2 * OMAP2/3/4 DPLL clock functions
4 * Copyright (C) 2005-2008 Texas Instruments, Inc.
5 * Copyright (C) 2004-2010 Nokia Corporation
8 * Richard Woodruff <r-woodruff2@ti.com>
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License version 2 as
13 * published by the Free Software Foundation.
17 #include <linux/kernel.h>
18 #include <linux/errno.h>
19 #include <linux/clk-provider.h>
21 #include <linux/clk/ti.h>
23 #include <asm/div64.h>
27 /* DPLL rate rounding: minimum DPLL multiplier, divider values */
28 #define DPLL_MIN_MULTIPLIER 2
29 #define DPLL_MIN_DIVIDER 1
31 /* Possible error results from _dpll_test_mult */
32 #define DPLL_MULT_UNDERFLOW -1
35 * Scale factor to mitigate roundoff errors in DPLL rate rounding.
36 * The higher the scale factor, the greater the risk of arithmetic overflow,
37 * but the closer the rounded rate to the target rate. DPLL_SCALE_FACTOR
38 * must be a power of DPLL_SCALE_BASE.
40 #define DPLL_SCALE_FACTOR 64
41 #define DPLL_SCALE_BASE 2
42 #define DPLL_ROUNDING_VAL ((DPLL_SCALE_BASE / 2) * \
43 (DPLL_SCALE_FACTOR / DPLL_SCALE_BASE))
46 * DPLL valid Fint frequency range for OMAP36xx and OMAP4xxx.
47 * From device data manual section 4.3 "DPLL and DLL Specifications".
49 #define OMAP3PLUS_DPLL_FINT_JTYPE_MIN 500000
50 #define OMAP3PLUS_DPLL_FINT_JTYPE_MAX 2500000
52 /* _dpll_test_fint() return codes */
53 #define DPLL_FINT_UNDERFLOW -1
54 #define DPLL_FINT_INVALID -2
56 /* Private functions */
59 * _dpll_test_fint - test whether an Fint value is valid for the DPLL
60 * @clk: DPLL struct clk to test
61 * @n: divider value (N) to test
63 * Tests whether a particular divider @n will result in a valid DPLL
64 * internal clock frequency Fint. See the 34xx TRM 4.7.6.2 "DPLL Jitter
65 * Correction". Returns 0 if OK, -1 if the enclosing loop can terminate
66 * (assuming that it is counting N upwards), or -2 if the enclosing loop
67 * should skip to the next iteration (again assuming N is increasing).
69 static int _dpll_test_fint(struct clk_hw_omap *clk, unsigned int n)
72 long fint, fint_min, fint_max;
77 /* DPLL divider must result in a valid jitter correction val */
78 fint = __clk_get_rate(__clk_get_parent(clk->hw.clk)) / n;
80 if (dd->flags & DPLL_J_TYPE) {
81 fint_min = OMAP3PLUS_DPLL_FINT_JTYPE_MIN;
82 fint_max = OMAP3PLUS_DPLL_FINT_JTYPE_MAX;
84 fint_min = ti_clk_get_features()->fint_min;
85 fint_max = ti_clk_get_features()->fint_max;
88 if (!fint_min || !fint_max) {
89 WARN(1, "No fint limits available!\n");
90 return DPLL_FINT_INVALID;
93 if (fint < ti_clk_get_features()->fint_min) {
94 pr_debug("rejecting n=%d due to Fint failure, lowering max_divider\n",
97 ret = DPLL_FINT_UNDERFLOW;
98 } else if (fint > ti_clk_get_features()->fint_max) {
99 pr_debug("rejecting n=%d due to Fint failure, boosting min_divider\n",
102 ret = DPLL_FINT_INVALID;
103 } else if (fint > ti_clk_get_features()->fint_band1_max &&
104 fint < ti_clk_get_features()->fint_band2_min) {
105 pr_debug("rejecting n=%d due to Fint failure\n", n);
106 ret = DPLL_FINT_INVALID;
112 static unsigned long _dpll_compute_new_rate(unsigned long parent_rate,
113 unsigned int m, unsigned int n)
115 unsigned long long num;
117 num = (unsigned long long)parent_rate * m;
123 * _dpll_test_mult - test a DPLL multiplier value
124 * @m: pointer to the DPLL m (multiplier) value under test
125 * @n: current DPLL n (divider) value under test
126 * @new_rate: pointer to storage for the resulting rounded rate
127 * @target_rate: the desired DPLL rate
128 * @parent_rate: the DPLL's parent clock rate
130 * This code tests a DPLL multiplier value, ensuring that the
131 * resulting rate will not be higher than the target_rate, and that
132 * the multiplier value itself is valid for the DPLL. Initially, the
133 * integer pointed to by the m argument should be prescaled by
134 * multiplying by DPLL_SCALE_FACTOR. The code will replace this with
135 * a non-scaled m upon return. This non-scaled m will result in a
136 * new_rate as close as possible to target_rate (but not greater than
137 * target_rate) given the current (parent_rate, n, prescaled m)
138 * triple. Returns DPLL_MULT_UNDERFLOW in the event that the
139 * non-scaled m attempted to underflow, which can allow the calling
140 * function to bail out early; or 0 upon success.
142 static int _dpll_test_mult(int *m, int n, unsigned long *new_rate,
143 unsigned long target_rate,
144 unsigned long parent_rate)
146 int r = 0, carry = 0;
148 /* Unscale m and round if necessary */
149 if (*m % DPLL_SCALE_FACTOR >= DPLL_ROUNDING_VAL)
151 *m = (*m / DPLL_SCALE_FACTOR) + carry;
154 * The new rate must be <= the target rate to avoid programming
155 * a rate that is impossible for the hardware to handle
157 *new_rate = _dpll_compute_new_rate(parent_rate, *m, n);
158 if (*new_rate > target_rate) {
163 /* Guard against m underflow */
164 if (*m < DPLL_MIN_MULTIPLIER) {
165 *m = DPLL_MIN_MULTIPLIER;
167 r = DPLL_MULT_UNDERFLOW;
171 *new_rate = _dpll_compute_new_rate(parent_rate, *m, n);
177 * _omap2_dpll_is_in_bypass - check if DPLL is in bypass mode or not
178 * @v: bitfield value of the DPLL enable
180 * Checks given DPLL enable bitfield to see whether the DPLL is in bypass
181 * mode or not. Returns 1 if the DPLL is in bypass, 0 otherwise.
183 static int _omap2_dpll_is_in_bypass(u32 v)
187 mask = ti_clk_get_features()->dpll_bypass_vals;
190 * Each set bit in the mask corresponds to a bypass value equal
191 * to the bitshift. Go through each set-bit in the mask and
192 * compare against the given register value.
204 /* Public functions */
205 u8 omap2_init_dpll_parent(struct clk_hw *hw)
207 struct clk_hw_omap *clk = to_clk_hw_omap(hw);
209 struct dpll_data *dd;
215 v = ti_clk_ll_ops->clk_readl(dd->control_reg);
216 v &= dd->enable_mask;
217 v >>= __ffs(dd->enable_mask);
219 /* Reparent the struct clk in case the dpll is in bypass */
220 if (_omap2_dpll_is_in_bypass(v))
227 * omap2_get_dpll_rate - returns the current DPLL CLKOUT rate
228 * @clk: struct clk * of a DPLL
230 * DPLLs can be locked or bypassed - basically, enabled or disabled.
231 * When locked, the DPLL output depends on the M and N values. When
232 * bypassed, on OMAP2xxx, the output rate is either the 32KiHz clock
233 * or sys_clk. Bypass rates on OMAP3 depend on the DPLL: DPLLs 1 and
234 * 2 are bypassed with dpll1_fclk and dpll2_fclk respectively
235 * (generated by DPLL3), while DPLL 3, 4, and 5 bypass rates are sys_clk.
236 * Returns the current DPLL CLKOUT rate (*not* CLKOUTX2) if the DPLL is
237 * locked, or the appropriate bypass rate if the DPLL is bypassed, or 0
238 * if the clock @clk is not a DPLL.
240 unsigned long omap2_get_dpll_rate(struct clk_hw_omap *clk)
243 u32 dpll_mult, dpll_div, v;
244 struct dpll_data *dd;
250 /* Return bypass rate if DPLL is bypassed */
251 v = ti_clk_ll_ops->clk_readl(dd->control_reg);
252 v &= dd->enable_mask;
253 v >>= __ffs(dd->enable_mask);
255 if (_omap2_dpll_is_in_bypass(v))
256 return __clk_get_rate(dd->clk_bypass);
258 v = ti_clk_ll_ops->clk_readl(dd->mult_div1_reg);
259 dpll_mult = v & dd->mult_mask;
260 dpll_mult >>= __ffs(dd->mult_mask);
261 dpll_div = v & dd->div1_mask;
262 dpll_div >>= __ffs(dd->div1_mask);
264 dpll_clk = (long long)__clk_get_rate(dd->clk_ref) * dpll_mult;
265 do_div(dpll_clk, dpll_div + 1);
270 /* DPLL rate rounding code */
273 * omap2_dpll_round_rate - round a target rate for an OMAP DPLL
274 * @clk: struct clk * for a DPLL
275 * @target_rate: desired DPLL clock rate
277 * Given a DPLL and a desired target rate, round the target rate to a
278 * possible, programmable rate for this DPLL. Attempts to select the
279 * minimum possible n. Stores the computed (m, n) in the DPLL's
280 * dpll_data structure so set_rate() will not need to call this
281 * (expensive) function again. Returns ~0 if the target rate cannot
282 * be rounded, or the rounded rate upon success.
284 long omap2_dpll_round_rate(struct clk_hw *hw, unsigned long target_rate,
285 unsigned long *parent_rate)
287 struct clk_hw_omap *clk = to_clk_hw_omap(hw);
288 int m, n, r, scaled_max_m;
289 int min_delta_m = INT_MAX, min_delta_n = INT_MAX;
290 unsigned long scaled_rt_rp;
291 unsigned long new_rate = 0;
292 struct dpll_data *dd;
293 unsigned long ref_rate;
295 long prev_min_delta = LONG_MAX;
296 const char *clk_name;
298 if (!clk || !clk->dpll_data)
303 ref_rate = __clk_get_rate(dd->clk_ref);
304 clk_name = __clk_get_name(hw->clk);
305 pr_debug("clock: %s: starting DPLL round_rate, target rate %lu\n",
306 clk_name, target_rate);
308 scaled_rt_rp = target_rate / (ref_rate / DPLL_SCALE_FACTOR);
309 scaled_max_m = dd->max_multiplier * DPLL_SCALE_FACTOR;
311 dd->last_rounded_rate = 0;
313 for (n = dd->min_divider; n <= dd->max_divider; n++) {
314 /* Is the (input clk, divider) pair valid for the DPLL? */
315 r = _dpll_test_fint(clk, n);
316 if (r == DPLL_FINT_UNDERFLOW)
318 else if (r == DPLL_FINT_INVALID)
321 /* Compute the scaled DPLL multiplier, based on the divider */
322 m = scaled_rt_rp * n;
325 * Since we're counting n up, a m overflow means we
326 * can bail out completely (since as n increases in
327 * the next iteration, there's no way that m can
328 * increase beyond the current m)
330 if (m > scaled_max_m)
333 r = _dpll_test_mult(&m, n, &new_rate, target_rate,
336 /* m can't be set low enough for this n - try with a larger n */
337 if (r == DPLL_MULT_UNDERFLOW)
340 /* skip rates above our target rate */
341 delta = target_rate - new_rate;
345 if (delta < prev_min_delta) {
346 prev_min_delta = delta;
351 pr_debug("clock: %s: m = %d: n = %d: new_rate = %lu\n",
352 clk_name, m, n, new_rate);
358 if (prev_min_delta == LONG_MAX) {
359 pr_debug("clock: %s: cannot round to rate %lu\n",
360 clk_name, target_rate);
364 dd->last_rounded_m = min_delta_m;
365 dd->last_rounded_n = min_delta_n;
366 dd->last_rounded_rate = target_rate - prev_min_delta;
368 return dd->last_rounded_rate;