[PATCH v2 00/11] clk: k210: Rewrite K210 clock without CCF

[Damien Le Moal]

On 2021/06/04 12:58, Sean Anderson wrote:
> 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 because each funcion is implemented in one place.
> * 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.
>    text	   data	    bss	    dec	    hex	filename
>  292485	  32672	  12624	 337781	  52775	before/u-boot
>  283125	  29856	  12624	 325605	  4f7e5	after/u-boot
> 
> This series depends on
> https://patchwork.ozlabs.org/project/uboot/list/?series=238211
> 
> Changes in v2:
> - Convert stage to enum
> - Only force probe clocks pre-reloc
> - Rebase on u-boot/master
> 
> 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                |   27 +-
>  drivers/clk/clk_kendryte.c              | 1320 +++++++++++++++++++++++
>  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 ----------
>  drivers/clk/rockchip/clk_rk3308.c       |    2 +-
>  drivers/core/device.c                   |    2 +-
>  drivers/net/gmac_rockchip.c             |    2 +-
>  include/clk.h                           |   30 +-
>  include/dt-bindings/clock/k210-sysctl.h |   94 +-
>  include/kendryte/bypass.h               |   31 -
>  include/kendryte/clk.h                  |   35 -
>  include/kendryte/pll.h                  |   34 -
>  24 files changed, 1436 insertions(+), 1711 deletions(-)

Awesome cleanup !

I will try to revisit the clock rate setting in Linux and re-check where we diverge.

FYI: I have a draft series adding K210 builds to buildroot here:

https://github.com/damien-lemoal/buildroot (k210-v2 branch)

I cannot get userspace to run with kernel 5.12, even adding the binfmt_flat
change in 5.13 (commit 04d82a6d0881 "binfmt_flat: allow not offsetting data
start"). Not sure what is going on yet. 5.13-rc4 kernel works perfectly.


>  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
> 


-- 
Damien Le Moal
Western Digital Research