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

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright 2014 Google, Inc
   4  * Author: Alexandru M Stan <amstan@chromium.org>
   5  */
   6
   7 #include <linux/slab.h>
   8 #include <linux/clk.h>
   9 #include <linux/clk-provider.h>
  10 #include <linux/io.h>
  11 #include <linux/kernel.h>
  12 #include "clk.h"
  13
  14 struct rockchip_mmc_clock {
  15         struct clk_hw   hw;
  16         void __iomem    *reg;
  17         int             id;
  18         int             shift;
  19         int             cached_phase;
  20         struct notifier_block clk_rate_change_nb;
  21 };
  22
  23 #define to_mmc_clock(_hw) container_of(_hw, struct rockchip_mmc_clock, hw)
  24
  25 #define RK3288_MMC_CLKGEN_DIV 2
  26
  27 static unsigned long rockchip_mmc_recalc(struct clk_hw *hw,
  28                                          unsigned long parent_rate)
  29 {
  30         return parent_rate / RK3288_MMC_CLKGEN_DIV;
  31 }
  32
  33 #define ROCKCHIP_MMC_DELAY_SEL BIT(10)
  34 #define ROCKCHIP_MMC_DEGREE_MASK 0x3
  35 #define ROCKCHIP_MMC_DELAYNUM_OFFSET 2
  36 #define ROCKCHIP_MMC_DELAYNUM_MASK (0xff << ROCKCHIP_MMC_DELAYNUM_OFFSET)
  37
  38 #define PSECS_PER_SEC 1000000000000LL
  39
  40 /*
  41  * Each fine delay is between 44ps-77ps. Assume each fine delay is 60ps to
  42  * simplify calculations. So 45degs could be anywhere between 33deg and 57.8deg.
  43  */
  44 #define ROCKCHIP_MMC_DELAY_ELEMENT_PSEC 60
  45
  46 static int rockchip_mmc_get_phase(struct clk_hw *hw)
  47 {
  48         struct rockchip_mmc_clock *mmc_clock = to_mmc_clock(hw);
  49         unsigned long rate = clk_hw_get_rate(hw);
  50         u32 raw_value;
  51         u16 degrees;
  52         u32 delay_num = 0;
  53
  54         /* Constant signal, no measurable phase shift */
  55         if (!rate)
  56                 return 0;
  57
  58         raw_value = readl(mmc_clock->reg) >> (mmc_clock->shift);
  59
  60         degrees = (raw_value & ROCKCHIP_MMC_DEGREE_MASK) * 90;
  61
  62         if (raw_value & ROCKCHIP_MMC_DELAY_SEL) {
  63                 /* degrees/delaynum * 1000000 */
  64                 unsigned long factor = (ROCKCHIP_MMC_DELAY_ELEMENT_PSEC / 10) *
  65                                         36 * (rate / 10000);
  66
  67                 delay_num = (raw_value & ROCKCHIP_MMC_DELAYNUM_MASK);
  68                 delay_num >>= ROCKCHIP_MMC_DELAYNUM_OFFSET;
  69                 degrees += DIV_ROUND_CLOSEST(delay_num * factor, 1000000);
  70         }
  71
  72         return degrees % 360;
  73 }
  74
  75 static int rockchip_mmc_set_phase(struct clk_hw *hw, int degrees)
  76 {
  77         struct rockchip_mmc_clock *mmc_clock = to_mmc_clock(hw);
  78         unsigned long rate = clk_hw_get_rate(hw);
  79         u8 nineties, remainder;
  80         u8 delay_num;
  81         u32 raw_value;
  82         u32 delay;
  83
  84         /*
  85          * The below calculation is based on the output clock from
  86          * MMC host to the card, which expects the phase clock inherits
  87          * the clock rate from its parent, namely the output clock
  88          * provider of MMC host. However, things may go wrong if
  89          * (1) It is orphan.
  90          * (2) It is assigned to the wrong parent.
  91          *
  92          * This check help debug the case (1), which seems to be the
  93          * most likely problem we often face and which makes it difficult
  94          * for people to debug unstable mmc tuning results.
  95          */
  96         if (!rate) {
  97                 pr_err("%s: invalid clk rate\n", __func__);
  98                 return -EINVAL;
  99         }
 100
 101         nineties = degrees / 90;
 102         remainder = (degrees % 90);
 103
 104         /*
 105          * Due to the inexact nature of the "fine" delay, we might
 106          * actually go non-monotonic.  We don't go _too_ monotonic
 107          * though, so we should be OK.  Here are options of how we may
 108          * work:
 109          *
 110          * Ideally we end up with:
 111          *   1.0, 2.0, ..., 69.0, 70.0, ...,  89.0, 90.0
 112          *
 113          * On one extreme (if delay is actually 44ps):
 114          *   .73, 1.5, ..., 50.6, 51.3, ...,  65.3, 90.0
 115          * The other (if delay is actually 77ps):
 116          *   1.3, 2.6, ..., 88.6. 89.8, ..., 114.0, 90
 117          *
 118          * It's possible we might make a delay that is up to 25
 119          * degrees off from what we think we're making.  That's OK
 120          * though because we should be REALLY far from any bad range.
 121          */
 122
 123         /*
 124          * Convert to delay; do a little extra work to make sure we
 125          * don't overflow 32-bit / 64-bit numbers.
 126          */
 127         delay = 10000000; /* PSECS_PER_SEC / 10000 / 10 */
 128         delay *= remainder;
 129         delay = DIV_ROUND_CLOSEST(delay,
 130                         (rate / 1000) * 36 *
 131                                 (ROCKCHIP_MMC_DELAY_ELEMENT_PSEC / 10));
 132
 133         delay_num = (u8) min_t(u32, delay, 255);
 134
 135         raw_value = delay_num ? ROCKCHIP_MMC_DELAY_SEL : 0;
 136         raw_value |= delay_num << ROCKCHIP_MMC_DELAYNUM_OFFSET;
 137         raw_value |= nineties;
 138         writel(HIWORD_UPDATE(raw_value, 0x07ff, mmc_clock->shift),
 139                mmc_clock->reg);
 140
 141         pr_debug("%s->set_phase(%d) delay_nums=%u reg[0x%p]=0x%03x actual_degrees=%d\n",
 142                 clk_hw_get_name(hw), degrees, delay_num,
 143                 mmc_clock->reg, raw_value>>(mmc_clock->shift),
 144                 rockchip_mmc_get_phase(hw)
 145         );
 146
 147         return 0;
 148 }
 149
 150 static const struct clk_ops rockchip_mmc_clk_ops = {
 151         .recalc_rate    = rockchip_mmc_recalc,
 152         .get_phase      = rockchip_mmc_get_phase,
 153         .set_phase      = rockchip_mmc_set_phase,
 154 };
 155
 156 #define to_rockchip_mmc_clock(x) \
 157         container_of(x, struct rockchip_mmc_clock, clk_rate_change_nb)
 158 static int rockchip_mmc_clk_rate_notify(struct notifier_block *nb,
 159                                         unsigned long event, void *data)
 160 {
 161         struct rockchip_mmc_clock *mmc_clock = to_rockchip_mmc_clock(nb);
 162         struct clk_notifier_data *ndata = data;
 163
 164         /*
 165          * rockchip_mmc_clk is mostly used by mmc controllers to sample
 166          * the intput data, which expects the fixed phase after the tuning
 167          * process. However if the clock rate is changed, the phase is stale
 168          * and may break the data sampling. So here we try to restore the phase
 169          * for that case, except that
 170          * (1) cached_phase is invaild since we inevitably cached it when the
 171          * clock provider be reparented from orphan to its real parent in the
 172          * first place. Otherwise we may mess up the initialization of MMC cards
 173          * since we only set the default sample phase and drive phase later on.
 174          * (2) the new coming rate is higher than the older one since mmc driver
 175          * set the max-frequency to match the boards' ability but we can't go
 176          * over the heads of that, otherwise the tests smoke out the issue.
 177          */
 178         if (ndata->old_rate <= ndata->new_rate)
 179                 return NOTIFY_DONE;
 180
 181         if (event == PRE_RATE_CHANGE)
 182                 mmc_clock->cached_phase =
 183                         rockchip_mmc_get_phase(&mmc_clock->hw);
 184         else if (mmc_clock->cached_phase != -EINVAL &&
 185                  event == POST_RATE_CHANGE)
 186                 rockchip_mmc_set_phase(&mmc_clock->hw, mmc_clock->cached_phase);
 187
 188         return NOTIFY_DONE;
 189 }
 190
 191 struct clk *rockchip_clk_register_mmc(const char *name,
 192                                 const char *const *parent_names, u8 num_parents,
 193                                 void __iomem *reg, int shift)
 194 {
 195         struct clk_init_data init;
 196         struct rockchip_mmc_clock *mmc_clock;
 197         struct clk *clk;
 198         int ret;
 199
 200         mmc_clock = kmalloc(sizeof(*mmc_clock), GFP_KERNEL);
 201         if (!mmc_clock)
 202                 return ERR_PTR(-ENOMEM);
 203
 204         init.name = name;
 205         init.flags = 0;
 206         init.num_parents = num_parents;
 207         init.parent_names = parent_names;
 208         init.ops = &rockchip_mmc_clk_ops;
 209
 210         mmc_clock->hw.init = &init;
 211         mmc_clock->reg = reg;
 212         mmc_clock->shift = shift;
 213
 214         clk = clk_register(NULL, &mmc_clock->hw);
 215         if (IS_ERR(clk)) {
 216                 ret = PTR_ERR(clk);
 217                 goto err_register;
 218         }
 219
 220         mmc_clock->clk_rate_change_nb.notifier_call =
 221                                 &rockchip_mmc_clk_rate_notify;
 222         ret = clk_notifier_register(clk, &mmc_clock->clk_rate_change_nb);
 223         if (ret)
 224                 goto err_notifier;
 225
 226         return clk;
 227 err_notifier:
 228         clk_unregister(clk);
 229 err_register:
 230         kfree(mmc_clock);
 231         return ERR_PTR(ret);
 232 }