drivers/clk/sunxi-ng/ccu_sdm.c

   1 /*
   2  * Copyright (C) 2017 Chen-Yu Tsai <wens@csie.org>
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of
   7  * the License, or (at your option) any later version.
   8  */
   9
  10 #include <linux/clk-provider.h>
  11 #include <linux/spinlock.h>
  12
  13 #include "ccu_sdm.h"
  14
  15 bool ccu_sdm_helper_is_enabled(struct ccu_common *common,
  16                                struct ccu_sdm_internal *sdm)
  17 {
  18         if (!(common->features & CCU_FEATURE_SIGMA_DELTA_MOD))
  19                 return false;
  20
  21         if (sdm->enable && !(readl(common->base + common->reg) & sdm->enable))
  22                 return false;
  23
  24         return !!(readl(common->base + sdm->tuning_reg) & sdm->tuning_enable);
  25 }
  26
  27 void ccu_sdm_helper_enable(struct ccu_common *common,
  28                            struct ccu_sdm_internal *sdm,
  29                            unsigned long rate)
  30 {
  31         unsigned long flags;
  32         unsigned int i;
  33         u32 reg;
  34
  35         if (!(common->features & CCU_FEATURE_SIGMA_DELTA_MOD))
  36                 return;
  37
  38         /* Set the pattern */
  39         for (i = 0; i < sdm->table_size; i++)
  40                 if (sdm->table[i].rate == rate)
  41                         writel(sdm->table[i].pattern,
  42                                common->base + sdm->tuning_reg);
  43
  44         /* Make sure SDM is enabled */
  45         spin_lock_irqsave(common->lock, flags);
  46         reg = readl(common->base + sdm->tuning_reg);
  47         writel(reg | sdm->tuning_enable, common->base + sdm->tuning_reg);
  48         spin_unlock_irqrestore(common->lock, flags);
  49
  50         spin_lock_irqsave(common->lock, flags);
  51         reg = readl(common->base + common->reg);
  52         writel(reg | sdm->enable, common->base + common->reg);
  53         spin_unlock_irqrestore(common->lock, flags);
  54 }
  55
  56 void ccu_sdm_helper_disable(struct ccu_common *common,
  57                             struct ccu_sdm_internal *sdm)
  58 {
  59         unsigned long flags;
  60         u32 reg;
  61
  62         if (!(common->features & CCU_FEATURE_SIGMA_DELTA_MOD))
  63                 return;
  64
  65         spin_lock_irqsave(common->lock, flags);
  66         reg = readl(common->base + common->reg);
  67         writel(reg & ~sdm->enable, common->base + common->reg);
  68         spin_unlock_irqrestore(common->lock, flags);
  69
  70         spin_lock_irqsave(common->lock, flags);
  71         reg = readl(common->base + sdm->tuning_reg);
  72         writel(reg & ~sdm->tuning_enable, common->base + sdm->tuning_reg);
  73         spin_unlock_irqrestore(common->lock, flags);
  74 }
  75
  76 /*
  77  * Sigma delta modulation provides a way to do fractional-N frequency
  78  * synthesis, in essence allowing the PLL to output any frequency
  79  * within its operational range. On earlier SoCs such as the A10/A20,
  80  * some PLLs support this. On later SoCs, all PLLs support this.
  81  *
  82  * The datasheets do not explain what the "wave top" and "wave bottom"
  83  * parameters mean or do, nor how to calculate the effective output
  84  * frequency. The only examples (and real world usage) are for the audio
  85  * PLL to generate 24.576 and 22.5792 MHz clock rates used by the audio
  86  * peripherals. The author lacks the underlying domain knowledge to
  87  * pursue this.
  88  *
  89  * The goal and function of the following code is to support the two
  90  * clock rates used by the audio subsystem, allowing for proper audio
  91  * playback and capture without any pitch or speed changes.
  92  */
  93 bool ccu_sdm_helper_has_rate(struct ccu_common *common,
  94                              struct ccu_sdm_internal *sdm,
  95                              unsigned long rate)
  96 {
  97         unsigned int i;
  98
  99         if (!(common->features & CCU_FEATURE_SIGMA_DELTA_MOD))
 100                 return false;
 101
 102         for (i = 0; i < sdm->table_size; i++)
 103                 if (sdm->table[i].rate == rate)
 104                         return true;
 105
 106         return false;
 107 }
 108
 109 unsigned long ccu_sdm_helper_read_rate(struct ccu_common *common,
 110                                        struct ccu_sdm_internal *sdm,
 111                                        u32 m, u32 n)
 112 {
 113         unsigned int i;
 114         u32 reg;
 115
 116         pr_debug("%s: Read sigma-delta modulation setting\n",
 117                  clk_hw_get_name(&common->hw));
 118
 119         if (!(common->features & CCU_FEATURE_SIGMA_DELTA_MOD))
 120                 return 0;
 121
 122         pr_debug("%s: clock is sigma-delta modulated\n",
 123                  clk_hw_get_name(&common->hw));
 124
 125         reg = readl(common->base + sdm->tuning_reg);
 126
 127         pr_debug("%s: pattern reg is 0x%x",
 128                  clk_hw_get_name(&common->hw), reg);
 129
 130         for (i = 0; i < sdm->table_size; i++)
 131                 if (sdm->table[i].pattern == reg &&
 132                     sdm->table[i].m == m && sdm->table[i].n == n)
 133                         return sdm->table[i].rate;
 134
 135         /* We can't calculate the effective clock rate, so just fail. */
 136         return 0;
 137 }
 138
 139 int ccu_sdm_helper_get_factors(struct ccu_common *common,
 140                                struct ccu_sdm_internal *sdm,
 141                                unsigned long rate,
 142                                unsigned long *m, unsigned long *n)
 143 {
 144         unsigned int i;
 145
 146         if (!(common->features & CCU_FEATURE_SIGMA_DELTA_MOD))
 147                 return -EINVAL;
 148
 149         for (i = 0; i < sdm->table_size; i++)
 150                 if (sdm->table[i].rate == rate) {
 151                         *m = sdm->table[i].m;
 152                         *n = sdm->table[i].n;
 153                         return 0;
 154                 }
 155
 156         /* nothing found */
 157         return -EINVAL;
 158 }