git.openwrt.org Git - openwrt/staging/ldir.git/blob

   1 From a1dcaba80910c0196b6e51111ba3890372067e0e Mon Sep 17 00:00:00 2001
   2 From: Eric Anholt <eric@anholt.net>
   3 Date: Thu, 2 May 2019 15:11:05 -0700
   4 Subject: [PATCH] clk: bcm2835: Add support for setting leaf clock
   5  rates while running.
   6
   7 As long as you wait for !BUSY, you can do glitch-free updates of clock
   8 rate while the clock is running.
   9
  10 Signed-off-by: Eric Anholt <eric@anholt.net>
  11 ---
  12  drivers/clk/bcm/clk-bcm2835.c | 22 +++++++++++++---------
  13  1 file changed, 13 insertions(+), 9 deletions(-)
  14
  15 --- a/drivers/clk/bcm/clk-bcm2835.c
  16 +++ b/drivers/clk/bcm/clk-bcm2835.c
  17 @@ -1110,15 +1110,19 @@ static int bcm2835_clock_set_rate(struct
  18
  19         spin_lock(&cprman->regs_lock);
  20
  21 -       /*
  22 -        * Setting up frac support
  23 -        *
  24 -        * In principle it is recommended to stop/start the clock first,
  25 -        * but as we set CLK_SET_RATE_GATE during registration of the
  26 -        * clock this requirement should be take care of by the
  27 -        * clk-framework.
  28 +       ctl = cprman_read(cprman, data->ctl_reg);
  29 +
  30 +       /* If the clock is running, we have to pause clock generation while
  31 +        * updating the control and div regs.  This is glitchless (no clock
  32 +        * signals generated faster than the rate) but each reg access is two
  33 +        * OSC cycles so the clock will slow down for a moment.
  34          */
  35 -       ctl = cprman_read(cprman, data->ctl_reg) & ~CM_FRAC;
  36 +       if (ctl & CM_ENABLE) {
  37 +               cprman_write(cprman, data->ctl_reg, ctl & ~CM_ENABLE);
  38 +               bcm2835_clock_wait_busy(clock);
  39 +       }
  40 +
  41 +       ctl &= ~CM_FRAC;
  42         ctl |= (div & CM_DIV_FRAC_MASK) ? CM_FRAC : 0;
  43         cprman_write(cprman, data->ctl_reg, ctl);
  44
  45 @@ -1494,7 +1498,7 @@ static struct clk_hw *bcm2835_register_c
  46                 init.ops = &bcm2835_vpu_clock_clk_ops;
  47         } else {
  48                 init.ops = &bcm2835_clock_clk_ops;
  49 -               init.flags |= CLK_SET_RATE_GATE | CLK_SET_PARENT_GATE;
  50 +               init.flags |= CLK_SET_PARENT_GATE;
  51
  52                 /* If the clock wasn't actually enabled at boot, it's not
  53                  * critical.