Re: [PATCH v1 5/5] driver core: Set fw_devlink=on by default

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Dec 17, 2020 at 07:17:03PM -0800, Saravana Kannan 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@google.com>

This patch breaks nios2 boot tests in qemu. The system gets stuck when
trying to reboot. Reverting this patch fixes the problem. Bisect log
is attached.

It may also break a variety of other boot tests, but with 115 of 430
boot tests failing in -next it is difficult to identify all culprits.

Guenter

---
Bisect log:

# bad: [a4bfd8d46ac357c12529e4eebb6c89502b03ecc9] Add linux-next specific files for 20210209
# good: [92bf22614b21a2706f4993b278017e437f7785b3] Linux 5.11-rc7
git bisect start 'HEAD' 'v5.11-rc7'
# good: [a8eb921ba7e8e77d994a1c6c69c8ef08456ecf53] Merge remote-tracking branch 'crypto/master'
git bisect good a8eb921ba7e8e77d994a1c6c69c8ef08456ecf53
# good: [21d507c41bdf83f6afc0e02976e43c10badfc6cd] Merge remote-tracking branch 'spi/for-next'
git bisect good 21d507c41bdf83f6afc0e02976e43c10badfc6cd
# bad: [30cd4c688a3bcf324f011d7716044b1a4681efc1] Merge remote-tracking branch 'soundwire/next'
git bisect bad 30cd4c688a3bcf324f011d7716044b1a4681efc1
# good: [c43d2173d3eb4047bb62a7a393a298a1032cce18] Merge remote-tracking branch 'drivers-x86/for-next'
git bisect good c43d2173d3eb4047bb62a7a393a298a1032cce18
# bad: [4dd66c506de68a592f2dd4ef64cc9b0d7c0f3117] Merge remote-tracking branch 'usb-chipidea-next/for-usb-next'
git bisect bad 4dd66c506de68a592f2dd4ef64cc9b0d7c0f3117
# good: [29b01295a829fba7399ee84afff4e64660e49f04] usb: typec: Add typec_partner_set_pd_revision
git bisect good 29b01295a829fba7399ee84afff4e64660e49f04
# bad: [dac8ab120e531bf7c358b85750338e1b3d3ca0b9] Merge remote-tracking branch 'usb/usb-next'
git bisect bad dac8ab120e531bf7c358b85750338e1b3d3ca0b9
# good: [678481467d2e1460a49e626d8e9ba0c7e9742f53] usb: dwc3: core: Check maximum_speed SSP genXxY
git bisect good 678481467d2e1460a49e626d8e9ba0c7e9742f53
# good: [5d3d0a61479847a8729ffdda33867f6b3443c15f] Merge remote-tracking branch 'ipmi/for-next'
git bisect good 5d3d0a61479847a8729ffdda33867f6b3443c15f
# bad: [e13f5b7a130f7b6d4d34be27a87393890b5ee2ba] of: property: Add fw_devlink support for "gpio" and "gpios" binding
git bisect bad e13f5b7a130f7b6d4d34be27a87393890b5ee2ba
# good: [b0e2fa4f611bb9ab22928605d5b1c7fd44e73955] driver core: Handle cycles in device links created by fw_devlink
git bisect good b0e2fa4f611bb9ab22928605d5b1c7fd44e73955
# bad: [0fab972eef49ef8d30eb91d6bd98861122d083d1] drivers: core: Detach device from power domain on shutdown
git bisect bad 0fab972eef49ef8d30eb91d6bd98861122d083d1
# bad: [e590474768f1cc04852190b61dec692411b22e2a] driver core: Set fw_devlink=on by default
git bisect bad e590474768f1cc04852190b61dec692411b22e2a
# good: [c13b827927112ba6170bea31c638a8573c127461] driver core: fw_devlink_relax_cycle() can be static
git bisect good c13b827927112ba6170bea31c638a8573c127461
# first bad commit: [e590474768f1cc04852190b61dec692411b22e2a] driver core: Set fw_devlink=on by default