pr_warning("%s: VDD specified does not exist!\n", __func__);
		return;
	}

	vdd = voltdm->vdd;
	if (!vdd->read_reg || !vdd->write_reg) {
		pr_err("%s: No read/write API for accessing vdd_%s regs\n",
			__func__, voltdm->name);
		return;
	}

	/* If VP is already enabled, do nothing. Return */
	if (vdd->vp_enabled)
		return;

	vp_latch_vsel(voltdm);

	/* Enable VP */
	vpconfig = vdd->read_reg(vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);
	vpconfig |= vdd->vp_data->vp_common->vpconfig_vpenable;
	vdd->write_reg(vpconfig, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);
	vdd->vp_enabled = true;
}

/**
 * omap_vp_disable() - API to disable a particular VP
 * @voltdm:	pointer to the VDD whose VP is to be disabled.
 *
 * This API disables a particular voltage processor. Needed by the smartreflex
 * class drivers.
 */
void omap_vp_disable(struct voltagedomain *voltdm)
{
	struct omap_vdd_info *vdd;
	u32 vpconfig;
	int timeout;

	if (!voltdm || IS_ERR(voltdm)) {
		pr_warning("%s: VDD specified does not exist!\n", __func__);
		return;
	}

	vdd = voltdm->vdd;
	if (!vdd->read_reg || !vdd->write_reg) {
		pr_err("%s: No read/write API for accessing vdd_%s regs\n",
			__func__, voltdm->name);
		return;
	}

	/* If VP is already disabled, do nothing. Return */
	if (!vdd->vp_enabled) {
		pr_warning("%s: Trying to disable VP for vdd_%s when"
			"it is already disabled\n", __func__, voltdm->name);
		return;
	}

	/* Disable VP */
	vpconfig = vdd->read_reg(vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);
	vpconfig &= ~vdd->vp_data->vp_common->vpconfig_vpenable;
	vdd->write_reg(vpconfig, vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vpconfig);

	/*
	 * Wait for VP idle Typical latency is <2us. Maximum latency is ~100us
	 */
	omap_test_timeout((vdd->read_reg(vdd->vp_data->vp_common->prm_mod, vdd->vp_data->vstatus)),
				VP_IDLE_TIMEOUT, timeout);

	if (timeout >= VP_IDLE_TIMEOUT)
		pr_warning("%s: vdd_%s idle timedout\n",
			__func__, voltdm->name);

	vdd->vp_enabled = false;

	return;
}

/**
 * omap_voltage_scale_vdd() - API to scale voltage of a particular
 *				voltage domain.
 * @voltdm:	pointer to the VDD which is to be scaled.
 * @target_volt:	The target voltage of the voltage domain
 *
 * This API should be called by the kernel to do the voltage scaling
 * for a particular voltage domain during dvfs or any other situation.
 */
int omap_voltage_scale_vdd(struct voltagedomain *voltdm,
		unsigned long target_volt)
{
	struct omap_vdd_info *vdd;

	if (!voltdm || IS_ERR(voltdm)) {
		pr_warning("%s: VDD specified does not exist!\n", __func__);
		return -EINVAL;
	}

	vdd = voltdm->vdd;

	if (!vdd->volt_scale) {
		pr_err("%s: No voltage scale API registered for vdd_%s\n",
			__func__, voltdm->name);
		return -ENODATA;
	}

	return vdd->volt_scale(voltdm, target_volt);
}

/**
 * omap_voltage_reset() - Resets the voltage of a particular voltage domain
 *			to that of the current OPP.
 * @voltdm:	pointer to the VDD whose voltage is to be reset.
 *
 * This API finds out the correct voltage the voltage domain is supposed
 * to be at and resets the voltage to that level. Should be used especially
 * while disabling any voltage compensation modules.
 */
void omap_voltage_reset(struct voltagedomain *voltdm)
{
	unsigned long target_uvdc;

	if (!voltdm || IS_ERR(voltdm)) {
		pr_warning("%s: VDD specified does not exist!\n", __func__);
		return;
	}

	target_uvdc = omap_voltage_get_nom_volt(voltdm);
	if (!target_uvdc) {
		pr_err("%s: unable to find current voltage for vdd_%s\n",
			__func__, voltdm->name);
		return;
	}

	omap_voltage_scale_vdd(voltdm, target_uvdc);
}

/**
 * omap_voltage_get_volttable() - API to get the voltage table associated with a
 *				particular voltage domain.
 * @voltdm:	pointer to the VDD for which the voltage table is required
 * @volt_data:	the voltage table for the particular vdd which is to be
 *		populated by this API
 *
 * This API populates the voltage table associated with a VDD into the
 * passed parameter pointer. Returns the count of distinct voltages
 * supported by this vdd.
 *
 */
void omap_voltage_get_volttable(struct voltagedomain *voltdm,
		struct omap_volt_data **volt_data)
{
	struct omap_vdd_info *vdd;

	if (!voltdm || IS_ERR(voltdm)) {
		pr_warning("%s: VDD specified does not exist!\n", __func__);
		return;
	}

	vdd = voltdm->vdd;

	*volt_data = vdd->volt_data;
}

/**
 * omap_voltage_get_voltdata() - API to get the voltage table entry for a
 *				particular voltage
 * @voltdm:	pointer to the VDD whose voltage table has to be searched
 * @volt:	the voltage to be searched in the voltage table
 *
 * This API searches through the voltage table for the required voltage
 * domain and tries to find a matching entry for the passed voltage volt.
 * If a matching entry is found volt_data is populated with that entry.
 * This API searches only through the non-compensated voltages int the
 * voltage table.
 * Returns pointer to the voltage table entry corresponding to volt on
 * success. Returns -ENODATA if no voltage table exisits for the passed voltage
 * domain or if there is no matching entry.
 */
struct omap_volt_data *omap_voltage_get_voltdata(struct voltagedomain *voltdm,
		unsigned long volt)
{
	struct omap_vdd_info *vdd;
	int i;

	if (!voltdm || IS_ERR(voltdm)) {
		pr_warning("%s: VDD specified does not exist!\n", __func__);
		return ERR_PTR(-EINVAL);
	}

	vdd = voltdm->vdd;

	if (!vdd->volt_data) {
		pr_warning("%s: voltage table does not exist for vdd_%s\n",
			__func__, voltdm->name);
		return ERR_PTR(-ENODATA);
	}

	for (i = 0; vdd->volt_data[i].volt_nominal != 0; i++) {
		if (vdd->volt_data[i].volt_nominal == volt)
			return &vdd->volt_data[i];
	}

	pr_notice("%s: Unable to match the current voltage with the voltage"
		"table for vdd_%s\n", __func__, voltdm->name);

	return ERR_PTR(-ENODATA);
}

/**
 * omap_voltage_register_pmic() - API to register PMIC specific data
 * @voltdm:	pointer to the VDD for which the PMIC specific data is
 *		to be registered
 * @pmic_info:	the structure containing pmic info
 *
 * This API is to be called by the SOC/PMIC file to specify the
 * pmic specific info as present in omap_volt_pmic_info structure.
 */
int omap_voltage_register_pmic(struct voltagedomain *voltdm,
		struct omap_volt_pmic_info *pmic_info)
{
	struct omap_vdd_info *vdd;

	if (!voltdm || IS_ERR(voltdm)) {
		pr_warning("%s: VDD specified does not exist!\n", __func__);
		return -EINVAL;
	}

	vdd = voltdm->vdd;

	vdd->pmic_info = pmic_info;

	return 0;
}

/**
 * omap_voltage_get_dbgdir() - API to get pointer to the debugfs directory
 *				corresponding to a voltage domain.
 *
 * @voltdm:	pointer to the VDD whose debug directory is required.
 *
 * This API returns pointer to the debugfs directory corresponding
 * to the voltage domain. Should be used by drivers requiring to
 * add any debug entry for a particular voltage domain. Returns NULL
 * in case of error.
 */
struct dentry *omap_voltage_get_dbgdir(struct voltagedomain *voltdm)
{
	struct omap_vdd_info *vdd;

	if (!voltdm || IS_ERR(voltdm)) {
		pr_warning("%s: VDD specified does not exist!\n", __func__);
		return NULL;
	}

	vdd = voltdm->vdd;

	return vdd->debug_dir;
}

/**
 * omap_change_voltscale_method() - API to change the voltage scaling method.
 * @voltdm:	pointer to the VDD whose voltage scaling method
 *		has to be changed.
 * @voltscale_method:	the method to be used for voltage scaling.
 *
 * This API can be used by the board files to change the method of voltage
 * scaling between vpforceupdate and vcbypass. The parameter values are
 * defined in voltage.h
 */
void omap_change_voltscale_method(struct voltagedomain *voltdm,
		int voltscale_method)
{
	struct omap_vdd_info *vdd;

	if (!voltdm || IS_ERR(voltdm)) {
		pr_warning("%s: VDD specified does not exist!\n", __func__);
		return;
	}

	vdd = voltdm->vdd;

	switch (voltscale_method) {
	case VOLTSCALE_VPFORCEUPDATE:
		vdd->volt_scale = vp_forceupdate_scale_voltage;
		return;
	case VOLTSCALE_VCBYPASS:
		vdd->volt_scale = omap_vc_bypass_scale_voltage;
		return;
	default:
		pr_warning("%s: Trying to change the method of voltage scaling"
			"to an unsupported one!\n", __func__);
	}
}

/**
 * omap_voltage_late_init() - Init the various voltage parameters
 *
 * This API is to be called in the later stages of the
 * system boot to init the voltage controller and
 * voltage processors.
 */
int __init omap_voltage_late_init(void)
{
	struct voltagedomain *voltdm;

	if (list_empty(&voltdm_list)) {
		pr_err("%s: Voltage driver support not added\n",
			__func__);
		return -EINVAL;
	}

	voltage_dir = debugfs_create_dir("voltage", NULL);
	if (IS_ERR(voltage_dir))
		pr_err("%s: Unable to create voltage debugfs main dir\n",
			__func__);
	list_for_each_entry(voltdm, &voltdm_list, node) {
		if (!voltdm->scalable)
			continue;

		if (voltdm->vdd) {
			if (omap_vdd_data_configure(voltdm))
				continue;
			omap_vc_init_channel(voltdm);
			vp_init(voltdm);
			vdd_debugfs_init(voltdm);
		}
	}

	return 0;
}

static struct voltagedomain *_voltdm_lookup(const char *name)
{
	struct voltagedomain *voltdm, *temp_voltdm;

	voltdm = NULL;

	list_for_each_entry(temp_voltdm, &voltdm_list, node) {
		if (!strcmp(name, temp_voltdm->name)) {
			voltdm = temp_voltdm;
			break;
		}
	}

	return voltdm;
}

/**
 * voltdm_add_pwrdm - add a powerdomain to a voltagedomain
 * @voltdm: struct voltagedomain * to add the powerdomain to
 * @pwrdm: struct powerdomain * to associate with a voltagedomain
 *
 * Associate the powerdomain @pwrdm with a voltagedomain @voltdm.  This
 * enables the use of voltdm_for_each_pwrdm().  Returns -EINVAL if
 * presented with invalid pointers; -ENOMEM if memory could not be allocated;
 * or 0 upon success.
 */
int voltdm_add_pwrdm(struct voltagedomain *voltdm, struct powerdomain *pwrdm)
{
	if (!voltdm || !pwrdm)
		return -EINVAL;

	pr_debug("voltagedomain: associating powerdomain %s with voltagedomain "
		 "%s\n", pwrdm->name, voltdm->name);

	list_add(&pwrdm->voltdm_node, &voltdm->pwrdm_list);

	return 0;
}

/**
 * voltdm_for_each_pwrdm - call function for each pwrdm in a voltdm
 * @voltdm: struct voltagedomain * to iterate over
 * @fn: callback function *
 *
 * Call the supplied function @fn for each powerdomain in the
 * voltagedomain @voltdm.  Returns -EINVAL if presented with invalid
 * pointers; or passes along the last return value of the callback
 * function, which should be 0 for success or anything else to
 * indicate failure.
 */
int voltdm_for_each_pwrdm(struct voltagedomain *voltdm,
			  int (*fn)(struct voltagedomain *voltdm,
				    struct powerdomain *pwrdm))
{
	struct powerdomain *pwrdm;
	int ret = 0;

	if (!fn)
		return -EINVAL;

	list_for_each_entry(pwrdm, &voltdm->pwrdm_list, voltdm_node)
		ret = (*fn)(voltdm, pwrdm);

	return ret;
}

/**
 * voltdm_for_each - call function on each registered voltagedomain
 * @fn: callback function *
 *
 * Call the supplied function @fn for each registered voltagedomain.
 * The callback function @fn can return anything but 0 to bail out
 * early from the iterator.  Returns the last return value of the
 * callback function, which should be 0 for success or anything else
 * to indicate failure; or -EINVAL if the function pointer is null.
 */
int voltdm_for_each(int (*fn)(struct voltagedomain *voltdm, void *user),
		    void *user)
{
	struct voltagedomain *temp_voltdm;
	int ret = 0;

	if (!fn)
		return -EINVAL;

	list_for_each_entry(temp_voltdm, &voltdm_list, node) {
		ret = (*fn)(temp_voltdm, user);
		if (ret)
			break;
	}

	return ret;
}

static int _voltdm_register(struct voltagedomain *voltdm)
{
	if (!voltdm || !voltdm->name)
		return -EINVAL;

	INIT_LIST_HEAD(&voltdm->pwrdm_list);
	list_add(&voltdm->node, &voltdm_list);

	pr_debug("voltagedomain: registered %s\n", voltdm->name);

	return 0;
}

/**
 * voltdm_lookup - look up a voltagedomain by name, return a pointer
 * @name: name of voltagedomain
 *
 * Find a registered voltagedomain by its name @name.  Returns a pointer
 * to the struct voltagedomain if found, or NULL otherwise.
 */
struct voltagedomain *voltdm_lookup(const char *name)
{
	struct voltagedomain *voltdm ;

	if (!name)
		return NULL;

	voltdm = _voltdm_lookup(name);

	return voltdm;
}

/**
 * voltdm_init - set up the voltagedomain layer
 * @voltdm_list: array of struct voltagedomain pointers to register
 *
 * Loop through the array of voltagedomains @voltdm_list, registering all
 * that are available on the current CPU. If voltdm_list is supplied
 * and not null, all of the referenced voltagedomains will be
 * registered.  No return value.
 */
void voltdm_init(struct voltagedomain **voltdms)
{
	struct voltagedomain **v;

	if (voltdms) {
		for (v = voltdms; *v; v++)
			_voltdm_register(*v);
	}
}