OMAP clock: support "dry run" rate and parent changes

[linux-2.6-omap-h63xx.git] / arch / arm / mach-omap2 / clock.c

/*
 *  linux/arch/arm/mach-omap2/clock.c
 *
 *  Copyright (C) 2005-2008 Texas Instruments, Inc.
 *  Copyright (C) 2004-2008 Nokia Corporation
 *
 *  Contacts:
 *  Richard Woodruff <r-woodruff2@ti.com>
 *  Paul Walmsley
 *
 * 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.
 */
#undef DEBUG

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/list.h>
#include <linux/errno.h>
#include <linux/delay.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/bitops.h>

#include <mach/clock.h>
#include <mach/clockdomain.h>
#include <mach/sram.h>
#include <mach/cpu.h>
#include <mach/prcm.h>
#include <mach/control.h>
#include <asm/div64.h>

#include <mach/sdrc.h>
#include "sdrc.h"
#include "clock.h"
#include "prm.h"
#include "prm-regbits-24xx.h"
#include "cm.h"
#include "cm-regbits-24xx.h"
#include "cm-regbits-34xx.h"

#define MAX_CLOCK_ENABLE_WAIT           100000

/* DPLL rate rounding: minimum DPLL multiplier, divider values */
#define DPLL_MIN_MULTIPLIER             1
#define DPLL_MIN_DIVIDER                1

/* Possible error results from _dpll_test_mult */
#define DPLL_MULT_UNDERFLOW             -1

/*
 * Scale factor to mitigate roundoff errors in DPLL rate rounding.
 * The higher the scale factor, the greater the risk of arithmetic overflow,
 * but the closer the rounded rate to the target rate.  DPLL_SCALE_FACTOR
 * must be a power of DPLL_SCALE_BASE.
 */
#define DPLL_SCALE_FACTOR               64
#define DPLL_SCALE_BASE                 2
#define DPLL_ROUNDING_VAL               ((DPLL_SCALE_BASE / 2) * \
                                         (DPLL_SCALE_FACTOR / DPLL_SCALE_BASE))

/* DPLL valid Fint frequency band limits - from 34xx TRM Section 4.7.6.2 */
#define DPLL_FINT_BAND1_MIN             750000
#define DPLL_FINT_BAND1_MAX             2100000
#define DPLL_FINT_BAND2_MIN             7500000
#define DPLL_FINT_BAND2_MAX             21000000

/* _dpll_test_fint() return codes */
#define DPLL_FINT_UNDERFLOW             -1
#define DPLL_FINT_INVALID               -2

/* Bitmask to isolate the register type of clk.enable_reg */
#define PRCM_REGTYPE_MASK               0xf0
/* various CM register type options */
#define CM_FCLKEN_REGTYPE               0x00
#define CM_ICLKEN_REGTYPE               0x10
#define CM_IDLEST_REGTYPE               0x20

u8 cpu_mask;

/*-------------------------------------------------------------------------
 * OMAP2/3 specific clock functions
 *-------------------------------------------------------------------------*/

/*
 * _omap2_clk_read_reg - read a clock register
 * @clk: struct clk *
 *
 * Given a struct clk *, returns the value of the clock's register.
 */
static u32 _omap2_clk_read_reg(u16 reg_offset, struct clk *clk)
{
        if (clk->prcm_mod & CLK_REG_IN_SCM)
                return omap_ctrl_readl(reg_offset);
        else if (clk->prcm_mod & CLK_REG_IN_PRM)
                return prm_read_mod_reg(clk->prcm_mod & PRCM_MOD_ADDR_MASK,
                                        reg_offset);
        else
                return cm_read_mod_reg(clk->prcm_mod, reg_offset);
}

/*
 * _omap2_clk_write_reg - write a clock's register
 * @v: value to write to the clock's enable_reg
 * @clk: struct clk *
 *
 * Given a register value @v and struct clk * @clk, writes the value of @v to
 * the clock's enable register.  No return value.
 */
static void _omap2_clk_write_reg(u32 v, u16 reg_offset, struct clk *clk)
{
        if (clk->prcm_mod & CLK_REG_IN_SCM)
                omap_ctrl_writel(v, reg_offset);
        else if (clk->prcm_mod & CLK_REG_IN_PRM)
                prm_write_mod_reg(v, clk->prcm_mod & PRCM_MOD_ADDR_MASK,
                                  reg_offset);
        else
                cm_write_mod_reg(v, clk->prcm_mod, reg_offset);
}

/*
 * _dpll_test_fint - test whether an Fint value is valid for the DPLL
 * @clk: DPLL struct clk to test
 * @n: divider value (N) to test
 *
 * Tests whether a particular divider @n will result in a valid DPLL
 * internal clock frequency Fint. See the 34xx TRM 4.7.6.2 "DPLL Jitter
 * Correction".  Returns 0 if OK, -1 if the enclosing loop can terminate
 * (assuming that it is counting N upwards), or -2 if the enclosing loop
 * should skip to the next iteration (again assuming N is increasing).
 */
static int _dpll_test_fint(struct clk *clk, u8 n)
{
        struct dpll_data *dd;
        long fint;
        int ret = 0;

        dd = clk->dpll_data;

        /* DPLL divider must result in a valid jitter correction val */
        fint = clk->parent->rate / (n + 1);
        if (fint < DPLL_FINT_BAND1_MIN) {

                pr_debug("rejecting n=%d due to Fint failure, "
                         "lowering max_divider\n", n);
                dd->max_divider = n;
                ret = DPLL_FINT_UNDERFLOW;

        } else if (fint > DPLL_FINT_BAND1_MAX &&
                   fint < DPLL_FINT_BAND2_MIN) {

                pr_debug("rejecting n=%d due to Fint failure\n", n);
                ret = DPLL_FINT_INVALID;

        } else if (fint > DPLL_FINT_BAND2_MAX) {

                pr_debug("rejecting n=%d due to Fint failure, "
                         "boosting min_divider\n", n);
                dd->min_divider = n;
                ret = DPLL_FINT_INVALID;

        }

        return ret;
}

/**
 * omap2_init_clk_clkdm - look up a clockdomain name, store pointer in clk
 * @clk: OMAP clock struct ptr to use
 *
 * Convert a clockdomain name stored in a struct clk 'clk' into a
 * clockdomain pointer, and save it into the struct clk.  Intended to be
 * called during clk_register().  No return value.
 */
void omap2_init_clk_clkdm(struct clk *clk)
{
        struct clockdomain *clkdm;

        if (!clk->clkdm.name) {
                pr_err("clock: %s: missing clockdomain", clk->name);
                return;
        }

        clkdm = clkdm_lookup(clk->clkdm.name);
        if (clkdm) {
                pr_debug("clock: associated clk %s to clkdm %s\n",
                         clk->name, clk->clkdm.name);
                clk->clkdm.ptr = clkdm;
        } else {
                pr_err("clock: %s: could not associate to clkdm %s\n",
                       clk->name, clk->clkdm.name);
        }
}

/**
 * omap2_init_clksel_parent - set a clksel clk's parent field from the hardware
 * @clk: OMAP clock struct ptr to use
 *
 * Given a pointer to a source-selectable struct clk, read the hardware
 * register and determine what its parent is currently set to.  Update the
 * clk->parent field with the appropriate clk ptr.
 */
void omap2_init_clksel_parent(struct clk *clk)
{
        const struct clksel *clks;
        const struct clksel_rate *clkr;
        u32 r, found = 0;

        if (!clk->clksel)
                return;

        r = _omap2_clk_read_reg(clk->clksel_reg, clk);
        r &= clk->clksel_mask;
        r >>= __ffs(clk->clksel_mask);

        for (clks = clk->clksel; clks->parent && !found; clks++) {
                for (clkr = clks->rates; clkr->div && !found; clkr++) {
                        if ((clkr->flags & cpu_mask) && (clkr->val == r)) {
                                if (clk->parent != clks->parent) {
                                        pr_debug("clock: inited %s parent "
                                                 "to %s (was %s)\n",
                                                 clk->name, clks->parent->name,
                                                 ((clk->parent) ?
                                                  clk->parent->name : "NULL"));
                                        clk->parent = clks->parent;
                                };
                                found = 1;
                        }
                }
        }

        if (!found)
                printk(KERN_ERR "clock: init parent: could not find "
                       "regval %0x for clock %s\n", r,  clk->name);

        return;
}

/**
 * omap2_get_dpll_rate - returns the current DPLL CLKOUT rate
 * @clk: struct clk * of a DPLL
 * @parent_rate: rate of the parent of the DPLL clock
 *
 * DPLLs can be locked or bypassed - basically, enabled or disabled.
 * When locked, the DPLL output depends on the M and N values.  When
 * bypassed, on OMAP2xxx, the output rate is either the 32KiHz clock
 * or sys_clk.  Bypass rates on OMAP3 depend on the DPLL: DPLLs 1 and
 * 2 are bypassed with dpll1_fclk and dpll2_fclk respectively
 * (generated by DPLL3), while DPLL 3, 4, and 5 bypass rates are sys_clk.
 * Returns the current DPLL CLKOUT rate (*not* CLKOUTX2) if the DPLL is
 * locked, or the appropriate bypass rate if the DPLL is bypassed, or 0
 * if the clock @clk is not a DPLL.
 */
u32 omap2_get_dpll_rate(struct clk *clk, unsigned long parent_rate)
{
        long long dpll_clk;
        u32 dpll_mult, dpll_div, v;
        struct dpll_data *dd;

        dd = clk->dpll_data;
        if (!dd)
                return 0;

        /* Return bypass rate if DPLL is bypassed */
        v = cm_read_mod_reg(clk->prcm_mod, dd->control_reg);
        v &= dd->enable_mask;
        v >>= __ffs(dd->enable_mask);

        if (cpu_is_omap24xx()) {

                if (v == OMAP2XXX_EN_DPLL_LPBYPASS ||
                    v == OMAP2XXX_EN_DPLL_FRBYPASS)
                        return parent_rate;

        } else if (cpu_is_omap34xx()) {

                if (v == OMAP3XXX_EN_DPLL_LPBYPASS ||
                    v == OMAP3XXX_EN_DPLL_FRBYPASS)
                        return dd->bypass_clk->rate;

        }

        v = cm_read_mod_reg(clk->prcm_mod, dd->mult_div1_reg);
        dpll_mult = v & dd->mult_mask;
        dpll_mult >>= __ffs(dd->mult_mask);
        dpll_div = v & dd->div1_mask;
        dpll_div >>= __ffs(dd->div1_mask);

        dpll_clk = (long long)parent_rate * dpll_mult;
        do_div(dpll_clk, dpll_div + 1);

        return dpll_clk;
}

/*
 * Used for clocks that have the same value as the parent clock,
 * divided by some factor
 */
void omap2_fixed_divisor_recalc(struct clk *clk, unsigned long parent_rate,
                                u8 rate_storage)
{
        unsigned long rate;

        WARN_ON(!clk->fixed_div); /* XXX move this to init */

        rate = parent_rate / clk->fixed_div;

        if (rate_storage == CURRENT_RATE)
                clk->rate = rate;
        else if (rate_storage == TEMP_RATE)
                clk->temp_rate = rate;
}

/**
 * omap2_wait_clock_ready - wait for clock to enable
 * @prcm_mod: CM submodule offset from CM_BASE (e.g., "MPU_MOD")
 * @reg_index: offset of CM register address from prcm_mod
 * @mask: value to mask against to determine if the clock is active
 * @name: name of the clock (for printk)
 *
 * Returns 1 if the clock enabled in time, or 0 if it failed to enable
 * in roughly MAX_CLOCK_ENABLE_WAIT microseconds.
 */
int omap2_wait_clock_ready(s16 prcm_mod, u16 reg_index, u32 mask,
                           const char *name)
{
        int i = 0, ena = 0;

        /*
         * 24xx uses 0 to indicate not ready, and 1 to indicate ready.
         * 34xx reverses this, just to keep us on our toes
         */
        if (cpu_mask & (RATE_IN_242X | RATE_IN_243X))
                ena = mask;
        else if (cpu_mask & RATE_IN_343X)
                ena = 0;

        /* Wait for lock */
        while (((cm_read_mod_reg(prcm_mod, reg_index) & mask) != ena) &&
               (i++ < MAX_CLOCK_ENABLE_WAIT)) {
                udelay(1);
        }

        if (i < MAX_CLOCK_ENABLE_WAIT)
                pr_debug("Clock %s stable after %d loops\n", name, i);
        else
                printk(KERN_ERR "Clock %s didn't enable in %d tries\n",
                       name, MAX_CLOCK_ENABLE_WAIT);

        return (i < MAX_CLOCK_ENABLE_WAIT) ? 1 : 0;
};


/*
 * omap2_clk_wait_ready - wait for a OMAP module to come out of target idle
 * @clk: struct clk * recently enabled to indicate the module to test
 *
 * Wait for an OMAP module with a target idle state bit to come out of
 * idle once both its interface clock and primary functional clock are
 * both enabled.  Any register read or write to the device before it
 * returns from idle will cause an abort.  Not all modules have target
 * idle state bits (for example, DSS and CAM on OMAP24xx); so we don't
 * wait for those.  No return value.
 *
 * We don't need special code here for INVERT_ENABLE for the time
 * being since INVERT_ENABLE only applies to clocks enabled by
 * CM_CLKEN_PLL.
 *
 * REVISIT: This function is misnamed: it should be something like
 * "omap2_module_wait_ready", and in the long-term, it does not belong
 * in the clock framework. It also shouldn't be doing register
 * arithmetic to determine the companion clock.
 */
static void omap2_clk_wait_ready(struct clk *clk)
{
        u16 other_reg, idlest_reg;
        u32 other_bit;

        if (!(clk->flags & WAIT_READY))
                return;

        /* If we are enabling an iclk, also test the fclk; and vice versa */
        other_bit = 1 << clk->enable_bit;
        other_reg = clk->enable_reg & ~PRCM_REGTYPE_MASK;

        if (clk->enable_reg & CM_ICLKEN_REGTYPE)
                other_reg |= CM_FCLKEN_REGTYPE;
        else
                other_reg |= CM_ICLKEN_REGTYPE;

        /* Ensure functional and interface clocks are running. */
        if (!(cm_read_mod_reg(clk->prcm_mod, other_reg) & other_bit))
                return;

        idlest_reg = other_reg & ~PRCM_REGTYPE_MASK;
        idlest_reg |= CM_IDLEST_REGTYPE;

        omap2_wait_clock_ready(clk->prcm_mod, idlest_reg, 1 << clk->idlest_bit,
                               clk->name);
}

/* Enables clock without considering parent dependencies or use count
 * REVISIT: Maybe change this to use clk->enable like on omap1?
 */
static int _omap2_clk_enable(struct clk *clk)
{
        u32 v;

        if (clk->flags & (ALWAYS_ENABLED | PARENT_CONTROLS_CLOCK))
                return 0;

        if (clk->enable)
                return clk->enable(clk);

        v = _omap2_clk_read_reg(clk->enable_reg, clk);
        if (clk->flags & INVERT_ENABLE)
                v &= ~(1 << clk->enable_bit);
        else
                v |= (1 << clk->enable_bit);
        _omap2_clk_write_reg(v, clk->enable_reg, clk);
        wmb();

        omap2_clk_wait_ready(clk);

        return 0;
}

/* Disables clock without considering parent dependencies or use count */
static void _omap2_clk_disable(struct clk *clk)
{
        u32 v;

        if (clk->flags & (ALWAYS_ENABLED | PARENT_CONTROLS_CLOCK))
                return;

        if (clk->disable) {
                clk->disable(clk);
                return;
        }

        v = _omap2_clk_read_reg(clk->enable_reg, clk);
        if (clk->flags & INVERT_ENABLE)
                v |= (1 << clk->enable_bit);
        else
                v &= ~(1 << clk->enable_bit);
        _omap2_clk_write_reg(v, clk->enable_reg, clk);
        wmb();
}

void omap2_clk_disable(struct clk *clk)
{
        if (clk->usecount > 0 && !(--clk->usecount)) {
                _omap2_clk_disable(clk);
                if (clk->parent)
                        omap2_clk_disable(clk->parent);
                if (clk->clkdm.ptr)
                        omap2_clkdm_clk_disable(clk->clkdm.ptr, clk);

        }
}

int omap2_clk_enable(struct clk *clk)
{
        int ret = 0;

        if (clk->usecount++ == 0) {
                if (clk->parent)
                        ret = omap2_clk_enable(clk->parent);

                if (ret != 0) {
                        clk->usecount--;
                        return ret;
                }

                if (clk->clkdm.ptr)
                        omap2_clkdm_clk_enable(clk->clkdm.ptr, clk);

                ret = _omap2_clk_enable(clk);

                if (ret != 0) {
                        if (clk->clkdm.ptr)
                                omap2_clkdm_clk_disable(clk->clkdm.ptr, clk);

                        if (clk->parent) {
                                omap2_clk_disable(clk->parent);
                                clk->usecount--;
                        }
                }
        }

        return ret;
}

/*
 * Used for clocks that are part of CLKSEL_xyz governed clocks.
 * REVISIT: Maybe change to use clk->enable() functions like on omap1?
 */
void omap2_clksel_recalc(struct clk *clk, unsigned long parent_rate,
                         u8 rate_storage)
{
        u32 div = 0;
        unsigned long rate;

        pr_debug("clock: recalc'ing clksel clk %s\n", clk->name);

        div = omap2_clksel_get_divisor(clk);
        if (div == 0)
                return;

        rate = parent_rate / div;

        if (rate_storage == CURRENT_RATE)
                clk->rate = rate;
        else if (rate_storage == TEMP_RATE)
                clk->temp_rate = rate;

        pr_debug("clock: new clock rate is %ld (div %d)\n", clk->rate, div);
}

/**
 * omap2_get_clksel_by_parent - return clksel struct for a given clk & parent
 * @clk: OMAP struct clk ptr to inspect
 * @src_clk: OMAP struct clk ptr of the parent clk to search for
 *
 * Scan the struct clksel array associated with the clock to find
 * the element associated with the supplied parent clock address.
 * Returns a pointer to the struct clksel on success or NULL on error.
 */
static const struct clksel *omap2_get_clksel_by_parent(struct clk *clk,
                                                       struct clk *src_clk)
{
        const struct clksel *clks;

        if (!clk->clksel)
                return NULL;

        for (clks = clk->clksel; clks->parent; clks++) {
                if (clks->parent == src_clk)
                        break; /* Found the requested parent */
        }

        if (!clks->parent) {
                printk(KERN_ERR "clock: Could not find parent clock %s in "
                       "clksel array of clock %s\n", src_clk->name,
                       clk->name);
                return NULL;
        }

        return clks;
}

/**
 * omap2_clksel_round_rate_div - find divisor for the given clock and rate
 * @clk: OMAP struct clk to use
 * @target_rate: desired clock rate
 * @new_div: ptr to where we should store the divisor
 *
 * Finds 'best' divider value in an array based on the source and target
 * rates.  The divider array must be sorted with smallest divider first.
 * Note that this will not work for clocks which are part of CONFIG_PARTICIPANT,
 * they are only settable as part of virtual_prcm set.
 *
 * Returns the rounded clock rate or returns 0xffffffff on error.
 */
u32 omap2_clksel_round_rate_div(struct clk *clk, unsigned long target_rate,
                                u32 *new_div)
{
        unsigned long test_rate;
        const struct clksel *clks;
        const struct clksel_rate *clkr;
        u32 last_div = 0;

        printk(KERN_INFO "clock: clksel_round_rate_div: %s target_rate %ld\n",
               clk->name, target_rate);

        *new_div = 1;

        clks = omap2_get_clksel_by_parent(clk, clk->parent);
        if (!clks)
                return ~0;

        for (clkr = clks->rates; clkr->div; clkr++) {
                if (!(clkr->flags & cpu_mask))
                    continue;

                /* Sanity check */
                if (clkr->div <= last_div)
                        printk(KERN_ERR "clock: clksel_rate table not sorted "
                               "for clock %s", clk->name);

                last_div = clkr->div;

                test_rate = clk->parent->rate / clkr->div;

                if (test_rate <= target_rate)
                        break; /* found it */
        }

        if (!clkr->div) {
                printk(KERN_ERR "clock: Could not find divisor for target "
                       "rate %ld for clock %s parent %s\n", target_rate,
                       clk->name, clk->parent->name);
                return ~0;
        }

        *new_div = clkr->div;

        printk(KERN_INFO "clock: new_div = %d, new_rate = %ld\n", *new_div,
               (clk->parent->rate / clkr->div));

        return (clk->parent->rate / clkr->div);
}

/**
 * omap2_clksel_round_rate - find rounded rate for the given clock and rate
 * @clk: OMAP struct clk to use
 * @target_rate: desired clock rate
 *
 * Compatibility wrapper for OMAP clock framework
 * Finds best target rate based on the source clock and possible dividers.
 * rates. The divider array must be sorted with smallest divider first.
 * Note that this will not work for clocks which are part of CONFIG_PARTICIPANT,
 * they are only settable as part of virtual_prcm set.
 *
 * Returns the rounded clock rate or returns 0xffffffff on error.
 */
long omap2_clksel_round_rate(struct clk *clk, unsigned long target_rate)
{
        u32 new_div;

        return omap2_clksel_round_rate_div(clk, target_rate, &new_div);
}


/* Given a clock and a rate apply a clock specific rounding function */
long omap2_clk_round_rate(struct clk *clk, unsigned long rate)
{
        if (clk->round_rate != NULL)
                return clk->round_rate(clk, rate);

        if (clk->flags & RATE_FIXED)
                printk(KERN_ERR "clock: generic omap2_clk_round_rate called "
                       "on fixed-rate clock %s\n", clk->name);

        return clk->rate;
}

/**
 * omap2_clksel_to_divisor() - turn clksel field value into integer divider
 * @clk: OMAP struct clk to use
 * @field_val: register field value to find
 *
 * Given a struct clk of a rate-selectable clksel clock, and a register field
 * value to search for, find the corresponding clock divisor.  The register
 * field value should be pre-masked and shifted down so the LSB is at bit 0
 * before calling.  Returns 0 on error
 */
u32 omap2_clksel_to_divisor(struct clk *clk, u32 field_val)
{
        const struct clksel *clks;
        const struct clksel_rate *clkr;

        clks = omap2_get_clksel_by_parent(clk, clk->parent);
        if (!clks)
                return 0;

        for (clkr = clks->rates; clkr->div; clkr++) {
                if ((clkr->flags & cpu_mask) && (clkr->val == field_val))
                        break;
        }

        if (!clkr->div) {
                printk(KERN_ERR "clock: Could not find fieldval %d for "
                       "clock %s parent %s\n", field_val, clk->name,
                       clk->parent->name);
                return 0;
        }

        return clkr->div;
}

/**
 * omap2_divisor_to_clksel() - turn clksel integer divisor into a field value
 * @clk: OMAP struct clk to use
 * @div: integer divisor to search for
 *
 * Given a struct clk of a rate-selectable clksel clock, and a clock divisor,
 * find the corresponding register field value.  The return register value is
 * the value before left-shifting.  Returns 0xffffffff on error
 */
u32 omap2_divisor_to_clksel(struct clk *clk, u32 div)
{
        const struct clksel *clks;
        const struct clksel_rate *clkr;

        /* should never happen */
        WARN_ON(div == 0);

        clks = omap2_get_clksel_by_parent(clk, clk->parent);
        if (!clks)
                return 0;

        for (clkr = clks->rates; clkr->div; clkr++) {
                if ((clkr->flags & cpu_mask) && (clkr->div == div))
                        break;
        }

        if (!clkr->div) {
                printk(KERN_ERR "clock: Could not find divisor %d for "
                       "clock %s parent %s\n", div, clk->name,
                       clk->parent->name);
                return 0;
        }

        return clkr->val;
}

/**
 * omap2_clksel_get_divisor - get current divider applied to parent clock.
 * @clk: OMAP struct clk to use.
 *
 * Returns the integer divisor upon success or 0 on error.
 */
u32 omap2_clksel_get_divisor(struct clk *clk)
{
        u32 v;

        if (!clk->clksel_mask)
                return 0;

        v = _omap2_clk_read_reg(clk->clksel_reg, clk);
        v &= clk->clksel_mask;
        v >>= __ffs(clk->clksel_mask);

        return omap2_clksel_to_divisor(clk, v);
}

int omap2_clksel_set_rate(struct clk *clk, unsigned long rate)
{
        u32 v, field_val, validrate, new_div = 0;

        if (!clk->clksel_mask)
                return -EINVAL;

        validrate = omap2_clksel_round_rate_div(clk, rate, &new_div);
        if (validrate != rate)
               return -EINVAL;

        field_val = omap2_divisor_to_clksel(clk, new_div);
        if (field_val == ~0)
                return -EINVAL;

        v = _omap2_clk_read_reg(clk->clksel_reg, clk);
        v &= ~clk->clksel_mask;
        v |= field_val << __ffs(clk->clksel_mask);
        _omap2_clk_write_reg(v, clk->clksel_reg, clk);

        wmb();

        clk->rate = clk->parent->rate / new_div;

        if (clk->flags & DELAYED_APP && cpu_is_omap24xx()) {
                prm_write_mod_reg(OMAP24XX_VALID_CONFIG,
                        OMAP24XX_GR_MOD, OMAP24XX_PRCM_CLKCFG_CTRL_OFFSET);
                wmb();
        }

        return 0;
}


/* Set the clock rate for a clock source */
int omap2_clk_set_rate(struct clk *clk, unsigned long rate)
{
        int ret = -EINVAL;

        pr_debug("clock: set_rate for clock %s to rate %ld\n", clk->name, rate);

        /* CONFIG_PARTICIPANT clocks are changed only in sets via the
           rate table mechanism, driven by mpu_speed  */
        if (clk->flags & CONFIG_PARTICIPANT)
                return -EINVAL;

        /* dpll_ck, core_ck, virt_prcm_set; plus all clksel clocks */
        if (clk->set_rate != NULL)
                ret = clk->set_rate(clk, rate);

        return ret;
}

/*
 * Converts encoded control register address into a full address
 * On error, the return value (parent_div) will be 0.
 */
static u32 _omap2_clksel_get_src_field(struct clk *src_clk, struct clk *clk,
                                       u32 *field_val)
{
        const struct clksel *clks;
        const struct clksel_rate *clkr;

        clks = omap2_get_clksel_by_parent(clk, src_clk);
        if (!clks)
                return 0;

        for (clkr = clks->rates; clkr->div; clkr++) {
                if (clkr->flags & (cpu_mask | DEFAULT_RATE))
                        break; /* Found the default rate for this platform */
        }

        if (!clkr->div) {
                printk(KERN_ERR "clock: Could not find default rate for "
                       "clock %s parent %s\n", clk->name,
                       src_clk->parent->name);
                return 0;
        }

        /* Should never happen.  Add a clksel mask to the struct clk. */
        WARN_ON(clk->clksel_mask == 0);

        *field_val = clkr->val;

        return clkr->div;
}

int omap2_clk_set_parent(struct clk *clk, struct clk *new_parent)
{
        u32 field_val, v, parent_div;

        if (clk->flags & CONFIG_PARTICIPANT)
                return -EINVAL;

        if (!clk->clksel)
                return -EINVAL;

        parent_div = _omap2_clksel_get_src_field(new_parent, clk, &field_val);
        if (!parent_div)
                return -EINVAL;

        if (clk->usecount > 0)
                _omap2_clk_disable(clk);

        /* Set new source value (previous dividers if any in effect) */
        v = _omap2_clk_read_reg(clk->clksel_reg, clk);
        v &= ~clk->clksel_mask;
        v |= field_val << __ffs(clk->clksel_mask);
        _omap2_clk_write_reg(v, clk->clksel_reg, clk);
        wmb();

        if (clk->flags & DELAYED_APP && cpu_is_omap24xx()) {
                prm_write_mod_reg(OMAP24XX_VALID_CONFIG,
                        OMAP24XX_GR_MOD, OMAP24XX_PRCM_CLKCFG_CTRL_OFFSET);
                wmb();
        }

        if (clk->usecount > 0)
                _omap2_clk_enable(clk);

        clk->parent = new_parent;

        /* CLKSEL clocks follow their parents' rates, divided by a divisor */
        clk->rate = new_parent->rate;

        if (parent_div > 0)
                clk->rate /= parent_div;

        pr_debug("clock: set parent of %s to %s (new rate %ld)\n",
                 clk->name, clk->parent->name, clk->rate);

        return 0;
}

struct clk *omap2_clk_get_parent(struct clk *clk)
{
        return clk->parent;
}

/* DPLL rate rounding code */

/**
 * omap2_dpll_set_rate_tolerance: set the error tolerance during rate rounding
 * @clk: struct clk * of the DPLL
 * @tolerance: maximum rate error tolerance
 *
 * Set the maximum DPLL rate error tolerance for the rate rounding
 * algorithm.  The rate tolerance is an attempt to balance DPLL power
 * saving (the least divider value "n") vs. rate fidelity (the least
 * difference between the desired DPLL target rate and the rounded
 * rate out of the algorithm).  So, increasing the tolerance is likely
 * to decrease DPLL power consumption and increase DPLL rate error.
 * Returns -EINVAL if provided a null clock ptr or a clk that is not a
 * DPLL; or 0 upon success.
 */
int omap2_dpll_set_rate_tolerance(struct clk *clk, unsigned int tolerance)
{
        if (!clk || !clk->dpll_data)
                return -EINVAL;

        clk->dpll_data->rate_tolerance = tolerance;

        return 0;
}

static unsigned long _dpll_compute_new_rate(unsigned long parent_rate,
                                            unsigned int m, unsigned int n)
{
        unsigned long long num;

        num = (unsigned long long)parent_rate * m;
        do_div(num, n);
        return num;
}

/*
 * _dpll_test_mult - test a DPLL multiplier value
 * @m: pointer to the DPLL m (multiplier) value under test
 * @n: current DPLL n (divider) value under test
 * @new_rate: pointer to storage for the resulting rounded rate
 * @target_rate: the desired DPLL rate
 * @parent_rate: the DPLL's parent clock rate
 *
 * This code tests a DPLL multiplier value, ensuring that the
 * resulting rate will not be higher than the target_rate, and that
 * the multiplier value itself is valid for the DPLL.  Initially, the
 * integer pointed to by the m argument should be prescaled by
 * multiplying by DPLL_SCALE_FACTOR.  The code will replace this with
 * a non-scaled m upon return.  This non-scaled m will result in a
 * new_rate as close as possible to target_rate (but not greater than
 * target_rate) given the current (parent_rate, n, prescaled m)
 * triple. Returns DPLL_MULT_UNDERFLOW in the event that the
 * non-scaled m attempted to underflow, which can allow the calling
 * function to bail out early; or 0 upon success.
 */
static int _dpll_test_mult(int *m, int n, unsigned long *new_rate,
                           unsigned long target_rate,
                           unsigned long parent_rate)
{
        int r = 0, carry = 0;

        /* Unscale m and round if necessary */
        if (*m % DPLL_SCALE_FACTOR >= DPLL_ROUNDING_VAL)
                carry = 1;
        *m = (*m / DPLL_SCALE_FACTOR) + carry;

        /*
         * The new rate must be <= the target rate to avoid programming
         * a rate that is impossible for the hardware to handle
         */
        *new_rate = _dpll_compute_new_rate(parent_rate, *m, n);
        if (*new_rate > target_rate) {
                (*m)--;
                *new_rate = 0;
        }

        /* Guard against m underflow */
        if (*m < DPLL_MIN_MULTIPLIER) {
                *m = DPLL_MIN_MULTIPLIER;
                *new_rate = 0;
                r = DPLL_MULT_UNDERFLOW;
        }

        if (*new_rate == 0)
                *new_rate = _dpll_compute_new_rate(parent_rate, *m, n);

        return r;
}

/**
 * omap2_dpll_round_rate - round a target rate for an OMAP DPLL
 * @clk: struct clk * for a DPLL
 * @target_rate: desired DPLL clock rate
 *
 * Given a DPLL, a desired target rate, and a rate tolerance, round
 * the target rate to a possible, programmable rate for this DPLL.
 * Rate tolerance is assumed to be set by the caller before this
 * function is called.  Attempts to select the minimum possible n
 * within the tolerance to reduce power consumption.  Stores the
 * computed (m, n) in the DPLL's dpll_data structure so set_rate()
 * will not need to call this (expensive) function again.  Returns ~0
 * if the target rate cannot be rounded, either because the rate is
 * too low or because the rate tolerance is set too tightly; or the
 * rounded rate upon success.
 */
long omap2_dpll_round_rate(struct clk *clk, unsigned long target_rate)
{
        int m, n, r, e, scaled_max_m;
        unsigned long scaled_rt_rp, new_rate;
        int min_e = -1, min_e_m = -1, min_e_n = -1;
        struct dpll_data *dd;

        if (!clk || !clk->dpll_data)
                return ~0;

        dd = clk->dpll_data;

        pr_debug("clock: starting DPLL round_rate for clock %s, target rate "
                 "%ld\n", clk->name, target_rate);

        scaled_rt_rp = target_rate / (clk->parent->rate / DPLL_SCALE_FACTOR);
        scaled_max_m = dd->max_multiplier * DPLL_SCALE_FACTOR;

        dd->last_rounded_rate = 0;

        for (n = dd->min_divider; n <= dd->max_divider; n++) {

                /* Is the (input clk, divider) pair valid for the DPLL? */
                r = _dpll_test_fint(clk, n);
                if (r == DPLL_FINT_UNDERFLOW)
                        break;
                else if (r == DPLL_FINT_INVALID)
                        continue;

                /* Compute the scaled DPLL multiplier, based on the divider */
                m = scaled_rt_rp * n;

                /*
                 * Since we're counting n up, a m overflow means we
                 * can bail out completely (since as n increases in
                 * the next iteration, there's no way that m can
                 * increase beyond the current m)
                 */
                if (m > scaled_max_m)
                        break;

                r = _dpll_test_mult(&m, n, &new_rate, target_rate,
                                    clk->parent->rate);

                /* m can't be set low enough for this n - try with a larger n */
                if (r == DPLL_MULT_UNDERFLOW)
                        continue;

                e = target_rate - new_rate;
                pr_debug("clock: n = %d: m = %d: rate error is %d "
                         "(new_rate = %ld)\n", n, m, e, new_rate);

                if (min_e == -1 ||
                    min_e >= (int)(abs(e) - dd->rate_tolerance)) {
                        min_e = e;
                        min_e_m = m;
                        min_e_n = n;

                        pr_debug("clock: found new least error %d\n", min_e);

                        /* We found good settings -- bail out now */
                        if (min_e <= dd->rate_tolerance)
                                break;
                }
        }

        if (min_e < 0) {
                pr_debug("clock: error: target rate or tolerance too low\n");
                return ~0;
        }

        dd->last_rounded_m = min_e_m;
        dd->last_rounded_n = min_e_n;
        dd->last_rounded_rate = _dpll_compute_new_rate(clk->parent->rate,
                                                       min_e_m,  min_e_n);

        pr_debug("clock: final least error: e = %d, m = %d, n = %d\n",
                 min_e, min_e_m, min_e_n);
        pr_debug("clock: final rate: %ld  (target rate: %ld)\n",
                 dd->last_rounded_rate, target_rate);

        return dd->last_rounded_rate;
}

/*-------------------------------------------------------------------------
 * Omap2 clock reset and init functions
 *-------------------------------------------------------------------------*/

#ifdef CONFIG_OMAP_RESET_CLOCKS
void omap2_clk_disable_unused(struct clk *clk)
{
        u32 regval32, v;

        v = (clk->flags & INVERT_ENABLE) ? (1 << clk->enable_bit) : 0;

        regval32 = _omap2_clk_read_reg(clk->enable_reg, clk);
        if ((regval32 & (1 << clk->enable_bit)) == v)
                return;

        printk(KERN_INFO "Disabling unused clock \"%s\"\n", clk->name);
        _omap2_clk_disable(clk);
}
#endif