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      1 /* $NetBSD: imx_ccm_div.c,v 1.1 2020/12/23 14:42:38 skrll Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 2020 Jared McNeill <jmcneill (at) invisible.ca>
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     22  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 __KERNEL_RCSID(0, "$NetBSD: imx_ccm_div.c,v 1.1 2020/12/23 14:42:38 skrll Exp $");
     31 
     32 #include <sys/param.h>
     33 #include <sys/bus.h>
     34 
     35 #include <dev/clk/clk_backend.h>
     36 
     37 #include <arm/nxp/imx_ccm.h>
     38 
     39 #include <dev/fdt/fdtvar.h>
     40 
     41 u_int
     42 imx_ccm_div_get_rate(struct imx_ccm_softc *sc,
     43     struct imx_ccm_clk *clk)
     44 {
     45 	struct imx_ccm_div *div = &clk->u.div;
     46 	struct clk *clkp, *clkp_parent;
     47 
     48 	KASSERT(clk->type == IMX_CCM_DIV);
     49 
     50 	clkp = &clk->base;
     51 	clkp_parent = clk_get_parent(clkp);
     52 	if (clkp_parent == NULL)
     53 		return 0;
     54 
     55 	const u_int prate = clk_get_rate(clkp_parent);
     56 	if (prate == 0)
     57 		return 0;
     58 
     59 	const uint32_t val = CCM_READ(sc, clk->regidx, div->reg);
     60 	const u_int n = __SHIFTOUT(val, div->mask);
     61 
     62 	return prate / (n + 1);
     63 }
     64 
     65 int
     66 imx_ccm_div_set_rate(struct imx_ccm_softc *sc,
     67     struct imx_ccm_clk *clk, u_int rate)
     68 {
     69 	struct imx_ccm_div *div = &clk->u.div;
     70 	struct clk *clkp, *clkp_parent;
     71 	int best_diff = INT_MAX;
     72 	u_int n, best_n;
     73 	uint32_t val;
     74 
     75 	KASSERT(clk->type == IMX_CCM_DIV);
     76 
     77 	clkp = &clk->base;
     78 	clkp_parent = clk_get_parent(clkp);
     79 	if (clkp_parent == NULL)
     80 		return ENXIO;
     81 
     82 	if ((div->flags & IMX_DIV_SET_RATE_PARENT) != 0)
     83 		return clk_set_rate(clkp, rate);
     84 
     85 	const u_int prate = clk_get_rate(clkp_parent);
     86 	if (prate == 0)
     87 		return EIO;
     88 
     89 	for (n = 0; n < __SHIFTOUT_MASK(div->mask); n++) {
     90 		const u_int tmp_rate = prate / (n + 1);
     91 		const int diff = (int)rate - (int)tmp_rate;
     92 		if ((div->flags & IMX_DIV_ROUND_DOWN) != 0) {
     93 			if (diff >= 0 && diff < best_diff) {
     94 				best_n = n;
     95 				best_diff = diff;
     96 			}
     97 		} else {
     98 			if (abs(diff) < abs(best_diff)) {
     99 				best_n = n;
    100 				best_diff = abs(diff);
    101 			}
    102 		}
    103 	}
    104 	if (best_diff == INT_MAX)
    105 		return EIO;
    106 
    107 	val = CCM_READ(sc, clk->regidx, div->reg);
    108 	val &= ~div->mask;
    109 	val |= __SHIFTIN(best_n, div->mask);
    110 	CCM_WRITE(sc, clk->regidx, div->reg, val);
    111 
    112 	return 0;
    113 }
    114 
    115 const char *
    116 imx_ccm_div_get_parent(struct imx_ccm_softc *sc,
    117     struct imx_ccm_clk *clk)
    118 {
    119 	struct imx_ccm_div *div = &clk->u.div;
    120 
    121 	KASSERT(clk->type == IMX_CCM_DIV);
    122 
    123 	return div->parent;
    124 }
    125