drivers/clk/sunxi-ng/ccu_phase.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2016 Maxime Ripard
   4  * Maxime Ripard <maxime.ripard@free-electrons.com>
   5  */
   6
   7 #include <linux/clk-provider.h>
   8 #include <linux/io.h>
   9 #include <linux/spinlock.h>
  10
  11 #include "ccu_phase.h"
  12
  13 static int ccu_phase_get_phase(struct clk_hw *hw)
  14 {
  15         struct ccu_phase *phase = hw_to_ccu_phase(hw);
  16         struct clk_hw *parent, *grandparent;
  17         unsigned int parent_rate, grandparent_rate;
  18         u16 step, parent_div;
  19         u32 reg;
  20         u8 delay;
  21
  22         reg = readl(phase->common.base + phase->common.reg);
  23         delay = (reg >> phase->shift);
  24         delay &= (1 << phase->width) - 1;
  25
  26         if (!delay)
  27                 return 180;
  28
  29         /* Get our parent clock, it's the one that can adjust its rate */
  30         parent = clk_hw_get_parent(hw);
  31         if (!parent)
  32                 return -EINVAL;
  33
  34         /* And its rate */
  35         parent_rate = clk_hw_get_rate(parent);
  36         if (!parent_rate)
  37                 return -EINVAL;
  38
  39         /* Now, get our parent's parent (most likely some PLL) */
  40         grandparent = clk_hw_get_parent(parent);
  41         if (!grandparent)
  42                 return -EINVAL;
  43
  44         /* And its rate */
  45         grandparent_rate = clk_hw_get_rate(grandparent);
  46         if (!grandparent_rate)
  47                 return -EINVAL;
  48
  49         /* Get our parent clock divider */
  50         parent_div = grandparent_rate / parent_rate;
  51
  52         step = DIV_ROUND_CLOSEST(360, parent_div);
  53         return delay * step;
  54 }
  55
  56 static int ccu_phase_set_phase(struct clk_hw *hw, int degrees)
  57 {
  58         struct ccu_phase *phase = hw_to_ccu_phase(hw);
  59         struct clk_hw *parent, *grandparent;
  60         unsigned int parent_rate, grandparent_rate;
  61         unsigned long flags;
  62         u32 reg;
  63         u8 delay;
  64
  65         /* Get our parent clock, it's the one that can adjust its rate */
  66         parent = clk_hw_get_parent(hw);
  67         if (!parent)
  68                 return -EINVAL;
  69
  70         /* And its rate */
  71         parent_rate = clk_hw_get_rate(parent);
  72         if (!parent_rate)
  73                 return -EINVAL;
  74
  75         /* Now, get our parent's parent (most likely some PLL) */
  76         grandparent = clk_hw_get_parent(parent);
  77         if (!grandparent)
  78                 return -EINVAL;
  79
  80         /* And its rate */
  81         grandparent_rate = clk_hw_get_rate(grandparent);
  82         if (!grandparent_rate)
  83                 return -EINVAL;
  84
  85         if (degrees != 180) {
  86                 u16 step, parent_div;
  87
  88                 /* Get our parent divider */
  89                 parent_div = grandparent_rate / parent_rate;
  90
  91                 /*
  92                  * We can only outphase the clocks by multiple of the
  93                  * PLL's period.
  94                  *
  95                  * Since our parent clock is only a divider, and the
  96                  * formula to get the outphasing in degrees is deg =
  97                  * 360 * delta / period
  98                  *
  99                  * If we simplify this formula, we can see that the
 100                  * only thing that we're concerned about is the number
 101                  * of period we want to outphase our clock from, and
 102                  * the divider set by our parent clock.
 103                  */
 104                 step = DIV_ROUND_CLOSEST(360, parent_div);
 105                 delay = DIV_ROUND_CLOSEST(degrees, step);
 106         } else {
 107                 delay = 0;
 108         }
 109
 110         spin_lock_irqsave(phase->common.lock, flags);
 111         reg = readl(phase->common.base + phase->common.reg);
 112         reg &= ~GENMASK(phase->width + phase->shift - 1, phase->shift);
 113         writel(reg | (delay << phase->shift),
 114                phase->common.base + phase->common.reg);
 115         spin_unlock_irqrestore(phase->common.lock, flags);
 116
 117         return 0;
 118 }
 119
 120 const struct clk_ops ccu_phase_ops = {
 121         .get_phase      = ccu_phase_get_phase,
 122         .set_phase      = ccu_phase_set_phase,
 123 };