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[ Upstream commit67cad5c670] fw_devlink uses DL_FLAG_SYNC_STATE_ONLY device link flag for two purposes: 1. To allow a parent device to proxy its child device's dependency on a supplier so that the supplier doesn't get its sync_state() callback before the child device/consumer can be added and probed. In this usage scenario, we need to ignore cycles for ensure correctness of sync_state() callbacks. 2. When there are dependency cycles in firmware, we don't know which of those dependencies are valid. So, we have to ignore them all wrt probe ordering while still making sure the sync_state() callbacks come correctly. However, when detecting dependency cycles, there can be multiple dependency cycles between two devices that we need to detect. For example: A -> B -> A and A -> C -> B -> A. To detect multiple cycles correct, we need to be able to differentiate DL_FLAG_SYNC_STATE_ONLY device links used for (1) vs (2) above. To allow this differentiation, add a DL_FLAG_CYCLE that can be use to mark use case (2). We can then use the DL_FLAG_CYCLE to decide which DL_FLAG_SYNC_STATE_ONLY device links to follow when looking for dependency cycles. Fixes:2de9d8e0d2("driver core: fw_devlink: Improve handling of cyclic dependencies") Signed-off-by: Saravana Kannan <saravanak@google.com> Tested-by: Colin Foster <colin.foster@in-advantage.com> Tested-by: Sudeep Holla <sudeep.holla@arm.com> Tested-by: Douglas Anderson <dianders@chromium.org> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> Tested-by: Luca Weiss <luca.weiss@fairphone.com> # qcom/sm7225-fairphone-fp4 Link: https://lore.kernel.org/r/20230207014207.1678715-6-saravanak@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.