target/linux/brcm2708/patches-4.4/0581-clk-bcm-Support-rate-change-propagation-on-bcm2835-c.patch

   1 From e75f021850a698fec611538e8ff293c22a4604f5 Mon Sep 17 00:00:00 2001
   2 From: Boris Brezillon <boris.brezillon@free-electrons.com>
   3 Date: Thu, 1 Dec 2016 22:00:19 +0100
   4 Subject: [PATCH] clk: bcm: Support rate change propagation on bcm2835 clocks
   5
   6 Some peripheral clocks, like the VEC (Video EnCoder) clock need to be set
   7 to a precise rate (in our case 108MHz). With the current implementation,
   8 where peripheral clocks are not allowed to forward rate change requests
   9 to their parents, it is impossible to match this requirement unless the
  10 bootloader has configured things correctly, or a specific rate has been
  11 assigned through the DT (with the assigned-clk-rates property).
  12
  13 Add a new field to struct bcm2835_clock_data to specify which parent
  14 clocks accept rate change propagation, and support set rate propagation
  15 in bcm2835_clock_determine_rate().
  16
  17 Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
  18 Reviewed-by: Eric Anholt <eric@anholt.net>
  19 Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
  20 (cherry picked from commit 155e8b3b0ee320ae866b97dd31eba8a1f080a772)
  21 ---
  22  drivers/clk/bcm/clk-bcm2835.c | 67 ++++++++++++++++++++++++++++++++++++++++---
  23  1 file changed, 63 insertions(+), 4 deletions(-)
  24
  25 diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
  26 index 3fbd2e8..5f0e2f3 100644
  27 --- a/drivers/clk/bcm/clk-bcm2835.c
  28 +++ b/drivers/clk/bcm/clk-bcm2835.c
  29 @@ -457,6 +457,9 @@ struct bcm2835_clock_data {
  30         const char *const *parents;
  31         int num_mux_parents;
  32
  33 +       /* Bitmap encoding which parents accept rate change propagation. */
  34 +       unsigned int set_rate_parent;
  35 +
  36         u32 ctl_reg;
  37         u32 div_reg;
  38
  39 @@ -1055,10 +1058,60 @@ bcm2835_clk_is_pllc(struct clk_hw *hw)
  40         return strncmp(clk_hw_get_name(hw), "pllc", 4) == 0;
  41  }
  42
  43 +static unsigned long bcm2835_clock_choose_div_and_prate(struct clk_hw *hw,
  44 +                                                       int parent_idx,
  45 +                                                       unsigned long rate,
  46 +                                                       u32 *div,
  47 +                                                       unsigned long *prate)
  48 +{
  49 +       struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
  50 +       struct bcm2835_cprman *cprman = clock->cprman;
  51 +       const struct bcm2835_clock_data *data = clock->data;
  52 +       unsigned long best_rate;
  53 +       u32 curdiv, mindiv, maxdiv;
  54 +       struct clk_hw *parent;
  55 +
  56 +       parent = clk_hw_get_parent_by_index(hw, parent_idx);
  57 +
  58 +       if (!(BIT(parent_idx) & data->set_rate_parent)) {
  59 +               *prate = clk_hw_get_rate(parent);
  60 +               *div = bcm2835_clock_choose_div(hw, rate, *prate, true);
  61 +
  62 +               return bcm2835_clock_rate_from_divisor(clock, *prate,
  63 +                                                      *div);
  64 +       }
  65 +
  66 +       if (data->frac_bits)
  67 +               dev_warn(cprman->dev,
  68 +                       "frac bits are not used when propagating rate change");
  69 +
  70 +       /* clamp to min divider of 2 if we're dealing with a mash clock */
  71 +       mindiv = data->is_mash_clock ? 2 : 1;
  72 +       maxdiv = BIT(data->int_bits) - 1;
  73 +
  74 +       /* TODO: Be smart, and only test a subset of the available divisors. */
  75 +       for (curdiv = mindiv; curdiv <= maxdiv; curdiv++) {
  76 +               unsigned long tmp_rate;
  77 +
  78 +               tmp_rate = clk_hw_round_rate(parent, rate * curdiv);
  79 +               tmp_rate /= curdiv;
  80 +               if (curdiv == mindiv ||
  81 +                   (tmp_rate > best_rate && tmp_rate <= rate))
  82 +                       best_rate = tmp_rate;
  83 +
  84 +               if (best_rate == rate)
  85 +                       break;
  86 +       }
  87 +
  88 +       *div = curdiv << CM_DIV_FRAC_BITS;
  89 +       *prate = curdiv * best_rate;
  90 +
  91 +       return best_rate;
  92 +}
  93 +
  94  static int bcm2835_clock_determine_rate(struct clk_hw *hw,
  95                                         struct clk_rate_request *req)
  96  {
  97 -       struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
  98         struct clk_hw *parent, *best_parent = NULL;
  99         bool current_parent_is_pllc;
 100         unsigned long rate, best_rate = 0;
 101 @@ -1086,9 +1139,8 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
 102                 if (bcm2835_clk_is_pllc(parent) && !current_parent_is_pllc)
 103                         continue;
 104
 105 -               prate = clk_hw_get_rate(parent);
 106 -               div = bcm2835_clock_choose_div(hw, req->rate, prate, true);
 107 -               rate = bcm2835_clock_rate_from_divisor(clock, prate, div);
 108 +               rate = bcm2835_clock_choose_div_and_prate(hw, i, req->rate,
 109 +                                                         &div, &prate);
 110                 if (rate > best_rate && rate <= req->rate) {
 111                         best_parent = parent;
 112                         best_prate = prate;
 113 @@ -1308,6 +1360,13 @@ static struct clk *bcm2835_register_clock(struct bcm2835_cprman *cprman,
 114         if ((cprman_read(cprman, data->ctl_reg) & CM_ENABLE) == 0)
 115                 init.flags &= ~CLK_IS_CRITICAL;
 116
 117 +       /*
 118 +        * Pass the CLK_SET_RATE_PARENT flag if we are allowed to propagate
 119 +        * rate changes on at least of the parents.
 120 +        */
 121 +       if (data->set_rate_parent)
 122 +               init.flags |= CLK_SET_RATE_PARENT;
 123 +
 124         if (data->is_vpu_clock) {
 125                 init.ops = &bcm2835_vpu_clock_clk_ops;
 126         } else {
 127 --
 128 2.1.4
 129