netdev - Re: [PATCH v2 1/9] PM: domains: Delete usage of driver_deferred_probe_check

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Date:   Mon, 27 Jun 2022 12:10:20 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        iommu@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-gpio@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Alexander Stein <alexander.stein@...tq-group.com>
Subject: Re: [PATCH v2 1/9] PM: domains: Delete usage of
 driver_deferred_probe_check_state()

* Saravana Kannan <saravanak@...gle.com> [220623 08:17]:
> On Thu, Jun 23, 2022 at 12:01 AM Tony Lindgren <tony@...mide.com> wrote:
> >
> > * Saravana Kannan <saravanak@...gle.com> [220622 19:05]:
> > > On Tue, Jun 21, 2022 at 9:59 PM Tony Lindgren <tony@...mide.com> wrote:
> > > > This issue is no directly related fw_devlink. It is a side effect of
> > > > removing driver_deferred_probe_check_state(). We no longer return
> > > > -EPROBE_DEFER at the end of driver_deferred_probe_check_state().
> > >
> > > Yes, I understand the issue. But driver_deferred_probe_check_state()
> > > was deleted because fw_devlink=on should have short circuited the
> > > probe attempt with an  -EPROBE_DEFER before reaching the bus/driver
> > > probe function and hitting this -ENOENT failure. That's why I was
> > > asking the other questions.
> >
> > OK. So where is the -EPROBE_DEFER supposed to happen without
> > driver_deferred_probe_check_state() then?
> 
> device_links_check_suppliers() call inside really_probe() would short
> circuit and return an -EPROBE_DEFER if the device links are created as
> expected.

OK

> > Hmm so I'm not seeing any supplier for the top level ocp device in
> > the booting case without your patches. I see the suppliers for the
> > ocp child device instances only.
> 
> Hmmm... this is strange (that the device link isn't there), but this
> is what I suspected.

Yup, maybe it's because of the supplier being a device in the child
interconnect for the ocp.

> Now we need to figure out why it's missing. There are only a few
> things that could cause this and I don't see any of those. I already
> checked to make sure the power domain in this instance had a proper
> driver with a probe() function -- if it didn't, then that's one thing
> that'd could have caused the missing device link. The device does seem
> to have a proper driver, so looks like I can rule that out.
> 
> Can you point me to the dts file that corresponds to the specific
> board you are testing this one? I probably won't find anything, but I
> want to rule out some of the possibilities.

You can use the beaglebone black dts for example, that's
arch/arm/boot/dts/am335x-boneblack.dts and uses am33xx.dtsi for
ocp interconnect with simple-pm-bus.

> All the device link creation logic is inside drivers/base/core.c. So
> if you can look at the existing messages or add other stuff to figure
> out why the device link isn't getting created, that'd be handy. In
> either case, I'll continue staring at the DT and code to see what
> might be happening here.

In device_links_check_suppliers() I see these ocp suppliers:

platform ocp: device_links_check_suppliers: 1024: supplier 44e00d00.prm: link->status: 0 link->flags: 000001c0
platform ocp: device_links_check_suppliers: 1024: supplier 44e01000.prm: link->status: 0 link->flags: 000001c0
platform ocp: device_links_check_suppliers: 1024: supplier 44e00c00.prm: link->status: 0 link->flags: 000001c0
platform ocp: device_links_check_suppliers: 1024: supplier 44e00e00.prm: link->status: 0 link->flags: 000001c0
platform ocp: device_links_check_suppliers: 1024: supplier 44e01100.prm: link->status: 0 link->flags: 000001c0
platform ocp: device_links_check_suppliers: 1024: supplier fixedregulator0: link->status: 1 link->flags: 000001c0

No -EPROBE_DEFER is returned in device_links_check_suppliers() for
44e00c00.prm supplier for beaglebone black for example, 0 gets
returned.

Regards,

Tony