drivers/clk/rockchip/clk-mmc-phase.c

   1 /*
   2  * Copyright 2014 Google, Inc
   3  * Author: Alexandru M Stan <amstan@chromium.org>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  */
  15
  16 #include <linux/slab.h>
  17 #include <linux/clk.h>
  18 #include <linux/clk-provider.h>
  19 #include <linux/io.h>
  20 #include <linux/kernel.h>
  21 #include "clk.h"
  22
  23 struct rockchip_mmc_clock {
  24         struct clk_hw   hw;
  25         void __iomem    *reg;
  26         int             id;
  27         int             shift;
  28 };
  29
  30 #define to_mmc_clock(_hw) container_of(_hw, struct rockchip_mmc_clock, hw)
  31
  32 #define RK3288_MMC_CLKGEN_DIV 2
  33
  34 static unsigned long rockchip_mmc_recalc(struct clk_hw *hw,
  35                                          unsigned long parent_rate)
  36 {
  37         return parent_rate / RK3288_MMC_CLKGEN_DIV;
  38 }
  39
  40 #define ROCKCHIP_MMC_DELAY_SEL BIT(10)
  41 #define ROCKCHIP_MMC_DEGREE_MASK 0x3
  42 #define ROCKCHIP_MMC_DELAYNUM_OFFSET 2
  43 #define ROCKCHIP_MMC_DELAYNUM_MASK (0xff << ROCKCHIP_MMC_DELAYNUM_OFFSET)
  44
  45 #define PSECS_PER_SEC 1000000000000LL
  46
  47 /*
  48  * Each fine delay is between 44ps-77ps. Assume each fine delay is 60ps to
  49  * simplify calculations. So 45degs could be anywhere between 33deg and 57.8deg.
  50  */
  51 #define ROCKCHIP_MMC_DELAY_ELEMENT_PSEC 60
  52
  53 static int rockchip_mmc_get_phase(struct clk_hw *hw)
  54 {
  55         struct rockchip_mmc_clock *mmc_clock = to_mmc_clock(hw);
  56         unsigned long rate = clk_get_rate(hw->clk);
  57         u32 raw_value;
  58         u16 degrees;
  59         u32 delay_num = 0;
  60
  61         raw_value = readl(mmc_clock->reg) >> (mmc_clock->shift);
  62
  63         degrees = (raw_value & ROCKCHIP_MMC_DEGREE_MASK) * 90;
  64
  65         if (raw_value & ROCKCHIP_MMC_DELAY_SEL) {
  66                 /* degrees/delaynum * 10000 */
  67                 unsigned long factor = (ROCKCHIP_MMC_DELAY_ELEMENT_PSEC / 10) *
  68                                         36 * (rate / 1000000);
  69
  70                 delay_num = (raw_value & ROCKCHIP_MMC_DELAYNUM_MASK);
  71                 delay_num >>= ROCKCHIP_MMC_DELAYNUM_OFFSET;
  72                 degrees += DIV_ROUND_CLOSEST(delay_num * factor, 10000);
  73         }
  74
  75         return degrees % 360;
  76 }
  77
  78 static int rockchip_mmc_set_phase(struct clk_hw *hw, int degrees)
  79 {
  80         struct rockchip_mmc_clock *mmc_clock = to_mmc_clock(hw);
  81         unsigned long rate = clk_get_rate(hw->clk);
  82         u8 nineties, remainder;
  83         u8 delay_num;
  84         u32 raw_value;
  85         u32 delay;
  86
  87         nineties = degrees / 90;
  88         remainder = (degrees % 90);
  89
  90         /*
  91          * Due to the inexact nature of the "fine" delay, we might
  92          * actually go non-monotonic.  We don't go _too_ monotonic
  93          * though, so we should be OK.  Here are options of how we may
  94          * work:
  95          *
  96          * Ideally we end up with:
  97          *   1.0, 2.0, ..., 69.0, 70.0, ...,  89.0, 90.0
  98          *
  99          * On one extreme (if delay is actually 44ps):
 100          *   .73, 1.5, ..., 50.6, 51.3, ...,  65.3, 90.0
 101          * The other (if delay is actually 77ps):
 102          *   1.3, 2.6, ..., 88.6. 89.8, ..., 114.0, 90
 103          *
 104          * It's possible we might make a delay that is up to 25
 105          * degrees off from what we think we're making.  That's OK
 106          * though because we should be REALLY far from any bad range.
 107          */
 108
 109         /*
 110          * Convert to delay; do a little extra work to make sure we
 111          * don't overflow 32-bit / 64-bit numbers.
 112          */
 113         delay = 10000000; /* PSECS_PER_SEC / 10000 / 10 */
 114         delay *= remainder;
 115         delay = DIV_ROUND_CLOSEST(delay,
 116                         (rate / 1000) * 36 *
 117                                 (ROCKCHIP_MMC_DELAY_ELEMENT_PSEC / 10));
 118
 119         delay_num = (u8) min_t(u32, delay, 255);
 120
 121         raw_value = delay_num ? ROCKCHIP_MMC_DELAY_SEL : 0;
 122         raw_value |= delay_num << ROCKCHIP_MMC_DELAYNUM_OFFSET;
 123         raw_value |= nineties;
 124         writel(HIWORD_UPDATE(raw_value, 0x07ff, mmc_clock->shift),
 125                mmc_clock->reg);
 126
 127         pr_debug("%s->set_phase(%d) delay_nums=%u reg[0x%p]=0x%03x actual_degrees=%d\n",
 128                 clk_hw_get_name(hw), degrees, delay_num,
 129                 mmc_clock->reg, raw_value>>(mmc_clock->shift),
 130                 rockchip_mmc_get_phase(hw)
 131         );
 132
 133         return 0;
 134 }
 135
 136 static const struct clk_ops rockchip_mmc_clk_ops = {
 137         .recalc_rate    = rockchip_mmc_recalc,
 138         .get_phase      = rockchip_mmc_get_phase,
 139         .set_phase      = rockchip_mmc_set_phase,
 140 };
 141
 142 struct clk *rockchip_clk_register_mmc(const char *name,
 143                                 const char *const *parent_names, u8 num_parents,
 144                                 void __iomem *reg, int shift)
 145 {
 146         struct clk_init_data init;
 147         struct rockchip_mmc_clock *mmc_clock;
 148         struct clk *clk;
 149
 150         mmc_clock = kmalloc(sizeof(*mmc_clock), GFP_KERNEL);
 151         if (!mmc_clock)
 152                 return ERR_PTR(-ENOMEM);
 153
 154         init.name = name;
 155         init.flags = 0;
 156         init.num_parents = num_parents;
 157         init.parent_names = parent_names;
 158         init.ops = &rockchip_mmc_clk_ops;
 159
 160         mmc_clock->hw.init = &init;
 161         mmc_clock->reg = reg;
 162         mmc_clock->shift = shift;
 163
 164         clk = clk_register(NULL, &mmc_clock->hw);
 165         if (IS_ERR(clk))
 166                 kfree(mmc_clock);
 167
 168         return clk;
 169 }