mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race

[linux/fpc-iii.git] / arch / arm / mach-omap2 / vc.c

/*
 * OMAP Voltage Controller (VC) interface
 *
 * Copyright (C) 2011 Texas Instruments, Inc.
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/bug.h>
#include <linux/io.h>

#include <asm/div64.h>

#include "iomap.h"
#include "soc.h"
#include "voltage.h"
#include "vc.h"
#include "prm-regbits-34xx.h"
#include "prm-regbits-44xx.h"
#include "prm44xx.h"
#include "pm.h"
#include "scrm44xx.h"
#include "control.h"

/**
 * struct omap_vc_channel_cfg - describe the cfg_channel bitfield
 * @sa: bit for slave address
 * @rav: bit for voltage configuration register
 * @rac: bit for command configuration register
 * @racen: enable bit for RAC
 * @cmd: bit for command value set selection
 *
 * Channel configuration bits, common for OMAP3+
 * OMAP3 register: PRM_VC_CH_CONF
 * OMAP4 register: PRM_VC_CFG_CHANNEL
 * OMAP5 register: PRM_VC_SMPS_<voltdm>_CONFIG
 */
struct omap_vc_channel_cfg {
        u8 sa;
        u8 rav;
        u8 rac;
        u8 racen;
        u8 cmd;
};

static struct omap_vc_channel_cfg vc_default_channel_cfg = {
        .sa    = BIT(0),
        .rav   = BIT(1),
        .rac   = BIT(2),
        .racen = BIT(3),
        .cmd   = BIT(4),
};

/*
 * On OMAP3+, all VC channels have the above default bitfield
 * configuration, except the OMAP4 MPU channel.  This appears
 * to be a freak accident as every other VC channel has the
 * default configuration, thus creating a mutant channel config.
 */
static struct omap_vc_channel_cfg vc_mutant_channel_cfg = {
        .sa    = BIT(0),
        .rav   = BIT(2),
        .rac   = BIT(3),
        .racen = BIT(4),
        .cmd   = BIT(1),
};

static struct omap_vc_channel_cfg *vc_cfg_bits;

/* Default I2C trace length on pcb, 6.3cm. Used for capacitance calculations. */
static u32 sr_i2c_pcb_length = 63;
#define CFG_CHANNEL_MASK 0x1f

/**
 * omap_vc_config_channel - configure VC channel to PMIC mappings
 * @voltdm: pointer to voltagdomain defining the desired VC channel
 *
 * Configures the VC channel to PMIC mappings for the following
 * PMIC settings
 * - i2c slave address (SA)
 * - voltage configuration address (RAV)
 * - command configuration address (RAC) and enable bit (RACEN)
 * - command values for ON, ONLP, RET and OFF (CMD)
 *
 * This function currently only allows flexible configuration of the
 * non-default channel.  Starting with OMAP4, there are more than 2
 * channels, with one defined as the default (on OMAP4, it's MPU.)
 * Only the non-default channel can be configured.
 */
static int omap_vc_config_channel(struct voltagedomain *voltdm)
{
        struct omap_vc_channel *vc = voltdm->vc;

        /*
         * For default channel, the only configurable bit is RACEN.
         * All others must stay at zero (see function comment above.)
         */
        if (vc->flags & OMAP_VC_CHANNEL_DEFAULT)
                vc->cfg_channel &= vc_cfg_bits->racen;

        voltdm->rmw(CFG_CHANNEL_MASK << vc->cfg_channel_sa_shift,
                    vc->cfg_channel << vc->cfg_channel_sa_shift,
                    vc->cfg_channel_reg);

        return 0;
}

/* Voltage scale and accessory APIs */
int omap_vc_pre_scale(struct voltagedomain *voltdm,
                      unsigned long target_volt,
                      u8 *target_vsel, u8 *current_vsel)
{
        struct omap_vc_channel *vc = voltdm->vc;
        u32 vc_cmdval;

        /* Check if sufficient pmic info is available for this vdd */
        if (!voltdm->pmic) {
                pr_err("%s: Insufficient pmic info to scale the vdd_%s\n",
                        __func__, voltdm->name);
                return -EINVAL;
        }

        if (!voltdm->pmic->uv_to_vsel) {
                pr_err("%s: PMIC function to convert voltage in uV to vsel not registered. Hence unable to scale voltage for vdd_%s\n",
                       __func__, voltdm->name);
                return -ENODATA;
        }

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

        *target_vsel = voltdm->pmic->uv_to_vsel(target_volt);
        *current_vsel = voltdm->pmic->uv_to_vsel(voltdm->nominal_volt);

        /* Setting the ON voltage to the new target voltage */
        vc_cmdval = voltdm->read(vc->cmdval_reg);
        vc_cmdval &= ~vc->common->cmd_on_mask;
        vc_cmdval |= (*target_vsel << vc->common->cmd_on_shift);
        voltdm->write(vc_cmdval, vc->cmdval_reg);

        voltdm->vc_param->on = target_volt;

        omap_vp_update_errorgain(voltdm, target_volt);

        return 0;
}

void omap_vc_post_scale(struct voltagedomain *voltdm,
                        unsigned long target_volt,
                        u8 target_vsel, u8 current_vsel)
{
        u32 smps_steps = 0, smps_delay = 0;

        smps_steps = abs(target_vsel - current_vsel);
        /* SMPS slew rate / step size. 2us added as buffer. */
        smps_delay = ((smps_steps * voltdm->pmic->step_size) /
                        voltdm->pmic->slew_rate) + 2;
        udelay(smps_delay);
}

/* vc_bypass_scale - VC bypass method of voltage scaling */
int omap_vc_bypass_scale(struct voltagedomain *voltdm,
                         unsigned long target_volt)
{
        struct omap_vc_channel *vc = voltdm->vc;
        u32 loop_cnt = 0, retries_cnt = 0;
        u32 vc_valid, vc_bypass_val_reg, vc_bypass_value;
        u8 target_vsel, current_vsel;
        int ret;

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

        vc_valid = vc->common->valid;
        vc_bypass_val_reg = vc->common->bypass_val_reg;
        vc_bypass_value = (target_vsel << vc->common->data_shift) |
                (vc->volt_reg_addr << vc->common->regaddr_shift) |
                (vc->i2c_slave_addr << vc->common->slaveaddr_shift);

        voltdm->write(vc_bypass_value, vc_bypass_val_reg);
        voltdm->write(vc_bypass_value | vc_valid, vc_bypass_val_reg);

        vc_bypass_value = voltdm->read(vc_bypass_val_reg);
        /*
         * Loop till the bypass command is acknowledged from the SMPS.
         * NOTE: This is legacy code. The loop count and retry count needs
         * to be revisited.
         */
        while (!(vc_bypass_value & vc_valid)) {
                loop_cnt++;

                if (retries_cnt > 10) {
                        pr_warn("%s: Retry count exceeded\n", __func__);
                        return -ETIMEDOUT;
                }

                if (loop_cnt > 50) {
                        retries_cnt++;
                        loop_cnt = 0;
                        udelay(10);
                }
                vc_bypass_value = voltdm->read(vc_bypass_val_reg);
        }

        omap_vc_post_scale(voltdm, target_volt, target_vsel, current_vsel);
        return 0;
}

/* Convert microsecond value to number of 32kHz clock cycles */
static inline u32 omap_usec_to_32k(u32 usec)
{
        return DIV_ROUND_UP_ULL(32768ULL * (u64)usec, 1000000ULL);
}

struct omap3_vc_timings {
        u32 voltsetup1;
        u32 voltsetup2;
};

struct omap3_vc {
        struct voltagedomain *vd;
        u32 voltctrl;
        u32 voltsetup1;
        u32 voltsetup2;
        struct omap3_vc_timings timings[2];
};
static struct omap3_vc vc;

void omap3_vc_set_pmic_signaling(int core_next_state)
{
        struct voltagedomain *vd = vc.vd;
        struct omap3_vc_timings *c = vc.timings;
        u32 voltctrl, voltsetup1, voltsetup2;

        voltctrl = vc.voltctrl;
        voltsetup1 = vc.voltsetup1;
        voltsetup2 = vc.voltsetup2;

        switch (core_next_state) {
        case PWRDM_POWER_OFF:
                voltctrl &= ~(OMAP3430_PRM_VOLTCTRL_AUTO_RET |
                              OMAP3430_PRM_VOLTCTRL_AUTO_SLEEP);
                voltctrl |= OMAP3430_PRM_VOLTCTRL_AUTO_OFF;
                if (voltctrl & OMAP3430_PRM_VOLTCTRL_SEL_OFF)
                        voltsetup2 = c->voltsetup2;
                else
                        voltsetup1 = c->voltsetup1;
                break;
        case PWRDM_POWER_RET:
        default:
                c++;
                voltctrl &= ~(OMAP3430_PRM_VOLTCTRL_AUTO_OFF |
                              OMAP3430_PRM_VOLTCTRL_AUTO_SLEEP);
                voltctrl |= OMAP3430_PRM_VOLTCTRL_AUTO_RET;
                voltsetup1 = c->voltsetup1;
                break;
        }

        if (voltctrl != vc.voltctrl) {
                vd->write(voltctrl, OMAP3_PRM_VOLTCTRL_OFFSET);
                vc.voltctrl = voltctrl;
        }
        if (voltsetup1 != vc.voltsetup1) {
                vd->write(c->voltsetup1,
                          OMAP3_PRM_VOLTSETUP1_OFFSET);
                vc.voltsetup1 = voltsetup1;
        }
        if (voltsetup2 != vc.voltsetup2) {
                vd->write(c->voltsetup2,
                          OMAP3_PRM_VOLTSETUP2_OFFSET);
                vc.voltsetup2 = voltsetup2;
        }
}

/*
 * Configure signal polarity for sys_clkreq and sys_off_mode pins
 * as the default values are wrong and can cause the system to hang
 * if any twl4030 scripts are loaded.
 */
static void __init omap3_vc_init_pmic_signaling(struct voltagedomain *voltdm)
{
        u32 val;

        if (vc.vd)
                return;

        vc.vd = voltdm;

        val = voltdm->read(OMAP3_PRM_POLCTRL_OFFSET);
        if (!(val & OMAP3430_PRM_POLCTRL_CLKREQ_POL) ||
            (val & OMAP3430_PRM_POLCTRL_OFFMODE_POL)) {
                val |= OMAP3430_PRM_POLCTRL_CLKREQ_POL;
                val &= ~OMAP3430_PRM_POLCTRL_OFFMODE_POL;
                pr_debug("PM: fixing sys_clkreq and sys_off_mode polarity to 0x%x\n",
                         val);
                voltdm->write(val, OMAP3_PRM_POLCTRL_OFFSET);
        }

        /*
         * By default let's use I2C4 signaling for retention idle
         * and sys_off_mode pin signaling for off idle. This way we
         * have sys_clk_req pin go down for retention and both
         * sys_clk_req and sys_off_mode pins will go down for off
         * idle. And we can also scale voltages to zero for off-idle.
         * Note that no actual voltage scaling during off-idle will
         * happen unless the board specific twl4030 PMIC scripts are
         * loaded. See also omap_vc_i2c_init for comments regarding
         * erratum i531.
         */
        val = voltdm->read(OMAP3_PRM_VOLTCTRL_OFFSET);
        if (!(val & OMAP3430_PRM_VOLTCTRL_SEL_OFF)) {
                val |= OMAP3430_PRM_VOLTCTRL_SEL_OFF;
                pr_debug("PM: setting voltctrl sys_off_mode signaling to 0x%x\n",
                         val);
                voltdm->write(val, OMAP3_PRM_VOLTCTRL_OFFSET);
        }
        vc.voltctrl = val;

        omap3_vc_set_pmic_signaling(PWRDM_POWER_ON);
}

static void omap3_init_voltsetup1(struct voltagedomain *voltdm,
                                  struct omap3_vc_timings *c, u32 idle)
{
        unsigned long val;

        val = (voltdm->vc_param->on - idle) / voltdm->pmic->slew_rate;
        val *= voltdm->sys_clk.rate / 8 / 1000000 + 1;
        val <<= __ffs(voltdm->vfsm->voltsetup_mask);
        c->voltsetup1 &= ~voltdm->vfsm->voltsetup_mask;
        c->voltsetup1 |= val;
}

/**
 * omap3_set_i2c_timings - sets i2c sleep timings for a channel
 * @voltdm: channel to configure
 * @off_mode: select whether retention or off mode values used
 *
 * Calculates and sets up voltage controller to use I2C based
 * voltage scaling for sleep modes. This can be used for either off mode
 * or retention. Off mode has additionally an option to use sys_off_mode
 * pad, which uses a global signal to program the whole power IC to
 * off-mode.
 *
 * Note that pmic is not controlling the voltage scaling during
 * retention signaled over I2C4, so we can keep voltsetup2 as 0.
 * And the oscillator is not shut off over I2C4, so no need to
 * set clksetup.
 */
static void omap3_set_i2c_timings(struct voltagedomain *voltdm)
{
        struct omap3_vc_timings *c = vc.timings;

        /* Configure PRWDM_POWER_OFF over I2C4 */
        omap3_init_voltsetup1(voltdm, c, voltdm->vc_param->off);
        c++;
        /* Configure PRWDM_POWER_RET over I2C4 */
        omap3_init_voltsetup1(voltdm, c, voltdm->vc_param->ret);
}

/**
 * omap3_set_off_timings - sets off-mode timings for a channel
 * @voltdm: channel to configure
 *
 * Calculates and sets up off-mode timings for a channel. Off-mode
 * can use either I2C based voltage scaling, or alternatively
 * sys_off_mode pad can be used to send a global command to power IC.n,
 * sys_off_mode has the additional benefit that voltages can be
 * scaled to zero volt level with TWL4030 / TWL5030, I2C can only
 * scale to 600mV.
 *
 * Note that omap is not controlling the voltage scaling during
 * off idle signaled by sys_off_mode, so we can keep voltsetup1
 * as 0.
 */
static void omap3_set_off_timings(struct voltagedomain *voltdm)
{
        struct omap3_vc_timings *c = vc.timings;
        u32 tstart, tshut, clksetup, voltoffset;

        if (c->voltsetup2)
                return;

        omap_pm_get_oscillator(&tstart, &tshut);
        if (tstart == ULONG_MAX) {
                pr_debug("PM: oscillator start-up time not initialized, using 10ms\n");
                clksetup = omap_usec_to_32k(10000);
        } else {
                clksetup = omap_usec_to_32k(tstart);
        }

        /*
         * For twl4030 errata 27, we need to allow minimum ~488.32 us wait to
         * switch from HFCLKIN to internal oscillator. That means timings
         * have voltoffset fixed to 0xa in rounded up 32 KiHz cycles. And
         * that means we can calculate the value based on the oscillator
         * start-up time since voltoffset2 = clksetup - voltoffset.
         */
        voltoffset = omap_usec_to_32k(488);
        c->voltsetup2 = clksetup - voltoffset;
        voltdm->write(clksetup, OMAP3_PRM_CLKSETUP_OFFSET);
        voltdm->write(voltoffset, OMAP3_PRM_VOLTOFFSET_OFFSET);
}

static void __init omap3_vc_init_channel(struct voltagedomain *voltdm)
{
        omap3_vc_init_pmic_signaling(voltdm);
        omap3_set_off_timings(voltdm);
        omap3_set_i2c_timings(voltdm);
}

/**
 * omap4_calc_volt_ramp - calculates voltage ramping delays on omap4
 * @voltdm: channel to calculate values for
 * @voltage_diff: voltage difference in microvolts
 *
 * Calculates voltage ramp prescaler + counter values for a voltage
 * difference on omap4. Returns a field value suitable for writing to
 * VOLTSETUP register for a channel in following format:
 * bits[8:9] prescaler ... bits[0:5] counter. See OMAP4 TRM for reference.
 */
static u32 omap4_calc_volt_ramp(struct voltagedomain *voltdm, u32 voltage_diff)
{
        u32 prescaler;
        u32 cycles;
        u32 time;

        time = voltage_diff / voltdm->pmic->slew_rate;

        cycles = voltdm->sys_clk.rate / 1000 * time / 1000;

        cycles /= 64;
        prescaler = 0;

        /* shift to next prescaler until no overflow */

        /* scale for div 256 = 64 * 4 */
        if (cycles > 63) {
                cycles /= 4;
                prescaler++;
        }

        /* scale for div 512 = 256 * 2 */
        if (cycles > 63) {
                cycles /= 2;
                prescaler++;
        }

        /* scale for div 2048 = 512 * 4 */
        if (cycles > 63) {
                cycles /= 4;
                prescaler++;
        }

        /* check for overflow => invalid ramp time */
        if (cycles > 63) {
                pr_warn("%s: invalid setuptime for vdd_%s\n", __func__,
                        voltdm->name);
                return 0;
        }

        cycles++;

        return (prescaler << OMAP4430_RAMP_UP_PRESCAL_SHIFT) |
                (cycles << OMAP4430_RAMP_UP_COUNT_SHIFT);
}

/**
 * omap4_usec_to_val_scrm - convert microsecond value to SCRM module bitfield
 * @usec: microseconds
 * @shift: number of bits to shift left
 * @mask: bitfield mask
 *
 * Converts microsecond value to OMAP4 SCRM bitfield. Bitfield is
 * shifted to requested position, and checked agains the mask value.
 * If larger, forced to the max value of the field (i.e. the mask itself.)
 * Returns the SCRM bitfield value.
 */
static u32 omap4_usec_to_val_scrm(u32 usec, int shift, u32 mask)
{
        u32 val;

        val = omap_usec_to_32k(usec) << shift;

        /* Check for overflow, if yes, force to max value */
        if (val > mask)
                val = mask;

        return val;
}

/**
 * omap4_set_timings - set voltage ramp timings for a channel
 * @voltdm: channel to configure
 * @off_mode: whether off-mode values are used
 *
 * Calculates and sets the voltage ramp up / down values for a channel.
 */
static void omap4_set_timings(struct voltagedomain *voltdm, bool off_mode)
{
        u32 val;
        u32 ramp;
        int offset;
        u32 tstart, tshut;

        if (off_mode) {
                ramp = omap4_calc_volt_ramp(voltdm,
                        voltdm->vc_param->on - voltdm->vc_param->off);
                offset = voltdm->vfsm->voltsetup_off_reg;
        } else {
                ramp = omap4_calc_volt_ramp(voltdm,
                        voltdm->vc_param->on - voltdm->vc_param->ret);
                offset = voltdm->vfsm->voltsetup_reg;
        }

        if (!ramp)
                return;

        val = voltdm->read(offset);

        val |= ramp << OMAP4430_RAMP_DOWN_COUNT_SHIFT;

        val |= ramp << OMAP4430_RAMP_UP_COUNT_SHIFT;

        voltdm->write(val, offset);

        omap_pm_get_oscillator(&tstart, &tshut);

        val = omap4_usec_to_val_scrm(tstart, OMAP4_SETUPTIME_SHIFT,
                OMAP4_SETUPTIME_MASK);
        val |= omap4_usec_to_val_scrm(tshut, OMAP4_DOWNTIME_SHIFT,
                OMAP4_DOWNTIME_MASK);

        writel_relaxed(val, OMAP4_SCRM_CLKSETUPTIME);
}

/* OMAP4 specific voltage init functions */
static void __init omap4_vc_init_channel(struct voltagedomain *voltdm)
{
        omap4_set_timings(voltdm, true);
        omap4_set_timings(voltdm, false);
}

struct i2c_init_data {
        u8 loadbits;
        u8 load;
        u8 hsscll_38_4;
        u8 hsscll_26;
        u8 hsscll_19_2;
        u8 hsscll_16_8;
        u8 hsscll_12;
};

static const struct i2c_init_data omap4_i2c_timing_data[] __initconst = {
        {
                .load = 50,
                .loadbits = 0x3,
                .hsscll_38_4 = 13,
                .hsscll_26 = 11,
                .hsscll_19_2 = 9,
                .hsscll_16_8 = 9,
                .hsscll_12 = 8,
        },
        {
                .load = 25,
                .loadbits = 0x2,
                .hsscll_38_4 = 13,
                .hsscll_26 = 11,
                .hsscll_19_2 = 9,
                .hsscll_16_8 = 9,
                .hsscll_12 = 8,
        },
        {
                .load = 12,
                .loadbits = 0x1,
                .hsscll_38_4 = 11,
                .hsscll_26 = 10,
                .hsscll_19_2 = 9,
                .hsscll_16_8 = 9,
                .hsscll_12 = 8,
        },
        {
                .load = 0,
                .loadbits = 0x0,
                .hsscll_38_4 = 12,
                .hsscll_26 = 10,
                .hsscll_19_2 = 9,
                .hsscll_16_8 = 8,
                .hsscll_12 = 8,
        },
};

/**
 * omap4_vc_i2c_timing_init - sets up board I2C timing parameters
 * @voltdm: voltagedomain pointer to get data from
 *
 * Use PMIC + board supplied settings for calculating the total I2C
 * channel capacitance and set the timing parameters based on this.
 * Pre-calculated values are provided in data tables, as it is not
 * too straightforward to calculate these runtime.
 */
static void __init omap4_vc_i2c_timing_init(struct voltagedomain *voltdm)
{
        u32 capacitance;
        u32 val;
        u16 hsscll;
        const struct i2c_init_data *i2c_data;

        if (!voltdm->pmic->i2c_high_speed) {
                pr_warn("%s: only high speed supported!\n", __func__);
                return;
        }

        /* PCB trace capacitance, 0.125pF / mm => mm / 8 */
        capacitance = DIV_ROUND_UP(sr_i2c_pcb_length, 8);

        /* OMAP pad capacitance */
        capacitance += 4;

        /* PMIC pad capacitance */
        capacitance += voltdm->pmic->i2c_pad_load;

        /* Search for capacitance match in the table */
        i2c_data = omap4_i2c_timing_data;

        while (i2c_data->load > capacitance)
                i2c_data++;

        /* Select proper values based on sysclk frequency */
        switch (voltdm->sys_clk.rate) {
        case 38400000:
                hsscll = i2c_data->hsscll_38_4;
                break;
        case 26000000:
                hsscll = i2c_data->hsscll_26;
                break;
        case 19200000:
                hsscll = i2c_data->hsscll_19_2;
                break;
        case 16800000:
                hsscll = i2c_data->hsscll_16_8;
                break;
        case 12000000:
                hsscll = i2c_data->hsscll_12;
                break;
        default:
                pr_warn("%s: unsupported sysclk rate: %d!\n", __func__,
                        voltdm->sys_clk.rate);
                return;
        }

        /* Loadbits define pull setup for the I2C channels */
        val = i2c_data->loadbits << 25 | i2c_data->loadbits << 29;

        /* Write to SYSCTRL_PADCONF_WKUP_CTRL_I2C_2 to setup I2C pull */
        writel_relaxed(val, OMAP2_L4_IO_ADDRESS(OMAP4_CTRL_MODULE_PAD_WKUP +
                                OMAP4_CTRL_MODULE_PAD_WKUP_CONTROL_I2C_2));

        /* HSSCLH can always be zero */
        val = hsscll << OMAP4430_HSSCLL_SHIFT;
        val |= (0x28 << OMAP4430_SCLL_SHIFT | 0x2c << OMAP4430_SCLH_SHIFT);

        /* Write setup times to I2C config register */
        voltdm->write(val, OMAP4_PRM_VC_CFG_I2C_CLK_OFFSET);
}



/**
 * omap_vc_i2c_init - initialize I2C interface to PMIC
 * @voltdm: voltage domain containing VC data
 *
 * Use PMIC supplied settings for I2C high-speed mode and
 * master code (if set) and program the VC I2C configuration
 * register.
 *
 * The VC I2C configuration is common to all VC channels,
 * so this function only configures I2C for the first VC
 * channel registers.  All other VC channels will use the
 * same configuration.
 */
static void __init omap_vc_i2c_init(struct voltagedomain *voltdm)
{
        struct omap_vc_channel *vc = voltdm->vc;
        static bool initialized;
        static bool i2c_high_speed;
        u8 mcode;

        if (initialized) {
                if (voltdm->pmic->i2c_high_speed != i2c_high_speed)
                        pr_warn("%s: I2C config for vdd_%s does not match other channels (%u).\n",
                                __func__, voltdm->name, i2c_high_speed);
                return;
        }

        /*
         * Note that for omap3 OMAP3430_SREN_MASK clears SREN to work around
         * erratum i531 "Extra Power Consumed When Repeated Start Operation
         * Mode Is Enabled on I2C Interface Dedicated for Smart Reflex (I2C4)".
         * Otherwise I2C4 eventually leads into about 23mW extra power being
         * consumed even during off idle using VMODE.
         */
        i2c_high_speed = voltdm->pmic->i2c_high_speed;
        if (i2c_high_speed)
                voltdm->rmw(vc->common->i2c_cfg_clear_mask,
                            vc->common->i2c_cfg_hsen_mask,
                            vc->common->i2c_cfg_reg);

        mcode = voltdm->pmic->i2c_mcode;
        if (mcode)
                voltdm->rmw(vc->common->i2c_mcode_mask,
                            mcode << __ffs(vc->common->i2c_mcode_mask),
                            vc->common->i2c_cfg_reg);

        if (cpu_is_omap44xx())
                omap4_vc_i2c_timing_init(voltdm);

        initialized = true;
}

/**
 * omap_vc_calc_vsel - calculate vsel value for a channel
 * @voltdm: channel to calculate value for
 * @uvolt: microvolt value to convert to vsel
 *
 * Converts a microvolt value to vsel value for the used PMIC.
 * This checks whether the microvolt value is out of bounds, and
 * adjusts the value accordingly. If unsupported value detected,
 * warning is thrown.
 */
static u8 omap_vc_calc_vsel(struct voltagedomain *voltdm, u32 uvolt)
{
        if (voltdm->pmic->vddmin > uvolt)
                uvolt = voltdm->pmic->vddmin;
        if (voltdm->pmic->vddmax < uvolt) {
                WARN(1, "%s: voltage not supported by pmic: %u vs max %u\n",
                        __func__, uvolt, voltdm->pmic->vddmax);
                /* Lets try maximum value anyway */
                uvolt = voltdm->pmic->vddmax;
        }

        return voltdm->pmic->uv_to_vsel(uvolt);
}

#ifdef CONFIG_PM
/**
 * omap_pm_setup_sr_i2c_pcb_length - set length of SR I2C traces on PCB
 * @mm: length of the PCB trace in millimetres
 *
 * Sets the PCB trace length for the I2C channel. By default uses 63mm.
 * This is needed for properly calculating the capacitance value for
 * the PCB trace, and for setting the SR I2C channel timing parameters.
 */
void __init omap_pm_setup_sr_i2c_pcb_length(u32 mm)
{
        sr_i2c_pcb_length = mm;
}
#endif

void __init omap_vc_init_channel(struct voltagedomain *voltdm)
{
        struct omap_vc_channel *vc = voltdm->vc;
        u8 on_vsel, onlp_vsel, ret_vsel, off_vsel;
        u32 val;

        if (!voltdm->pmic || !voltdm->pmic->uv_to_vsel) {
                pr_err("%s: No PMIC info for vdd_%s\n", __func__, voltdm->name);
                return;
        }

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

        vc->cfg_channel = 0;
        if (vc->flags & OMAP_VC_CHANNEL_CFG_MUTANT)
                vc_cfg_bits = &vc_mutant_channel_cfg;
        else
                vc_cfg_bits = &vc_default_channel_cfg;

        /* get PMIC/board specific settings */
        vc->i2c_slave_addr = voltdm->pmic->i2c_slave_addr;
        vc->volt_reg_addr = voltdm->pmic->volt_reg_addr;
        vc->cmd_reg_addr = voltdm->pmic->cmd_reg_addr;

        /* Configure the i2c slave address for this VC */
        voltdm->rmw(vc->smps_sa_mask,
                    vc->i2c_slave_addr << __ffs(vc->smps_sa_mask),
                    vc->smps_sa_reg);
        vc->cfg_channel |= vc_cfg_bits->sa;

        /*
         * Configure the PMIC register addresses.
         */
        voltdm->rmw(vc->smps_volra_mask,
                    vc->volt_reg_addr << __ffs(vc->smps_volra_mask),
                    vc->smps_volra_reg);
        vc->cfg_channel |= vc_cfg_bits->rav;

        if (vc->cmd_reg_addr) {
                voltdm->rmw(vc->smps_cmdra_mask,
                            vc->cmd_reg_addr << __ffs(vc->smps_cmdra_mask),
                            vc->smps_cmdra_reg);
                vc->cfg_channel |= vc_cfg_bits->rac;
        }

        if (vc->cmd_reg_addr == vc->volt_reg_addr)
                vc->cfg_channel |= vc_cfg_bits->racen;

        /* Set up the on, inactive, retention and off voltage */
        on_vsel = omap_vc_calc_vsel(voltdm, voltdm->vc_param->on);
        onlp_vsel = omap_vc_calc_vsel(voltdm, voltdm->vc_param->onlp);
        ret_vsel = omap_vc_calc_vsel(voltdm, voltdm->vc_param->ret);
        off_vsel = omap_vc_calc_vsel(voltdm, voltdm->vc_param->off);

        val = ((on_vsel << vc->common->cmd_on_shift) |
               (onlp_vsel << vc->common->cmd_onlp_shift) |
               (ret_vsel << vc->common->cmd_ret_shift) |
               (off_vsel << vc->common->cmd_off_shift));
        voltdm->write(val, vc->cmdval_reg);
        vc->cfg_channel |= vc_cfg_bits->cmd;

        /* Channel configuration */
        omap_vc_config_channel(voltdm);

        omap_vc_i2c_init(voltdm);

        if (cpu_is_omap34xx())
                omap3_vc_init_channel(voltdm);
        else if (cpu_is_omap44xx())
                omap4_vc_init_channel(voltdm);
}