[PATCH RFC 0/3] clk: support arbitrary clk_register() sequence

[Yang Xiwen]

On 10/15/2025 6:03 AM, Tom Rini wrote:
> On Sat, Jun 21, 2025 at 06:54:17PM +0800, Yang Xiwen wrote:
>
>> Currently U-Boot clk framework mandates the sequence of registering clks
>> to begin from root, and then its children. This is an addtional
>> requirement that doesn't exist in Linux kernel, which makes clk driver
>> porting more difficult.
>>
>> Let's handle this entirely in clk framework and give driver the freedom
>> to register clocks in any order.
>>
>> This is done by assigning the parent "lazily". It will cache the parent
>> name in the core clk struct and try to refresh it when clk consumers
>> call clk_get_parent(). It's transparent to clk consumers as long as they
>> only use APIs provided by clk framework.
>>
>> I've ran `ut dm clk*` and verified these commits does not break any
>> existing testcases. Though no new testcase is added because I think
>> existing testcases already test the logic very well.
> Sorry for the very late review. When I build this on say
> rock-4c-plus-rk3399 this is the size growth I see:
>              rock-4c-plus-rk3399: all +228 spl/u-boot-spl:all +500 spl/u-boot-spl:text +500 text +228 tpl/u-boot-tpl:all +552 tpl/u-boot-tpl:text +552
>                 u-boot: add: 1/0, grow: 1/0 bytes: 228/0 (228)
>                   function                                   old     new   delta
>                   device_reparent                              -     120    +120
>                   clk_get_parent                              56     164    +108
>                 spl-u-boot-spl: add: 4/0, grow: 1/0 bytes: 500/0 (500)
>                   function                                   old     new   delta
>                   uclass_find_device_by_namelen                -     172    +172
>                   device_reparent                              -     120    +120
>                   clk_get_parent                              56     144     +88
>                   uclass_find_device_by_name                   -      68     +68
>                   uclass_get_device_by_name                    -      52     +52
>                 tpl-u-boot-tpl: add: 5/0, grow: 1/0 bytes: 552/0 (552)
>                   function                                   old     new   delta
>                   uclass_find_device_by_namelen                -     172    +172
>                   device_reparent                              -     120    +120
>                   clk_get_parent                              56     144     +88
>                   uclass_find_device_by_name                   -      68     +68
>                   uclass_get_device_by_name                    -      52     +52
>                   strncmp                                      -      52     +52
>
> (using buildman's 'bloat' features to report size change). I'm fine with
> the growth in U-Boot itself, but that's just too much in SPL and TPL and
> we need to figure out if we can avoid that somehow.
>
I'll make this feature optional for  SPL/TPL, but would still like it to 
be always enabled for U-Boot itself.

-- 
Regards,
Yang Xiwen