1 /*
2 * OMAP2/3/4 DPLL clock functions
3 *
4 * Copyright (C) 2005-2008 Texas Instruments, Inc.
5 * Copyright (C) 2004-2010 Nokia Corporation
6 *
7 * Contacts:
8 * Richard Woodruff <r-woodruff2@ti.com>
9 * Paul Walmsley
10 *
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.
14 */
15 #undef DEBUG
16
17 #include <linux/kernel.h>
18 #include <linux/errno.h>
19 #include <linux/clk.h>
20 #include <linux/clk-provider.h>
21 #include <linux/io.h>
22 #include <linux/clk/ti.h>
23
24 #include <asm/div64.h>
25
26 #include "clock.h"
27
28 /* DPLL rate rounding: minimum DPLL multiplier, divider values */
29 #define DPLL_MIN_MULTIPLIER 2
30 #define DPLL_MIN_DIVIDER 1
31
32 /* Possible error results from _dpll_test_mult */
33 #define DPLL_MULT_UNDERFLOW -1
34
35 /*
36 * Scale factor to mitigate roundoff errors in DPLL rate rounding.
37 * The higher the scale factor, the greater the risk of arithmetic overflow,
38 * but the closer the rounded rate to the target rate. DPLL_SCALE_FACTOR
39 * must be a power of DPLL_SCALE_BASE.
40 */
41 #define DPLL_SCALE_FACTOR 64
42 #define DPLL_SCALE_BASE 2
43 #define DPLL_ROUNDING_VAL ((DPLL_SCALE_BASE / 2) * \
44 (DPLL_SCALE_FACTOR / DPLL_SCALE_BASE))
45
46 /*
47 * DPLL valid Fint frequency range for OMAP36xx and OMAP4xxx.
48 * From device data manual section 4.3 "DPLL and DLL Specifications".
49 */
50 #define OMAP3PLUS_DPLL_FINT_JTYPE_MIN 500000
51 #define OMAP3PLUS_DPLL_FINT_JTYPE_MAX 2500000
52
53 /* _dpll_test_fint() return codes */
54 #define DPLL_FINT_UNDERFLOW -1
55 #define DPLL_FINT_INVALID -2
56
57 /* Private functions */
58
59 /*
60 * _dpll_test_fint - test whether an Fint value is valid for the DPLL
61 * @clk: DPLL struct clk to test
62 * @n: divider value (N) to test
63 *
64 * Tests whether a particular divider @n will result in a valid DPLL
65 * internal clock frequency Fint. See the 34xx TRM 4.7.6.2 "DPLL Jitter
66 * Correction". Returns 0 if OK, -1 if the enclosing loop can terminate
67 * (assuming that it is counting N upwards), or -2 if the enclosing loop
68 * should skip to the next iteration (again assuming N is increasing).
69 */
_dpll_test_fint(struct clk_hw_omap * clk,unsigned int n)70 static int _dpll_test_fint(struct clk_hw_omap *clk, unsigned int n)
71 {
72 struct dpll_data *dd;
73 long fint, fint_min, fint_max;
74 int ret = 0;
75
76 dd = clk->dpll_data;
77
78 /* DPLL divider must result in a valid jitter correction val */
79 fint = clk_hw_get_rate(clk_hw_get_parent(&clk->hw)) / n;
80
81 if (dd->flags & DPLL_J_TYPE) {
82 fint_min = OMAP3PLUS_DPLL_FINT_JTYPE_MIN;
83 fint_max = OMAP3PLUS_DPLL_FINT_JTYPE_MAX;
84 } else {
85 fint_min = ti_clk_get_features()->fint_min;
86 fint_max = ti_clk_get_features()->fint_max;
87 }
88
89 if (!fint_min || !fint_max) {
90 WARN(1, "No fint limits available!\n");
91 return DPLL_FINT_INVALID;
92 }
93
94 if (fint < ti_clk_get_features()->fint_min) {
95 pr_debug("rejecting n=%d due to Fint failure, lowering max_divider\n",
96 n);
97 dd->max_divider = n;
98 ret = DPLL_FINT_UNDERFLOW;
99 } else if (fint > ti_clk_get_features()->fint_max) {
100 pr_debug("rejecting n=%d due to Fint failure, boosting min_divider\n",
101 n);
102 dd->min_divider = n;
103 ret = DPLL_FINT_INVALID;
104 } else if (fint > ti_clk_get_features()->fint_band1_max &&
105 fint < ti_clk_get_features()->fint_band2_min) {
106 pr_debug("rejecting n=%d due to Fint failure\n", n);
107 ret = DPLL_FINT_INVALID;
108 }
109
110 return ret;
111 }
112
_dpll_compute_new_rate(unsigned long parent_rate,unsigned int m,unsigned int n)113 static unsigned long _dpll_compute_new_rate(unsigned long parent_rate,
114 unsigned int m, unsigned int n)
115 {
116 unsigned long long num;
117
118 num = (unsigned long long)parent_rate * m;
119 do_div(num, n);
120 return num;
121 }
122
123 /*
124 * _dpll_test_mult - test a DPLL multiplier value
125 * @m: pointer to the DPLL m (multiplier) value under test
126 * @n: current DPLL n (divider) value under test
127 * @new_rate: pointer to storage for the resulting rounded rate
128 * @target_rate: the desired DPLL rate
129 * @parent_rate: the DPLL's parent clock rate
130 *
131 * This code tests a DPLL multiplier value, ensuring that the
132 * resulting rate will not be higher than the target_rate, and that
133 * the multiplier value itself is valid for the DPLL. Initially, the
134 * integer pointed to by the m argument should be prescaled by
135 * multiplying by DPLL_SCALE_FACTOR. The code will replace this with
136 * a non-scaled m upon return. This non-scaled m will result in a
137 * new_rate as close as possible to target_rate (but not greater than
138 * target_rate) given the current (parent_rate, n, prescaled m)
139 * triple. Returns DPLL_MULT_UNDERFLOW in the event that the
140 * non-scaled m attempted to underflow, which can allow the calling
141 * function to bail out early; or 0 upon success.
142 */
_dpll_test_mult(int * m,int n,unsigned long * new_rate,unsigned long target_rate,unsigned long parent_rate)143 static int _dpll_test_mult(int *m, int n, unsigned long *new_rate,
144 unsigned long target_rate,
145 unsigned long parent_rate)
146 {
147 int r = 0, carry = 0;
148
149 /* Unscale m and round if necessary */
150 if (*m % DPLL_SCALE_FACTOR >= DPLL_ROUNDING_VAL)
151 carry = 1;
152 *m = (*m / DPLL_SCALE_FACTOR) + carry;
153
154 /*
155 * The new rate must be <= the target rate to avoid programming
156 * a rate that is impossible for the hardware to handle
157 */
158 *new_rate = _dpll_compute_new_rate(parent_rate, *m, n);
159 if (*new_rate > target_rate) {
160 (*m)--;
161 *new_rate = 0;
162 }
163
164 /* Guard against m underflow */
165 if (*m < DPLL_MIN_MULTIPLIER) {
166 *m = DPLL_MIN_MULTIPLIER;
167 *new_rate = 0;
168 r = DPLL_MULT_UNDERFLOW;
169 }
170
171 if (*new_rate == 0)
172 *new_rate = _dpll_compute_new_rate(parent_rate, *m, n);
173
174 return r;
175 }
176
177 /**
178 * _omap2_dpll_is_in_bypass - check if DPLL is in bypass mode or not
179 * @v: bitfield value of the DPLL enable
180 *
181 * Checks given DPLL enable bitfield to see whether the DPLL is in bypass
182 * mode or not. Returns 1 if the DPLL is in bypass, 0 otherwise.
183 */
_omap2_dpll_is_in_bypass(u32 v)184 static int _omap2_dpll_is_in_bypass(u32 v)
185 {
186 u8 mask, val;
187
188 mask = ti_clk_get_features()->dpll_bypass_vals;
189
190 /*
191 * Each set bit in the mask corresponds to a bypass value equal
192 * to the bitshift. Go through each set-bit in the mask and
193 * compare against the given register value.
194 */
195 while (mask) {
196 val = __ffs(mask);
197 mask ^= (1 << val);
198 if (v == val)
199 return 1;
200 }
201
202 return 0;
203 }
204
205 /* Public functions */
omap2_init_dpll_parent(struct clk_hw * hw)206 u8 omap2_init_dpll_parent(struct clk_hw *hw)
207 {
208 struct clk_hw_omap *clk = to_clk_hw_omap(hw);
209 u32 v;
210 struct dpll_data *dd;
211
212 dd = clk->dpll_data;
213 if (!dd)
214 return -EINVAL;
215
216 v = ti_clk_ll_ops->clk_readl(dd->control_reg);
217 v &= dd->enable_mask;
218 v >>= __ffs(dd->enable_mask);
219
220 /* Reparent the struct clk in case the dpll is in bypass */
221 if (_omap2_dpll_is_in_bypass(v))
222 return 1;
223
224 return 0;
225 }
226
227 /**
228 * omap2_get_dpll_rate - returns the current DPLL CLKOUT rate
229 * @clk: struct clk * of a DPLL
230 *
231 * DPLLs can be locked or bypassed - basically, enabled or disabled.
232 * When locked, the DPLL output depends on the M and N values. When
233 * bypassed, on OMAP2xxx, the output rate is either the 32KiHz clock
234 * or sys_clk. Bypass rates on OMAP3 depend on the DPLL: DPLLs 1 and
235 * 2 are bypassed with dpll1_fclk and dpll2_fclk respectively
236 * (generated by DPLL3), while DPLL 3, 4, and 5 bypass rates are sys_clk.
237 * Returns the current DPLL CLKOUT rate (*not* CLKOUTX2) if the DPLL is
238 * locked, or the appropriate bypass rate if the DPLL is bypassed, or 0
239 * if the clock @clk is not a DPLL.
240 */
omap2_get_dpll_rate(struct clk_hw_omap * clk)241 unsigned long omap2_get_dpll_rate(struct clk_hw_omap *clk)
242 {
243 u64 dpll_clk;
244 u32 dpll_mult, dpll_div, v;
245 struct dpll_data *dd;
246
247 dd = clk->dpll_data;
248 if (!dd)
249 return 0;
250
251 /* Return bypass rate if DPLL is bypassed */
252 v = ti_clk_ll_ops->clk_readl(dd->control_reg);
253 v &= dd->enable_mask;
254 v >>= __ffs(dd->enable_mask);
255
256 if (_omap2_dpll_is_in_bypass(v))
257 return clk_get_rate(dd->clk_bypass);
258
259 v = ti_clk_ll_ops->clk_readl(dd->mult_div1_reg);
260 dpll_mult = v & dd->mult_mask;
261 dpll_mult >>= __ffs(dd->mult_mask);
262 dpll_div = v & dd->div1_mask;
263 dpll_div >>= __ffs(dd->div1_mask);
264
265 dpll_clk = (u64)clk_get_rate(dd->clk_ref) * dpll_mult;
266 do_div(dpll_clk, dpll_div + 1);
267
268 return dpll_clk;
269 }
270
271 /* DPLL rate rounding code */
272
273 /**
274 * omap2_dpll_round_rate - round a target rate for an OMAP DPLL
275 * @clk: struct clk * for a DPLL
276 * @target_rate: desired DPLL clock rate
277 *
278 * Given a DPLL and a desired target rate, round the target rate to a
279 * possible, programmable rate for this DPLL. Attempts to select the
280 * minimum possible n. Stores the computed (m, n) in the DPLL's
281 * dpll_data structure so set_rate() will not need to call this
282 * (expensive) function again. Returns ~0 if the target rate cannot
283 * be rounded, or the rounded rate upon success.
284 */
omap2_dpll_round_rate(struct clk_hw * hw,unsigned long target_rate,unsigned long * parent_rate)285 long omap2_dpll_round_rate(struct clk_hw *hw, unsigned long target_rate,
286 unsigned long *parent_rate)
287 {
288 struct clk_hw_omap *clk = to_clk_hw_omap(hw);
289 int m, n, r, scaled_max_m;
290 int min_delta_m = INT_MAX, min_delta_n = INT_MAX;
291 unsigned long scaled_rt_rp;
292 unsigned long new_rate = 0;
293 struct dpll_data *dd;
294 unsigned long ref_rate;
295 long delta;
296 long prev_min_delta = LONG_MAX;
297 const char *clk_name;
298
299 if (!clk || !clk->dpll_data)
300 return ~0;
301
302 dd = clk->dpll_data;
303
304 ref_rate = clk_get_rate(dd->clk_ref);
305 clk_name = clk_hw_get_name(hw);
306 pr_debug("clock: %s: starting DPLL round_rate, target rate %lu\n",
307 clk_name, target_rate);
308
309 scaled_rt_rp = target_rate / (ref_rate / DPLL_SCALE_FACTOR);
310 scaled_max_m = dd->max_multiplier * DPLL_SCALE_FACTOR;
311
312 dd->last_rounded_rate = 0;
313
314 for (n = dd->min_divider; n <= dd->max_divider; n++) {
315 /* Is the (input clk, divider) pair valid for the DPLL? */
316 r = _dpll_test_fint(clk, n);
317 if (r == DPLL_FINT_UNDERFLOW)
318 break;
319 else if (r == DPLL_FINT_INVALID)
320 continue;
321
322 /* Compute the scaled DPLL multiplier, based on the divider */
323 m = scaled_rt_rp * n;
324
325 /*
326 * Since we're counting n up, a m overflow means we
327 * can bail out completely (since as n increases in
328 * the next iteration, there's no way that m can
329 * increase beyond the current m)
330 */
331 if (m > scaled_max_m)
332 break;
333
334 r = _dpll_test_mult(&m, n, &new_rate, target_rate,
335 ref_rate);
336
337 /* m can't be set low enough for this n - try with a larger n */
338 if (r == DPLL_MULT_UNDERFLOW)
339 continue;
340
341 /* skip rates above our target rate */
342 delta = target_rate - new_rate;
343 if (delta < 0)
344 continue;
345
346 if (delta < prev_min_delta) {
347 prev_min_delta = delta;
348 min_delta_m = m;
349 min_delta_n = n;
350 }
351
352 pr_debug("clock: %s: m = %d: n = %d: new_rate = %lu\n",
353 clk_name, m, n, new_rate);
354
355 if (delta == 0)
356 break;
357 }
358
359 if (prev_min_delta == LONG_MAX) {
360 pr_debug("clock: %s: cannot round to rate %lu\n",
361 clk_name, target_rate);
362 return ~0;
363 }
364
365 dd->last_rounded_m = min_delta_m;
366 dd->last_rounded_n = min_delta_n;
367 dd->last_rounded_rate = target_rate - prev_min_delta;
368
369 return dd->last_rounded_rate;
370 }
371