/*
* OMAP2/3/4 DPLL clock functions
*
* Copyright (C) 2005-2008 Texas Instruments, Inc.
* Copyright (C) 2004-2010 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/kernel.h>
#include <linux/errno.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <asm/div64.h>
#include <plat/clock.h>
#include "clock.h"
#include "cm.h"
#include "cm-regbits-24xx.h"
#include "cm-regbits-34xx.h"
/* DPLL rate rounding: minimum DPLL multiplier, divider values */
#define DPLL_MIN_MULTIPLIER 2
#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
/* Private functions */
/*
* _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;
}
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;
}
/* Public functions */
void omap2_init_dpll_parent(struct clk *clk)
{
u32 v;
struct dpll_data *dd;
dd = clk->dpll_data;
if (!dd)
return;
/* Return bypass rate if DPLL is bypassed */
v = __raw_readl(dd->control_reg);
v &= dd->enable_mask;
v >>= __ffs(dd->enable_mask);
/* Reparent in case the dpll is in bypass */
if (cpu_is_omap24xx()) {
if (v == OMAP2XXX_EN_DPLL_LPBYPASS ||
v == OMAP2XXX_EN_DPLL_FRBYPASS)
clk_reparent(clk, dd->clk_bypass);
} else if (cpu_is_omap34xx()) {
if (v == OMAP3XXX_EN_DPLL_LPBYPASS ||
v == OMAP3XXX_EN_DPLL_FRBYPASS)
clk_reparent(clk, dd->clk_bypass);
} else if (cpu_is_omap44xx()) {
if (v == OMAP4XXX_EN_DPLL_LPBYPASS ||
v == OMAP4XXX_EN_DPLL_FRBYPASS ||
v == OMAP4XXX_EN_DPLL_MNBYPASS)
clk_reparent(clk, dd->clk_bypass);
}
return;
}
/**
* omap2_get_dpll_rate - returns the current DPLL CLKOUT rate
* @clk: struct clk * of a DPLL
*
* 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)
{
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 = __raw_readl(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 dd->clk_bypass->rate;
} else if (cpu_is_omap34xx()) {
if (v == OMAP3XXX_EN_DPLL_LPBYPASS ||
v == OMAP3XXX_EN_DPLL_FRBYPASS)
return dd->clk_bypass->rate;
} else if (cpu_is_omap44xx()) {
if (v == OMAP4XXX_EN_DPLL_LPBYPASS ||
v == OMAP4XXX_EN_DPLL_FRBYPASS ||
v == OMAP4XXX_EN_DPLL_MNBYPASS)
return dd->clk_bypass->rate;
}
v = __raw_readl(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)dd->clk_ref->rate * dpll_mult;
do_div(dpll_clk, dpll_div + 1);
return dpll_clk;
}
/* 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;
}
/**
* 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 / (dd->clk_ref->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,
dd->clk_ref->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(dd->clk_ref->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;
}
