[PATCH v6 05/12] power-domain: Add refcounting

[Francesco Dolcini]

On Mon, Apr 14, 2025 at 02:06:35PM -0600, Tom Rini wrote:
> On Mon, Apr 14, 2025 at 01:07:27PM -0500, Nishanth Menon wrote:
> > On 23:06-20250414, Francis, Neha wrote:
> > > On 4/3/2025 1:09 PM, Miquel Raynal wrote:
> > > > It is very surprising that such an uclass, specifically designed to
> > > > handle resources that may be shared by different devices, is not keeping
> > > > the count of the number of times a power domain has been
> > > > enabled/disabled to avoid shutting it down unexpectedly or disabling it
> > > > several times.
> > > > 
> > > > Doing this causes troubles on eg. i.MX8MP because disabling power
> > > > domains can be done in recursive loops were the same power domain
> > > > disabled up to 4 times in a row. PGCs seem to have tight FSM internal
> > > > timings to respect and it is easy to produce a race condition that puts
> > > > the power domains in an unstable state, leading to ADB400 errors and
> > > > later crashes in Linux.
> > > > 
> > > > CI tests using power domains are slightly updated to make sure the count
> > > > of on/off calls is even and the results match what we *now* expect.
> > > > 
> > > > As we do not want to break existing users while stile getting
> > > > interesting error codes, the implementation is split between:
> > > > - a low-level helper reporting error codes if the requested transition
> > > >   could not be operated,
> > > > - a higher-level helper ignoring the "non error" codes, like EALREADY and
> > > >   EBUSY.
> > > > 
> > > > Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
> > > > ---
> > > 
> > > This commit looks to be breaking K3 platforms boot, please see "Latest Boot
> > > Summary" [0]. Reverting the commit fixes boot.
> > > 
> > > [0] https://lcpd.itg.ti.com/upstream/k3-boot-build/main/build-trends.html
> > 
> > Uggh. This link is a TI internal link. Nutshell, it is broken
> > between:
> > v2025.04-921-gcb7555e93075 : https://source.denx.de/u-boot/u-boot.git
> > and
> > v2025.04-1041-g407d68638fe3 : https://source.denx.de/u-boot/u-boot.git
> > 
> > Neha bisected it down to 197376fbf300e92afa0a1583815d9c9eb52d613a commit
> > which is this patch.
> 
> And assuming it's the same failure I got reported this morning by one of
> my coworkers, we just get:
> U-Boot SPL 2025.04-01050-ga40fc5afaec0 (Apr 14 2025 - 07:31:32 +0000)
> SYSFW ABI: 3.1 (firmware rev 0x0009 '9.2.7--v09.02.07 (Kool Koala)')

I have not tried reverting that commit yet, but I do have the same
failure.

Francesco