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 */ 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 } 112 113 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 */ 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 */ 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 */ 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 */ 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_hw_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_hw_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 */ 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 if (dd->max_rate && target_rate > dd->max_rate) 305 target_rate = dd->max_rate; 306 307 ref_rate = clk_hw_get_rate(dd->clk_ref); 308 clk_name = clk_hw_get_name(hw); 309 pr_debug("clock: %s: starting DPLL round_rate, target rate %lu\n", 310 clk_name, target_rate); 311 312 scaled_rt_rp = target_rate / (ref_rate / DPLL_SCALE_FACTOR); 313 scaled_max_m = dd->max_multiplier * DPLL_SCALE_FACTOR; 314 315 dd->last_rounded_rate = 0; 316 317 for (n = dd->min_divider; n <= dd->max_divider; n++) { 318 /* Is the (input clk, divider) pair valid for the DPLL? */ 319 r = _dpll_test_fint(clk, n); 320 if (r == DPLL_FINT_UNDERFLOW) 321 break; 322 else if (r == DPLL_FINT_INVALID) 323 continue; 324 325 /* Compute the scaled DPLL multiplier, based on the divider */ 326 m = scaled_rt_rp * n; 327 328 /* 329 * Since we're counting n up, a m overflow means we 330 * can bail out completely (since as n increases in 331 * the next iteration, there's no way that m can 332 * increase beyond the current m) 333 */ 334 if (m > scaled_max_m) 335 break; 336 337 r = _dpll_test_mult(&m, n, &new_rate, target_rate, 338 ref_rate); 339 340 /* m can't be set low enough for this n - try with a larger n */ 341 if (r == DPLL_MULT_UNDERFLOW) 342 continue; 343 344 /* skip rates above our target rate */ 345 delta = target_rate - new_rate; 346 if (delta < 0) 347 continue; 348 349 if (delta < prev_min_delta) { 350 prev_min_delta = delta; 351 min_delta_m = m; 352 min_delta_n = n; 353 } 354 355 pr_debug("clock: %s: m = %d: n = %d: new_rate = %lu\n", 356 clk_name, m, n, new_rate); 357 358 if (delta == 0) 359 break; 360 } 361 362 if (prev_min_delta == LONG_MAX) { 363 pr_debug("clock: %s: cannot round to rate %lu\n", 364 clk_name, target_rate); 365 return ~0; 366 } 367 368 dd->last_rounded_m = min_delta_m; 369 dd->last_rounded_n = min_delta_n; 370 dd->last_rounded_rate = target_rate - prev_min_delta; 371 372 return dd->last_rounded_rate; 373 } 374