linux-kernel - Re: [PATCH v1 5/5] driver core: Set fw

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Date:   Tue, 19 Jan 2021 11:41:04 +0100
From:   Michael Walle <michael@...le.cc>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Jisheng Zhang <Jisheng.Zhang@...aptics.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        John Stultz <john.stultz@...aro.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        Kevin Hilman <khilman@...libre.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Marc Zyngier <maz@...nel.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        "Rafael J. Wysocki" <rafael@...nel.org>, minghuan.Lian@....com,
        mingkai.hu@....com, roy.zang@....com,
        Linux PCI <linux-pci@...r.kernel.org>
Subject: Re: [PATCH v1 5/5] driver core: Set fw_devlink=on by default

Am 2021-01-18 22:01, schrieb Saravana Kannan:
> On Sun, Jan 17, 2021 at 3:01 PM Michael Walle <michael@...le.cc> wrote:
>> > Cyclic dependencies in some firmware was one of the last remaining
>> > reasons fw_devlink=on couldn't be set by default. Now that cyclic
>> > dependencies don't block probing, set fw_devlink=on by default.
>> >
>> > Setting fw_devlink=on by default brings a bunch of benefits (currently,
>> > only for systems with device tree firmware):
>> > * Significantly cuts down deferred probes.
>> > * Device probe is effectively attempted in graph order.
>> > * Makes it much easier to load drivers as modules without having to
>> >   worry about functional dependencies between modules (depmod is still
>> >   needed for symbol dependencies).
>> >
>> > If this patch prevents some devices from probing, it's very likely due
>> > to the system having one or more device drivers that "probe"/set up a
>> > device (DT node with compatible property) without creating a struct
>> > device for it.  If we hit such cases, the device drivers need to be
>> > fixed so that they populate struct devices and probe them like normal
>> > device drivers so that the driver core is aware of the devices and their
>> > status. See [1] for an example of such a case.
>> >
>> > [1] - https://lore.kernel.org/lkml/CAGETcx9PiX==mLxB9PO8Myyk6u2vhPVwTMsA5NkD-ywH5xhusw@mail.gmail.com/
>> > Signed-off-by: Saravana Kannan <saravanak@...gle.com>
>> 
>> This breaks (at least) probing of the PCIe controllers of my board. 
>> The
>> driver in question is
>>   drivers/pci/controller/dwc/pci-layerscape.c
>> I've also put the maintainers of this driver on CC. Looks like it uses 
>> a
>> proper struct device. But it uses builtin_platform_driver_probe() and
>> apparently it waits for the iommu which uses module_platform_driver().
>> Dunno if that will work together.
> 
> Yeah, the builtin vs module doesn't matter. I've had fw_devlink work
> multiple times with the consumer driver being built in and the
> supplier actually loaded as a module. Making that work is one of the
> goals of fw_devlink.

Ok.

>> The board device tree can be found here:
>>   arch/arm64/boot/dts/freescale/fsl-ls1028a-kontron-sl28-var3-ads2.dts
>> 
>> Attached is the log with enabled "probe deferral" messages enabled.
> 
> I took a look at the logs. As you said, pci seems to be waiting on
> iommu, but it's not clear why the iommu didn't probe by then. Can you
> add initcall_debug=1 and enable the logs in device_link_add()? Btw, I
> realize one compromise on the logs is to send them as an attachment
> instead of inline. That way, it's still archived in the list, but I
> don't have to deal with log lines getting wrapped, etc.
> 
> Thanks for reporting the issues. Also, could you try picking up all of
> these changes and giving it a shot. It's unlikely to help, but I want
> to rule out issues related to fixes in progress.
> 
> https://lore.kernel.org/lkml/20210116011412.3211292-1-saravanak@google.com/
> https://lore.kernel.org/lkml/20210115210159.3090203-1-saravanak@google.com/
> https://lore.kernel.org/lkml/20201218210750.3455872-1-saravanak@google.com/

Did pick them up, the last one had a conflict due some superfluous 
lines.
Maybe they got reordered in that arrray.

Issue still persist. I've enabled the debug in device_link_add(), in
device_links_check_suppliers() and booted with initcall_debug. Please
see attached log. Lets see how that goes ;)

[    0.132687] calling  ls_pcie_driver_init+0x0/0x38 @ 1
[    0.132762] platform 3400000.pcie: probe deferral - supplier 
5000000.iommu not ready
[    0.132777] platform 3500000.pcie: probe deferral - supplier 
5000000.iommu not ready
[    0.132818] initcall ls_pcie_driver_init+0x0/0x38 returned -19 after 
119 usecs

After that, ls_pcie_driver_init() is never called again.

-michael
View attachment "boot.log" of type "text/plain" (149672 bytes)