drivers/cpufreq/tegra-cpufreq.c

   1 /*
   2  * Copyright (C) 2010 Google, Inc.
   3  *
   4  * Author:
   5  *      Colin Cross <ccross@google.com>
   6  *      Based on arch/arm/plat-omap/cpu-omap.c, (C) 2005 Nokia Corporation
   7  *
   8  * This software is licensed under the terms of the GNU General Public
   9  * License version 2, as published by the Free Software Foundation, and
  10  * may be copied, distributed, and modified under those terms.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  */
  18
  19 #include <linux/kernel.h>
  20 #include <linux/module.h>
  21 #include <linux/types.h>
  22 #include <linux/sched.h>
  23 #include <linux/cpufreq.h>
  24 #include <linux/delay.h>
  25 #include <linux/init.h>
  26 #include <linux/err.h>
  27 #include <linux/clk.h>
  28 #include <linux/io.h>
  29
  30 static struct cpufreq_frequency_table freq_table[] = {
  31         { .frequency = 216000 },
  32         { .frequency = 312000 },
  33         { .frequency = 456000 },
  34         { .frequency = 608000 },
  35         { .frequency = 760000 },
  36         { .frequency = 816000 },
  37         { .frequency = 912000 },
  38         { .frequency = 1000000 },
  39         { .frequency = CPUFREQ_TABLE_END },
  40 };
  41
  42 #define NUM_CPUS        2
  43
  44 static struct clk *cpu_clk;
  45 static struct clk *pll_x_clk;
  46 static struct clk *pll_p_clk;
  47 static struct clk *emc_clk;
  48 static bool pll_x_prepared;
  49
  50 static unsigned int tegra_get_intermediate(struct cpufreq_policy *policy,
  51                                            unsigned int index)
  52 {
  53         unsigned int ifreq = clk_get_rate(pll_p_clk) / 1000;
  54
  55         /*
  56          * Don't switch to intermediate freq if:
  57          * - we are already at it, i.e. policy->cur == ifreq
  58          * - index corresponds to ifreq
  59          */
  60         if ((freq_table[index].frequency == ifreq) || (policy->cur == ifreq))
  61                 return 0;
  62
  63         return ifreq;
  64 }
  65
  66 static int tegra_target_intermediate(struct cpufreq_policy *policy,
  67                                      unsigned int index)
  68 {
  69         int ret;
  70
  71         /*
  72          * Take an extra reference to the main pll so it doesn't turn
  73          * off when we move the cpu off of it as enabling it again while we
  74          * switch to it from tegra_target() would take additional time.
  75          *
  76          * When target-freq is equal to intermediate freq we don't need to
  77          * switch to an intermediate freq and so this routine isn't called.
  78          * Also, we wouldn't be using pll_x anymore and must not take extra
  79          * reference to it, as it can be disabled now to save some power.
  80          */
  81         clk_prepare_enable(pll_x_clk);
  82
  83         ret = clk_set_parent(cpu_clk, pll_p_clk);
  84         if (ret)
  85                 clk_disable_unprepare(pll_x_clk);
  86         else
  87                 pll_x_prepared = true;
  88
  89         return ret;
  90 }
  91
  92 static int tegra_target(struct cpufreq_policy *policy, unsigned int index)
  93 {
  94         unsigned long rate = freq_table[index].frequency;
  95         unsigned int ifreq = clk_get_rate(pll_p_clk) / 1000;
  96         int ret = 0;
  97
  98         /*
  99          * Vote on memory bus frequency based on cpu frequency
 100          * This sets the minimum frequency, display or avp may request higher
 101          */
 102         if (rate >= 816000)
 103                 clk_set_rate(emc_clk, 600000000); /* cpu 816 MHz, emc max */
 104         else if (rate >= 456000)
 105                 clk_set_rate(emc_clk, 300000000); /* cpu 456 MHz, emc 150Mhz */
 106         else
 107                 clk_set_rate(emc_clk, 100000000);  /* emc 50Mhz */
 108
 109         /*
 110          * target freq == pll_p, don't need to take extra reference to pll_x_clk
 111          * as it isn't used anymore.
 112          */
 113         if (rate == ifreq)
 114                 return clk_set_parent(cpu_clk, pll_p_clk);
 115
 116         ret = clk_set_rate(pll_x_clk, rate * 1000);
 117         /* Restore to earlier frequency on error, i.e. pll_x */
 118         if (ret)
 119                 pr_err("Failed to change pll_x to %lu\n", rate);
 120
 121         ret = clk_set_parent(cpu_clk, pll_x_clk);
 122         /* This shouldn't fail while changing or restoring */
 123         WARN_ON(ret);
 124
 125         /*
 126          * Drop count to pll_x clock only if we switched to intermediate freq
 127          * earlier while transitioning to a target frequency.
 128          */
 129         if (pll_x_prepared) {
 130                 clk_disable_unprepare(pll_x_clk);
 131                 pll_x_prepared = false;
 132         }
 133
 134         return ret;
 135 }
 136
 137 static int tegra_cpu_init(struct cpufreq_policy *policy)
 138 {
 139         int ret;
 140
 141         if (policy->cpu >= NUM_CPUS)
 142                 return -EINVAL;
 143
 144         clk_prepare_enable(emc_clk);
 145         clk_prepare_enable(cpu_clk);
 146
 147         /* FIXME: what's the actual transition time? */
 148         ret = cpufreq_generic_init(policy, freq_table, 300 * 1000);
 149         if (ret) {
 150                 clk_disable_unprepare(cpu_clk);
 151                 clk_disable_unprepare(emc_clk);
 152                 return ret;
 153         }
 154
 155         policy->clk = cpu_clk;
 156         policy->suspend_freq = freq_table[0].frequency;
 157         return 0;
 158 }
 159
 160 static int tegra_cpu_exit(struct cpufreq_policy *policy)
 161 {
 162         clk_disable_unprepare(cpu_clk);
 163         clk_disable_unprepare(emc_clk);
 164         return 0;
 165 }
 166
 167 static struct cpufreq_driver tegra_cpufreq_driver = {
 168         .flags                  = CPUFREQ_NEED_INITIAL_FREQ_CHECK,
 169         .verify                 = cpufreq_generic_frequency_table_verify,
 170         .get_intermediate       = tegra_get_intermediate,
 171         .target_intermediate    = tegra_target_intermediate,
 172         .target_index           = tegra_target,
 173         .get                    = cpufreq_generic_get,
 174         .init                   = tegra_cpu_init,
 175         .exit                   = tegra_cpu_exit,
 176         .name                   = "tegra",
 177         .attr                   = cpufreq_generic_attr,
 178 #ifdef CONFIG_PM
 179         .suspend                = cpufreq_generic_suspend,
 180 #endif
 181 };
 182
 183 static int __init tegra_cpufreq_init(void)
 184 {
 185         cpu_clk = clk_get_sys(NULL, "cclk");
 186         if (IS_ERR(cpu_clk))
 187                 return PTR_ERR(cpu_clk);
 188
 189         pll_x_clk = clk_get_sys(NULL, "pll_x");
 190         if (IS_ERR(pll_x_clk))
 191                 return PTR_ERR(pll_x_clk);
 192
 193         pll_p_clk = clk_get_sys(NULL, "pll_p");
 194         if (IS_ERR(pll_p_clk))
 195                 return PTR_ERR(pll_p_clk);
 196
 197         emc_clk = clk_get_sys("cpu", "emc");
 198         if (IS_ERR(emc_clk)) {
 199                 clk_put(cpu_clk);
 200                 return PTR_ERR(emc_clk);
 201         }
 202
 203         return cpufreq_register_driver(&tegra_cpufreq_driver);
 204 }
 205
 206 static void __exit tegra_cpufreq_exit(void)
 207 {
 208         cpufreq_unregister_driver(&tegra_cpufreq_driver);
 209         clk_put(emc_clk);
 210         clk_put(cpu_clk);
 211 }
 212
 213
 214 MODULE_AUTHOR("Colin Cross <ccross@android.com>");
 215 MODULE_DESCRIPTION("cpufreq driver for Nvidia Tegra2");
 216 MODULE_LICENSE("GPL");
 217 module_init(tegra_cpufreq_init);
 218 module_exit(tegra_cpufreq_exit);