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Enable fw_devlink=on by default

Saravana Kannan linux-pci linux-renesas-soc linux-samsung-soc linux-tegra lkml oe-kbuild-all 1 version In review

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  1. v1 Latest5 patches 74 repliesIn review

Patches in v1 No applies recorded yet

#Subject and filesSizeRepliesApplied
1/5driver core: Add debug logs for device link related probe deferralsdrivers/base/core.c+6 -00 replies
2/5driver core: Add device link support for INFERRED flagdrivers/base/core.c include/linux/device.h+13 -40 replies
3/5driver core: Have fw_devlink use DL_FLAG_INFERREDdrivers/base/core.c+14 -80 replies
4/5driver core: Handle cycles in device links created by fw_devlinkdrivers/base/core.c+57 -10 replies
5/5driver core: Set fw_devlink=on by defaultdrivers/base/core.c+1 -146 replies

Reviews trailers per patch

None of the 5 patches has a Reviewed-by or Acked-by.

PatchJon Hunter
SeriesT-b
1/5
2/5
3/5
4/5
5/5

Trailers given in replies are filled; those carried in the patches from earlier versions are outlined with dashes.

Read the v1 thread

Cover letter [PATCH v1 0/5] Enable fw_devlink=on by default

As discussed in LPC 2020, cyclic dependencies in firmware that couldn't be broken using logic was one of the last remaining reasons fw_devlink=on couldn't be set by default.

This series changes fw_devlink so that when a cyclic dependency is found in firmware, the links between those devices fallback to permissive mode behavior. This way, the rest of the system still benefits from fw_devlink, but the ambiguous cases fallback to permissive mode.

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).

Greg/Rafael,

Can we get this pulled into 5.11-rc1 or -rc2 soon please? I expect to see some issues due to device drivers that aren't following best practices (they don't expose the device to driver core). Want to identify those early on and try to have them fixed before 5.11 release. See [1] for an example of such a case.

If we do end up have to revert anything, it'll just be Patch 5/5 (a one liner).

Marc,

You had hit issues with fw_devlink=on before on some of your systems. Want to give this a shot?

Jisheng,

Want to fix up one of those gpio drivers you were having problems with?

Thanks,
Saravana

[1] - https://lore.kernel.org/lkml/CAGETcx9PiX==mLxB9PO8Myyk6u2vhPVwTMsA5NkD-ywH5xhusw@mail.gmail.com/

Cc Jisheng Zhang <[email protected]>
Cc Kevin Hilman <[email protected]>
Cc John Stultz <[email protected]>
Cc Nicolas Saenz Julienne <[email protected]>
Cc Marc Zyngier <[email protected]>

Saravana Kannan (5):
driver core: Add debug logs for device link related probe deferrals driver core: Add device link support for INFERRED flag driver core: Have fw_devlink use DL_FLAG_INFERRED
driver core: Handle cycles in device links created by fw_devlink driver core: Set fw_devlink=on by default

 drivers/base/core.c    | 101 +++++++++++++++++++++++++++++++++++------
 include/linux/device.h |   2 +
 2 files changed, 90 insertions(+), 13 deletions(-)
Signature · 1 line
2.29.2.684.gfbc64c5ab5-goog

Read the cover letter in its thread