drivers/clk/tegra/cvb.c

   1 /*
   2  * Utility functions for parsing Tegra CVB voltage tables
   3  *
   4  * Copyright (C) 2012-2014 NVIDIA Corporation.  All rights reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  13  * more details.
  14  *
  15  */
  16 #include <linux/err.h>
  17 #include <linux/kernel.h>
  18 #include <linux/pm_opp.h>
  19
  20 #include "cvb.h"
  21
  22 /* cvb_mv = ((c2 * speedo / s_scale + c1) * speedo / s_scale + c0) */
  23 static inline int get_cvb_voltage(int speedo, int s_scale,
  24                                   const struct cvb_coefficients *cvb)
  25 {
  26         int mv;
  27
  28         /* apply only speedo scale: output mv = cvb_mv * v_scale */
  29         mv = DIV_ROUND_CLOSEST(cvb->c2 * speedo, s_scale);
  30         mv = DIV_ROUND_CLOSEST((mv + cvb->c1) * speedo, s_scale) + cvb->c0;
  31         return mv;
  32 }
  33
  34 static int round_cvb_voltage(int mv, int v_scale,
  35                              const struct rail_alignment *align)
  36 {
  37         /* combined: apply voltage scale and round to cvb alignment step */
  38         int uv;
  39         int step = (align->step_uv ? : 1000) * v_scale;
  40         int offset = align->offset_uv * v_scale;
  41
  42         uv = max(mv * 1000, offset) - offset;
  43         uv = DIV_ROUND_UP(uv, step) * align->step_uv + align->offset_uv;
  44         return uv / 1000;
  45 }
  46
  47 enum {
  48         DOWN,
  49         UP
  50 };
  51
  52 static int round_voltage(int mv, const struct rail_alignment *align, int up)
  53 {
  54         if (align->step_uv) {
  55                 int uv;
  56
  57                 uv = max(mv * 1000, align->offset_uv) - align->offset_uv;
  58                 uv = (uv + (up ? align->step_uv - 1 : 0)) / align->step_uv;
  59                 return (uv * align->step_uv + align->offset_uv) / 1000;
  60         }
  61         return mv;
  62 }
  63
  64 static int build_opp_table(const struct cvb_table *d,
  65                            int speedo_value,
  66                            unsigned long max_freq,
  67                            struct device *opp_dev)
  68 {
  69         int i, ret, dfll_mv, min_mv, max_mv;
  70         const struct cvb_table_freq_entry *table = NULL;
  71         const struct rail_alignment *align = &d->alignment;
  72
  73         min_mv = round_voltage(d->min_millivolts, align, UP);
  74         max_mv = round_voltage(d->max_millivolts, align, DOWN);
  75
  76         for (i = 0; i < MAX_DVFS_FREQS; i++) {
  77                 table = &d->cvb_table[i];
  78                 if (!table->freq || (table->freq > max_freq))
  79                         break;
  80
  81                 dfll_mv = get_cvb_voltage(
  82                         speedo_value, d->speedo_scale, &table->coefficients);
  83                 dfll_mv = round_cvb_voltage(dfll_mv, d->voltage_scale, align);
  84                 dfll_mv = clamp(dfll_mv, min_mv, max_mv);
  85
  86                 ret = dev_pm_opp_add(opp_dev, table->freq, dfll_mv * 1000);
  87                 if (ret)
  88                         return ret;
  89         }
  90
  91         return 0;
  92 }
  93
  94 /**
  95  * tegra_cvb_build_opp_table - build OPP table from Tegra CVB tables
  96  * @cvb_tables: array of CVB tables
  97  * @sz: size of the previously mentioned array
  98  * @process_id: process id of the HW module
  99  * @speedo_id: speedo id of the HW module
 100  * @speedo_value: speedo value of the HW module
 101  * @max_rate: highest safe clock rate
 102  * @opp_dev: the struct device * for which the OPP table is built
 103  *
 104  * On Tegra, a CVB table encodes the relationship between operating voltage
 105  * and safe maximal frequency for a given module (e.g. GPU or CPU). This
 106  * function calculates the optimal voltage-frequency operating points
 107  * for the given arguments and exports them via the OPP library for the
 108  * given @opp_dev. Returns a pointer to the struct cvb_table that matched
 109  * or an ERR_PTR on failure.
 110  */
 111 const struct cvb_table *tegra_cvb_build_opp_table(
 112                 const struct cvb_table *cvb_tables,
 113                 size_t sz, int process_id,
 114                 int speedo_id, int speedo_value,
 115                 unsigned long max_rate,
 116                 struct device *opp_dev)
 117 {
 118         int i, ret;
 119
 120         for (i = 0; i < sz; i++) {
 121                 const struct cvb_table *d = &cvb_tables[i];
 122
 123                 if (d->speedo_id != -1 && d->speedo_id != speedo_id)
 124                         continue;
 125                 if (d->process_id != -1 && d->process_id != process_id)
 126                         continue;
 127
 128                 ret = build_opp_table(d, speedo_value, max_rate, opp_dev);
 129                 return ret ? ERR_PTR(ret) : d;
 130         }
 131
 132         return ERR_PTR(-EINVAL);
 133 }