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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/io.h> | |
21 | ||
22 | #include <asm/div64.h> | |
23 | ||
24 | #include <plat/clock.h> | |
25 | ||
26 | #include "clock.h" | |
27 | #include "cm.h" | |
28 | #include "cm-regbits-24xx.h" | |
29 | #include "cm-regbits-34xx.h" | |
30 | ||
31 | /* DPLL rate rounding: minimum DPLL multiplier, divider values */ | |
32 | #define DPLL_MIN_MULTIPLIER 1 | |
33 | #define DPLL_MIN_DIVIDER 1 | |
34 | ||
35 | /* Possible error results from _dpll_test_mult */ | |
36 | #define DPLL_MULT_UNDERFLOW -1 | |
37 | ||
38 | /* | |
39 | * Scale factor to mitigate roundoff errors in DPLL rate rounding. | |
40 | * The higher the scale factor, the greater the risk of arithmetic overflow, | |
41 | * but the closer the rounded rate to the target rate. DPLL_SCALE_FACTOR | |
42 | * must be a power of DPLL_SCALE_BASE. | |
43 | */ | |
44 | #define DPLL_SCALE_FACTOR 64 | |
45 | #define DPLL_SCALE_BASE 2 | |
46 | #define DPLL_ROUNDING_VAL ((DPLL_SCALE_BASE / 2) * \ | |
47 | (DPLL_SCALE_FACTOR / DPLL_SCALE_BASE)) | |
48 | ||
49 | /* DPLL valid Fint frequency band limits - from 34xx TRM Section 4.7.6.2 */ | |
50 | #define DPLL_FINT_BAND1_MIN 750000 | |
51 | #define DPLL_FINT_BAND1_MAX 2100000 | |
52 | #define DPLL_FINT_BAND2_MIN 7500000 | |
53 | #define DPLL_FINT_BAND2_MAX 21000000 | |
54 | ||
55 | /* _dpll_test_fint() return codes */ | |
56 | #define DPLL_FINT_UNDERFLOW -1 | |
57 | #define DPLL_FINT_INVALID -2 | |
58 | ||
59 | /* Private functions */ | |
60 | ||
61 | /* | |
62 | * _dpll_test_fint - test whether an Fint value is valid for the DPLL | |
63 | * @clk: DPLL struct clk to test | |
64 | * @n: divider value (N) to test | |
65 | * | |
66 | * Tests whether a particular divider @n will result in a valid DPLL | |
67 | * internal clock frequency Fint. See the 34xx TRM 4.7.6.2 "DPLL Jitter | |
68 | * Correction". Returns 0 if OK, -1 if the enclosing loop can terminate | |
69 | * (assuming that it is counting N upwards), or -2 if the enclosing loop | |
70 | * should skip to the next iteration (again assuming N is increasing). | |
71 | */ | |
72 | static int _dpll_test_fint(struct clk *clk, u8 n) | |
73 | { | |
74 | struct dpll_data *dd; | |
75 | long fint; | |
76 | int ret = 0; | |
77 | ||
78 | dd = clk->dpll_data; | |
79 | ||
80 | /* DPLL divider must result in a valid jitter correction val */ | |
81 | fint = clk->parent->rate / (n + 1); | |
82 | if (fint < DPLL_FINT_BAND1_MIN) { | |
83 | ||
84 | pr_debug("rejecting n=%d due to Fint failure, " | |
85 | "lowering max_divider\n", n); | |
86 | dd->max_divider = n; | |
87 | ret = DPLL_FINT_UNDERFLOW; | |
88 | ||
89 | } else if (fint > DPLL_FINT_BAND1_MAX && | |
90 | fint < DPLL_FINT_BAND2_MIN) { | |
91 | ||
92 | pr_debug("rejecting n=%d due to Fint failure\n", n); | |
93 | ret = DPLL_FINT_INVALID; | |
94 | ||
95 | } else if (fint > DPLL_FINT_BAND2_MAX) { | |
96 | ||
97 | pr_debug("rejecting n=%d due to Fint failure, " | |
98 | "boosting min_divider\n", n); | |
99 | dd->min_divider = n; | |
100 | ret = DPLL_FINT_INVALID; | |
101 | ||
102 | } | |
103 | ||
104 | return ret; | |
105 | } | |
106 | ||
107 | static unsigned long _dpll_compute_new_rate(unsigned long parent_rate, | |
108 | unsigned int m, unsigned int n) | |
109 | { | |
110 | unsigned long long num; | |
111 | ||
112 | num = (unsigned long long)parent_rate * m; | |
113 | do_div(num, n); | |
114 | return num; | |
115 | } | |
116 | ||
117 | /* | |
118 | * _dpll_test_mult - test a DPLL multiplier value | |
119 | * @m: pointer to the DPLL m (multiplier) value under test | |
120 | * @n: current DPLL n (divider) value under test | |
121 | * @new_rate: pointer to storage for the resulting rounded rate | |
122 | * @target_rate: the desired DPLL rate | |
123 | * @parent_rate: the DPLL's parent clock rate | |
124 | * | |
125 | * This code tests a DPLL multiplier value, ensuring that the | |
126 | * resulting rate will not be higher than the target_rate, and that | |
127 | * the multiplier value itself is valid for the DPLL. Initially, the | |
128 | * integer pointed to by the m argument should be prescaled by | |
129 | * multiplying by DPLL_SCALE_FACTOR. The code will replace this with | |
130 | * a non-scaled m upon return. This non-scaled m will result in a | |
131 | * new_rate as close as possible to target_rate (but not greater than | |
132 | * target_rate) given the current (parent_rate, n, prescaled m) | |
133 | * triple. Returns DPLL_MULT_UNDERFLOW in the event that the | |
134 | * non-scaled m attempted to underflow, which can allow the calling | |
135 | * function to bail out early; or 0 upon success. | |
136 | */ | |
137 | static int _dpll_test_mult(int *m, int n, unsigned long *new_rate, | |
138 | unsigned long target_rate, | |
139 | unsigned long parent_rate) | |
140 | { | |
141 | int r = 0, carry = 0; | |
142 | ||
143 | /* Unscale m and round if necessary */ | |
144 | if (*m % DPLL_SCALE_FACTOR >= DPLL_ROUNDING_VAL) | |
145 | carry = 1; | |
146 | *m = (*m / DPLL_SCALE_FACTOR) + carry; | |
147 | ||
148 | /* | |
149 | * The new rate must be <= the target rate to avoid programming | |
150 | * a rate that is impossible for the hardware to handle | |
151 | */ | |
152 | *new_rate = _dpll_compute_new_rate(parent_rate, *m, n); | |
153 | if (*new_rate > target_rate) { | |
154 | (*m)--; | |
155 | *new_rate = 0; | |
156 | } | |
157 | ||
158 | /* Guard against m underflow */ | |
159 | if (*m < DPLL_MIN_MULTIPLIER) { | |
160 | *m = DPLL_MIN_MULTIPLIER; | |
161 | *new_rate = 0; | |
162 | r = DPLL_MULT_UNDERFLOW; | |
163 | } | |
164 | ||
165 | if (*new_rate == 0) | |
166 | *new_rate = _dpll_compute_new_rate(parent_rate, *m, n); | |
167 | ||
168 | return r; | |
169 | } | |
170 | ||
171 | /* Public functions */ | |
172 | ||
173 | void omap2_init_dpll_parent(struct clk *clk) | |
174 | { | |
175 | u32 v; | |
176 | struct dpll_data *dd; | |
177 | ||
178 | dd = clk->dpll_data; | |
179 | if (!dd) | |
180 | return; | |
181 | ||
182 | /* Return bypass rate if DPLL is bypassed */ | |
183 | v = __raw_readl(dd->control_reg); | |
184 | v &= dd->enable_mask; | |
185 | v >>= __ffs(dd->enable_mask); | |
186 | ||
187 | /* Reparent in case the dpll is in bypass */ | |
188 | if (cpu_is_omap24xx()) { | |
189 | if (v == OMAP2XXX_EN_DPLL_LPBYPASS || | |
190 | v == OMAP2XXX_EN_DPLL_FRBYPASS) | |
191 | clk_reparent(clk, dd->clk_bypass); | |
192 | } else if (cpu_is_omap34xx()) { | |
193 | if (v == OMAP3XXX_EN_DPLL_LPBYPASS || | |
194 | v == OMAP3XXX_EN_DPLL_FRBYPASS) | |
195 | clk_reparent(clk, dd->clk_bypass); | |
196 | } else if (cpu_is_omap44xx()) { | |
197 | if (v == OMAP4XXX_EN_DPLL_LPBYPASS || | |
198 | v == OMAP4XXX_EN_DPLL_FRBYPASS || | |
199 | v == OMAP4XXX_EN_DPLL_MNBYPASS) | |
200 | clk_reparent(clk, dd->clk_bypass); | |
201 | } | |
202 | return; | |
203 | } | |
204 | ||
205 | /** | |
206 | * omap2_get_dpll_rate - returns the current DPLL CLKOUT rate | |
207 | * @clk: struct clk * of a DPLL | |
208 | * | |
209 | * DPLLs can be locked or bypassed - basically, enabled or disabled. | |
210 | * When locked, the DPLL output depends on the M and N values. When | |
211 | * bypassed, on OMAP2xxx, the output rate is either the 32KiHz clock | |
212 | * or sys_clk. Bypass rates on OMAP3 depend on the DPLL: DPLLs 1 and | |
213 | * 2 are bypassed with dpll1_fclk and dpll2_fclk respectively | |
214 | * (generated by DPLL3), while DPLL 3, 4, and 5 bypass rates are sys_clk. | |
215 | * Returns the current DPLL CLKOUT rate (*not* CLKOUTX2) if the DPLL is | |
216 | * locked, or the appropriate bypass rate if the DPLL is bypassed, or 0 | |
217 | * if the clock @clk is not a DPLL. | |
218 | */ | |
219 | u32 omap2_get_dpll_rate(struct clk *clk) | |
220 | { | |
221 | long long dpll_clk; | |
222 | u32 dpll_mult, dpll_div, v; | |
223 | struct dpll_data *dd; | |
224 | ||
225 | dd = clk->dpll_data; | |
226 | if (!dd) | |
227 | return 0; | |
228 | ||
229 | /* Return bypass rate if DPLL is bypassed */ | |
230 | v = __raw_readl(dd->control_reg); | |
231 | v &= dd->enable_mask; | |
232 | v >>= __ffs(dd->enable_mask); | |
233 | ||
234 | if (cpu_is_omap24xx()) { | |
235 | if (v == OMAP2XXX_EN_DPLL_LPBYPASS || | |
236 | v == OMAP2XXX_EN_DPLL_FRBYPASS) | |
237 | return dd->clk_bypass->rate; | |
238 | } else if (cpu_is_omap34xx()) { | |
239 | if (v == OMAP3XXX_EN_DPLL_LPBYPASS || | |
240 | v == OMAP3XXX_EN_DPLL_FRBYPASS) | |
241 | return dd->clk_bypass->rate; | |
242 | } else if (cpu_is_omap44xx()) { | |
243 | if (v == OMAP4XXX_EN_DPLL_LPBYPASS || | |
244 | v == OMAP4XXX_EN_DPLL_FRBYPASS || | |
245 | v == OMAP4XXX_EN_DPLL_MNBYPASS) | |
246 | return dd->clk_bypass->rate; | |
247 | } | |
248 | ||
249 | v = __raw_readl(dd->mult_div1_reg); | |
250 | dpll_mult = v & dd->mult_mask; | |
251 | dpll_mult >>= __ffs(dd->mult_mask); | |
252 | dpll_div = v & dd->div1_mask; | |
253 | dpll_div >>= __ffs(dd->div1_mask); | |
254 | ||
255 | dpll_clk = (long long)dd->clk_ref->rate * dpll_mult; | |
256 | do_div(dpll_clk, dpll_div + 1); | |
257 | ||
258 | return dpll_clk; | |
259 | } | |
260 | ||
261 | /* DPLL rate rounding code */ | |
262 | ||
263 | /** | |
264 | * omap2_dpll_set_rate_tolerance: set the error tolerance during rate rounding | |
265 | * @clk: struct clk * of the DPLL | |
266 | * @tolerance: maximum rate error tolerance | |
267 | * | |
268 | * Set the maximum DPLL rate error tolerance for the rate rounding | |
269 | * algorithm. The rate tolerance is an attempt to balance DPLL power | |
270 | * saving (the least divider value "n") vs. rate fidelity (the least | |
271 | * difference between the desired DPLL target rate and the rounded | |
272 | * rate out of the algorithm). So, increasing the tolerance is likely | |
273 | * to decrease DPLL power consumption and increase DPLL rate error. | |
274 | * Returns -EINVAL if provided a null clock ptr or a clk that is not a | |
275 | * DPLL; or 0 upon success. | |
276 | */ | |
277 | int omap2_dpll_set_rate_tolerance(struct clk *clk, unsigned int tolerance) | |
278 | { | |
279 | if (!clk || !clk->dpll_data) | |
280 | return -EINVAL; | |
281 | ||
282 | clk->dpll_data->rate_tolerance = tolerance; | |
283 | ||
284 | return 0; | |
285 | } | |
286 | ||
287 | /** | |
288 | * omap2_dpll_round_rate - round a target rate for an OMAP DPLL | |
289 | * @clk: struct clk * for a DPLL | |
290 | * @target_rate: desired DPLL clock rate | |
291 | * | |
292 | * Given a DPLL, a desired target rate, and a rate tolerance, round | |
293 | * the target rate to a possible, programmable rate for this DPLL. | |
294 | * Rate tolerance is assumed to be set by the caller before this | |
295 | * function is called. Attempts to select the minimum possible n | |
296 | * within the tolerance to reduce power consumption. Stores the | |
297 | * computed (m, n) in the DPLL's dpll_data structure so set_rate() | |
298 | * will not need to call this (expensive) function again. Returns ~0 | |
299 | * if the target rate cannot be rounded, either because the rate is | |
300 | * too low or because the rate tolerance is set too tightly; or the | |
301 | * rounded rate upon success. | |
302 | */ | |
303 | long omap2_dpll_round_rate(struct clk *clk, unsigned long target_rate) | |
304 | { | |
305 | int m, n, r, e, scaled_max_m; | |
306 | unsigned long scaled_rt_rp, new_rate; | |
307 | int min_e = -1, min_e_m = -1, min_e_n = -1; | |
308 | struct dpll_data *dd; | |
309 | ||
310 | if (!clk || !clk->dpll_data) | |
311 | return ~0; | |
312 | ||
313 | dd = clk->dpll_data; | |
314 | ||
315 | pr_debug("clock: starting DPLL round_rate for clock %s, target rate " | |
316 | "%ld\n", clk->name, target_rate); | |
317 | ||
318 | scaled_rt_rp = target_rate / (dd->clk_ref->rate / DPLL_SCALE_FACTOR); | |
319 | scaled_max_m = dd->max_multiplier * DPLL_SCALE_FACTOR; | |
320 | ||
321 | dd->last_rounded_rate = 0; | |
322 | ||
323 | for (n = dd->min_divider; n <= dd->max_divider; n++) { | |
324 | ||
325 | /* Is the (input clk, divider) pair valid for the DPLL? */ | |
326 | r = _dpll_test_fint(clk, n); | |
327 | if (r == DPLL_FINT_UNDERFLOW) | |
328 | break; | |
329 | else if (r == DPLL_FINT_INVALID) | |
330 | continue; | |
331 | ||
332 | /* Compute the scaled DPLL multiplier, based on the divider */ | |
333 | m = scaled_rt_rp * n; | |
334 | ||
335 | /* | |
336 | * Since we're counting n up, a m overflow means we | |
337 | * can bail out completely (since as n increases in | |
338 | * the next iteration, there's no way that m can | |
339 | * increase beyond the current m) | |
340 | */ | |
341 | if (m > scaled_max_m) | |
342 | break; | |
343 | ||
344 | r = _dpll_test_mult(&m, n, &new_rate, target_rate, | |
345 | dd->clk_ref->rate); | |
346 | ||
347 | /* m can't be set low enough for this n - try with a larger n */ | |
348 | if (r == DPLL_MULT_UNDERFLOW) | |
349 | continue; | |
350 | ||
351 | e = target_rate - new_rate; | |
352 | pr_debug("clock: n = %d: m = %d: rate error is %d " | |
353 | "(new_rate = %ld)\n", n, m, e, new_rate); | |
354 | ||
355 | if (min_e == -1 || | |
356 | min_e >= (int)(abs(e) - dd->rate_tolerance)) { | |
357 | min_e = e; | |
358 | min_e_m = m; | |
359 | min_e_n = n; | |
360 | ||
361 | pr_debug("clock: found new least error %d\n", min_e); | |
362 | ||
363 | /* We found good settings -- bail out now */ | |
364 | if (min_e <= dd->rate_tolerance) | |
365 | break; | |
366 | } | |
367 | } | |
368 | ||
369 | if (min_e < 0) { | |
370 | pr_debug("clock: error: target rate or tolerance too low\n"); | |
371 | return ~0; | |
372 | } | |
373 | ||
374 | dd->last_rounded_m = min_e_m; | |
375 | dd->last_rounded_n = min_e_n; | |
376 | dd->last_rounded_rate = _dpll_compute_new_rate(dd->clk_ref->rate, | |
377 | min_e_m, min_e_n); | |
378 | ||
379 | pr_debug("clock: final least error: e = %d, m = %d, n = %d\n", | |
380 | min_e, min_e_m, min_e_n); | |
381 | pr_debug("clock: final rate: %ld (target rate: %ld)\n", | |
382 | dd->last_rounded_rate, target_rate); | |
383 | ||
384 | return dd->last_rounded_rate; | |
385 | } | |
386 |