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      1 /*	$NetBSD: nouveau_nvkm_subdev_clk_pllgt215.c,v 1.3 2021/12/18 23:45:39 riastradh Exp $	*/
      2 
      3 /*
      4  * Copyright 2010 Red Hat Inc.
      5  *
      6  * Permission is hereby granted, free of charge, to any person obtaining a
      7  * copy of this software and associated documentation files (the "Software"),
      8  * to deal in the Software without restriction, including without limitation
      9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
     10  * and/or sell copies of the Software, and to permit persons to whom the
     11  * Software is furnished to do so, subject to the following conditions:
     12  *
     13  * The above copyright notice and this permission notice shall be included in
     14  * all copies or substantial portions of the Software.
     15  *
     16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
     19  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
     20  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
     21  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
     22  * OTHER DEALINGS IN THE SOFTWARE.
     23  *
     24  * Authors: Ben Skeggs
     25  */
     26 #include <sys/cdefs.h>
     27 __KERNEL_RCSID(0, "$NetBSD: nouveau_nvkm_subdev_clk_pllgt215.c,v 1.3 2021/12/18 23:45:39 riastradh Exp $");
     28 
     29 #include "pll.h"
     30 
     31 #include <subdev/bios.h>
     32 #include <subdev/bios/pll.h>
     33 
     34 int
     35 gt215_pll_calc(struct nvkm_subdev *subdev, struct nvbios_pll *info,
     36 	       u32 freq, int *pN, int *pfN, int *pM, int *P)
     37 {
     38 	u32 best_err = ~0, err;
     39 	int M, lM, hM, N, fN;
     40 
     41 	*P = info->vco1.max_freq / freq;
     42 	if (*P > info->max_p)
     43 		*P = info->max_p;
     44 	if (*P < info->min_p)
     45 		*P = info->min_p;
     46 
     47 	lM = (info->refclk + info->vco1.max_inputfreq) / info->vco1.max_inputfreq;
     48 	lM = max(lM, (int)info->vco1.min_m);
     49 	hM = (info->refclk + info->vco1.min_inputfreq) / info->vco1.min_inputfreq;
     50 	hM = min(hM, (int)info->vco1.max_m);
     51 	lM = min(lM, hM);
     52 
     53 	for (M = lM; M <= hM; M++) {
     54 		u32 tmp = freq * *P * M;
     55 		N  = tmp / info->refclk;
     56 		fN = tmp % info->refclk;
     57 
     58 		if (!pfN) {
     59 			if (fN >= info->refclk / 2)
     60 				N++;
     61 		} else {
     62 			if (fN <  info->refclk / 2)
     63 				N--;
     64 			fN = tmp - (N * info->refclk);
     65 		}
     66 
     67 		if (N < info->vco1.min_n)
     68 			continue;
     69 		if (N > info->vco1.max_n)
     70 			break;
     71 
     72 		err = abs(freq - (info->refclk * N / M / *P));
     73 		if (err < best_err) {
     74 			best_err = err;
     75 			*pN = N;
     76 			*pM = M;
     77 		}
     78 
     79 		if (pfN) {
     80 			*pfN = ((fN << 13) + info->refclk / 2) / info->refclk;
     81 			*pfN = (*pfN - 4096) & 0xffff;
     82 			return freq;
     83 		}
     84 	}
     85 
     86 	if (unlikely(best_err == ~0)) {
     87 		nvkm_error(subdev, "unable to find matching pll values\n");
     88 		return -EINVAL;
     89 	}
     90 
     91 	return info->refclk * *pN / *pM / *P;
     92 }
     93