Am 25.04.25 um 09:49 schrieb Miquel Raynal:
On one side we have a power domain uclass which is mostly clueless about
the topology of the power domains it manages.
On the other side we have SoCs which are getting more and more complex,
ie. with several layers of power domains. Sometimes (eg. on TI K3
platforms) all power domains are defined by a single device tree node
and the "subdomains" are referenced using an identification
cell (#power-domain-cells = <1 or more>). Sometimes however (eg. on NXP
i.MX8 SoCs), the description uses many device tree nodes.
When a power domain is referenced several times, it is likely that the
power_domain_on() function will be called several times in a row, which
in some cases may lead to glitches or even breakages. This situation is
problematic on i.MX8MP and only with proper reference counting we can
safely support the video pipeline.
There was a first attempt to bring refcount support to the power domain
uclass, but it miserably failed because of the details mentioned
above:
https://lore.kernel.org/u-boot/20250403-ge-mainline-display-support-v6-5-478b5e3dd...@bootlin.com/
So here is a new version of it, which takes into consideration:
- the fact that a single power domain udev can target several power
domain IDs (referred as "subdomains")
- the fact that some platforms might count on a uneven count of on/off
calls to work, and "fixing" this may break the platforms.
So refcounting is an opt-in parameter, it is a matter of filling the
platform (public part of a per-uclass structure) subdomains number with
the number of subdomains this device nodes features (one per
power_domain->id) in the probe function of the power domain driver.
This series shows how it can be done by enabling refcounting on i.MX8MP.
Samuel, Neha, Wadim, Heiko, could you please confirm it works on your
side?
Booting works for me on the phycore-am62x.
