[PATCH 00/11] clk: k210: Rewrite K210 clock without CCF

Sean Anderson seanga2 at gmail.com
Mon Apr 12 05:57:56 CEST 2021

This is something I've been meaning to do for a while but only just got around
to. The CCF has been quite unwieldy in a few ways:

* It is very rigid, and there are not easy ways to hook into it without
  rewriting many things. See e.g. things like the bypass clock and all the _half
  clocks which were created because CCF didn't support the dividers used on the
  k210. While preparing this series, I encountered several edge cases which I
  had initially overlooked (or which were not supported in the initial release).
  These would have been very difficult to fix with CCF, but were much easier to
  address be
* There is a lot of magic going on under the curtains because of all the CCF
  code which lives in many different files. Some things live in drivers, but
  many things live in e.g. clk-uclass.c. So many things live in so many files
  and it can be very difficult to get a handle on what exactly happens.
  Complicating this is that there is a conflation of struct clk as a handle and
  struct clk as a device. In this regard, refcounting is completely broken. IMO
  we should just do away with refcounts and only disable clocks when explicitly
  asked for.
* It is very dependent on runtime initialization. Typically, everything is
  initialized by calling into various register() functions, usually with several
  wrappers to avoid specifying all the arguments. This balloons the runtime
  memory usage since there are so many devices created. It also makes it hard to
  debug, since if you do it the "typical" way it is easy to accidentally assign
  a clock to the wrong register.
* It inflates code size by pulling in not just some dead code (e.g. this driver
  does not use divider tables but they are in clk-divider anyway) but also
  pulling in numerous imx-specific clocks. This could be fixed, but I don't want
  to due to the other reasons listed.

I am very happy to have completely excised it from my driver. IMO there should
be big warning signs on the CCF warning not to use it for new code. This would
hopefully dissuade those like myself who had no idea that CCF was *not* in fact
a good way to write a clock driver.

Overall there is a total savings of 12k from this series. Before:
   text	   data	    bss	    dec	    hex	filename
 292485	  32672	  12624	 337781	  52775	u-boot
   text	   data	    bss	    dec	    hex	filename
 283125	  29856	  12624	 325605	  4f7e5	u-boot

This series depends on

Sean Anderson (11):
  clk: Allow force setting clock defaults before relocation
  clk: k210: Rewrite to remove CCF
  clk: k210: Move pll into the rest of the driver
  clk: k210: Implement soc_clk_dump
  clk: k210: Re-add support for setting rate
  clk: k210: Don't set PLL rates if we are already at the correct rate
  clk: k210: Remove bypass driver
  clk: k210: Move k210 clock out of its own subdirectory
  k210: dts: Set PLL1 to the same rate as PLL0
  k210: Don't imply CCF
  test: Add K210 PLL tests to sandbox defconfigs

 MAINTAINERS                             |    4 +-
 arch/riscv/dts/k210.dtsi                |    2 +
 board/sipeed/maix/Kconfig               |    2 -
 configs/sandbox64_defconfig             |    2 +
 configs/sandbox_defconfig               |    2 +
 configs/sandbox_flattree_defconfig      |    2 +
 configs/sipeed_maix_bitm_defconfig      |    1 -
 drivers/clk/Kconfig                     |   14 +-
 drivers/clk/Makefile                    |    2 +-
 drivers/clk/clk-uclass.c                |    9 +-
 drivers/clk/clk_kendryte.c              | 1319 +++++++++++++++++++++++
 drivers/clk/kendryte/Kconfig            |   12 -
 drivers/clk/kendryte/Makefile           |    1 -
 drivers/clk/kendryte/bypass.c           |  273 -----
 drivers/clk/kendryte/clk.c              |  668 ------------
 drivers/clk/kendryte/pll.c              |  585 ----------
 include/clk.h                           |    4 +-
 include/dt-bindings/clock/k210-sysctl.h |   94 +-
 include/kendryte/bypass.h               |   31 -
 include/kendryte/clk.h                  |   35 -
 include/kendryte/pll.h                  |   34 -
 21 files changed, 1399 insertions(+), 1697 deletions(-)
 create mode 100644 drivers/clk/clk_kendryte.c
 delete mode 100644 drivers/clk/kendryte/Kconfig
 delete mode 100644 drivers/clk/kendryte/Makefile
 delete mode 100644 drivers/clk/kendryte/bypass.c
 delete mode 100644 drivers/clk/kendryte/clk.c
 delete mode 100644 drivers/clk/kendryte/pll.c
 delete mode 100644 include/kendryte/bypass.h
 delete mode 100644 include/kendryte/clk.h


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