/* * OMAP2/3/4 DPLL clock functions * * Copyright (C) 2005-2008 Texas Instruments, Inc. * Copyright (C) 2004-2010 Nokia Corporation * * Contacts: * Richard Woodruff * 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 #include #include #include #include #include #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; }