Re: [PATCH] Revert "bus: ti-sysc: Probe for l4_wkup and l4_cfg interconnect devices first"

[Tony Lindgren <tony@atomide.com>]

* Sverdlin, Alexander <alexander.sverdlin@siemens.com> [250319 07:39]:
> Hi Tony,
> 
> On Wed, 2025-03-19 at 05:56 +0200, Tony Lindgren wrote:
> > > > > > This reverts commit 4700a00755fb5a4bb5109128297d6fd2d1272ee6.
> > > > > > 
> > > > > > It brakes target-module@2b300050 ("ti,sysc-omap2") probe on AM62x in a case
>                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> [1]
> 
> > > > > > when minimally-configured system tries to network-boot:
> > > > > >    
> > > > > brakes or breaks? To unterstand the severity of the issue...  
> > > > 
> > > > Thanks for the correction, it should have been "breaks"...
> > > > 
> > > > > > [    6.888776] probe of 2b300050.target-module returned 517 after 258 usecs
> > > > > > [   17.129637] probe of 2b300050.target-module returned 517 after 708 usecs
> > > > > > [   17.137397] platform 2b300050.target-module: deferred probe pending: (reason unknown)
>                                   ^^^^^^^^^^^^^^^^^^^^^^
> 
> [2]
> 
> > > > > > [   26.878471] Waiting up to 100 more seconds for network.
> > > > > > 
> > > > > > Arbitrary 10 deferrals is really not a solution to any problem.  
> > > > > 
> > > > > So there is a point where no more probe of anything pending are
> > > > > triggered and therefore things are not probed?  
> > > > 
> > > > Because there is a point indeed (if we configure quite minimal set of drivers just
> > > > enough to mount NFS) when deferred probes are not triggered any longer.
> > > > 
> > > > > > Stable mmc enumeration can be achiever by filling /aliases node properly
> > > > > > (4700a00755fb commit's rationale).
> > > > > >    
> > > > > yes, it does not look like a clean solution. And we have the
> > > > > proper aliases node in many places. What I am a bit wondering about is
> > > > > what kind of sleeping dogs we are going to wake up by this revert. So I
> > > > > think this should be tested a lot esp. about possible pm issues.
> > > > > 
> > > > > Not every dependency in the sysc probe area is properly defined.  
> > > > 
> > > > But the patch I propose to revert is really not a solution for missing
> > > > dependencies on syscons. I'm fine with not propagating this to stable,
> > > > but reverting in master should give enough time for older SoCs to test,
> > > > WDYT?
> > > > 
> > > I am not against your revert proposal and not against propagating it
> > > to stable, I would just like to see some Tested-Bys before it gets
> > > applied to anything. If anything nasty pops up, it should be solved in a
> > > cleaner way then with the offending patch.
> > 
> > Sounds like for the AM62x problem there is simply some resource missing
> > that needs to be configured. Did you track down which resource is causing
> > the deferred probe without the revert?
> 
> This "missing" resource is pointed out above in [1] and [2].
> And it's missing only because of the arbitrary 10 deferrals, which simply
> do not happen on all systems if you'd configure less drivers or they are
> ordered in a way that 10 deferrals are not necessary in the DT.

Oh OK, sorry I misunderstood your problem. I thought you're missing some
resources like clocks or regulators. I did not realize this issue can
trigger on any system with just a few devices configured.

> If your patch is "fixing the root cause", could you please elaborate the
> number "10"? Why is it 10 and not 11 or 11000000?
> Could it be "2" or "1" as well?

Heh a random number enough to quiet down things was the original idea :)
Does not exactly always work as you pointed out.

Regards,

Tony