Re: [PATCH RFC v4 01/12] dt-bindings: clk: zte: Add zx297520v3 top clock and reset bindings

[Stefan Dösinger]

Hi Conor,
Am Donnerstag, 18. Juni 2026, 22:54:53 Ostafrikanische Zeit schrieb Conor 
Dooley:

I think I get the gist of your suggestions. I have a few follow-up questions 
to make sure I understand things right:

> I think aux bus makes perfect sense when you have a clock/reset
> controller, but once you start expanding past that and you have reboot
> or hwmon or hwspinlock then mfd starts to make sense.

At what point does it make sense to move the bindings from bindings/clock to 
bindings/mfd? The controllers are still very clock-heavy. allwinner,*-
prcm.yaml look like clock, reset, misc controllers in mfd/ whereas 
ingenic,cgu.yaml, sprd,sc9863a-clk.yaml and da8xx-cfgchip.txt are clock + misc 
drivers in clock/.

Likewise for the node names: syscon@ or clock-controller@?

> You'd then have topclock that is a syscon + simple-mfd, matrixclk that is
> a syscon and lsp that's using the aux bus. The topclock and matrixclock
> would have dedicated and trivial drivers somewhere that have the mfd_cells
> and call mfd_add_devices().

Do I even need simple-mfd? It seems I can add the syscon-reboot node via 
mfd_cells too by setting .of_compatible. It seems once it has a driver (even a 
very short one) simple-mfd is misplaced.

What about syscon? Topclk needs it for syscon-reboot and the watchdog 
controls. For the other two I only want a regmap. Afaiu device_node_to_regmap 
works without a "syscon" compatible. There's also regmap_init_mmio, but afaics 
I only want this when my driver is the only one using the regmap.

> Probably the compatibles you've chosen start to make less sense at this
> point though, but probably "topclk" and "matrixclk" are not what the
> documentation for this device calls these register regions?

Yeah I'll rename them top topcrm / matrixcrm / lspcrm. I just stuck to the old 
names for this email.

> I think the priority is having something that reflects the hardware
> accurately, I wouldn't compromise on that just to have the same design
> for all three drivers.

As far as I can see the primary difference between mfd_add_devices and simple-
mfd + child nodes is that the latter makes the MFD composition visible in the 
device tree and the former keeps it a driver implementation detail. My sense 
is that the latter is preferred unless a subcomponent of the MFD might be 
reused in other components - e.g. an ADC is used in PMIC-abc and PMIC-xyz and 
thus the driver can be reused as well.

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