Re: [PATCH 0/2] power-domain: Enable uclass refcounting

[Wadim Egorov <w.egorov@phytec.de>]

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-v6-5-478b5e3dd872@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.