diff options
| -rw-r--r-- | arch/arm/mach-omap2/Makefile | 3 | ||||
| -rw-r--r-- | arch/arm/mach-omap2/clkt_dpll.c | 386 | ||||
| -rw-r--r-- | arch/arm/mach-omap2/clock.c | 355 |
3 files changed, 388 insertions, 356 deletions
diff --git a/arch/arm/mach-omap2/Makefile b/arch/arm/mach-omap2/Makefile index 7d46fde2ce67..1a135c8e7f1e 100644 --- a/arch/arm/mach-omap2/Makefile +++ b/arch/arm/mach-omap2/Makefile @@ -8,7 +8,8 @@ obj-y := id.o io.o control.o mux.o devices.o serial.o gpmc.o timer-gp.o omap-2-3-common = irq.o sdrc.o omap_hwmod.o omap-3-4-common = dpll3xxx.o prcm-common = prcm.o powerdomain.o -clock-common = clock.o clock_common_data.o clockdomain.o +clock-common = clock.o clock_common_data.o \ + clockdomain.o clkt_dpll.o obj-$(CONFIG_ARCH_OMAP2) += $(omap-2-3-common) $(prcm-common) $(clock-common) obj-$(CONFIG_ARCH_OMAP3) += $(omap-2-3-common) $(prcm-common) $(clock-common) \ diff --git a/arch/arm/mach-omap2/clkt_dpll.c b/arch/arm/mach-omap2/clkt_dpll.c new file mode 100644 index 000000000000..9eee0e67d5d6 --- /dev/null +++ b/arch/arm/mach-omap2/clkt_dpll.c @@ -0,0 +1,386 @@ +/* + * 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 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 + +/* 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; +} + diff --git a/arch/arm/mach-omap2/clock.c b/arch/arm/mach-omap2/clock.c index d88b25565a42..98196285e80c 100644 --- a/arch/arm/mach-omap2/clock.c +++ b/arch/arm/mach-omap2/clock.c @@ -28,10 +28,7 @@ #include <plat/clockdomain.h> #include <plat/cpu.h> #include <plat/prcm.h> -#include <asm/div64.h> -#include <plat/sdrc.h> -#include "sdrc.h" #include "clock.h" #include "prm.h" #include "prm-regbits-24xx.h" @@ -39,72 +36,12 @@ #include "cm-regbits-24xx.h" #include "cm-regbits-34xx.h" -/* 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 - u8 cpu_mask; /*------------------------------------------------------------------------- * OMAP2/3/4 specific clock 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; -} - /** * _omap2xxx_clk_commit - commit clock parent/rate changes in hardware * @clk: struct clk * @@ -127,52 +64,6 @@ static void _omap2xxx_clk_commit(struct clk *clk) prm_read_mod_reg(OMAP24XX_GR_MOD, OMAP2_PRCM_CLKCFG_CTRL_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 @@ -243,62 +134,6 @@ void omap2_init_clksel_parent(struct clk *clk) } /** - * 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; -} - -/** * omap2_clk_dflt_find_companion - find companion clock to @clk * @clk: struct clk * to find the companion clock of * @other_reg: void __iomem ** to return the companion clock CM_*CLKEN va in @@ -858,196 +693,6 @@ int omap2_clk_set_parent(struct clk *clk, struct clk *new_parent) return 0; } -/* 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 / (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; -} - /*------------------------------------------------------------------------- * Omap2 clock reset and init functions *-------------------------------------------------------------------------*/ |