linux/arch/arm/mach-omap2/clkt_dpll.c

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/*
* 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 */
OMAP2/3/4 clock: fix DPLL multiplier value errors; also copyrights, includes, documentation The maximum DPLL multiplier (M) values for OMAP2xxx and OMAP3xxx are one increment higher than they should be. See for example the OMAP242x TRM Rev X Section 5.10.6 "Clock Generator Registers" and the OMAP36xx TRM Rev C Table 3-202 "CM_CLKSEL1_PLL". Programming a 0 into the DPLL's M register bitfield is valid for OMAP2/3 and indicates that the DPLL should enter MN-bypass mode. Also, increase the minimum multiplier (M) value for the DPLL rate rounding code from 1 to 2, to ensure that it does not inadvertently put the DPLL into bypass. Note that the register documentation in the OMAP2xxx and OMAP3xxx TRMs does not make clear that the actual DPLL divider value (the "N") is the content of the appropriate register bitfield for the N value, _plus one_. (In other words, an N register bitfield of 0 indicates a DPLL divider value of 1.) This is only clearly documented in the OMAP4430 TRM, in, for example, OMAP4430 TRM Rev A Table 3-1167 "CM_CLKSEL_DPLL_USB". While here, update copyrights, add kerneldoc for struct dpll_data, drop the unused struct dpll_data.max_tolerance field, remove some unnecessary #includes in DPLL-related code, and replace the #include of <linux/module.h> with <linux/list.h>, which is what was really needed. The OMAP4 clock autogenerator script has been updated accordingly. Signed-off-by: Paul Walmsley <paul@pwsan.com> Cc: Benoît Cousson <b-cousson@ti.com> Cc: Rajendra Nayak <rnayak@ti.com>
2010-02-23 06:09:12 +01:00
#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;
}