STM32: Clock control configuration moved from Kconfig to device tree


Erwan Gouriou
 

Hi,

We've started to transition STM32 clock system configuration from Kconfig to dts.

The main change (that introduces the whole mechanism) has been merged earlier this week,
making it available to L4/F4 and WB series:
It was followed by another change continuing the transition for remaining series 
(F0/F1/F2/F3/F7/G0/G4/L0/L1/L5/WL) and was merged earlier today.
The last change impacts H7 and is currently under review:

This series of changes allows to configure the whole stm32 clock system using
device tree, but for now, no extra modification is done in stm32 clock_control drivers. 

Kconfig style configuration is still functional but will be tagged as deprecated.
For now, only a couple of in tree boards have been converted to the new dts based
method.

I've raised an issue to track the mass conversion of the existing in tree boards
By the way, we're welcoming community contributions for this task!

Once all boards are converted, we'll be able to deprecate the Kconfig part,
which I hope could be done in DV2.6.0 timeframe.

During deprecation period, the stm32 clock_control developments involving 
device tree will be limited in order to keep backward compatibility with Kconfig.
This is done as a convenience for out of tree users. But for instance, code additions
like support of new series or PLLs will be implemented directly using device tree.

After the deprecation period, STM32 Kconfig clock_control part will be removed
and we'll be able to rework STM32 clock_control driver deeper and take advantage
of the benefits provided by device tree.

Don't hesitate to reach me on slack if you have questions.

Cheers
Erwan

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