driver core: fw_devlink: Make cycle detection more robust
fw_devlink could only detect a single and simple cycle because it relied mainly on device link cycle detection code that only checked for cycles between devices. The expectation was that the firmware wouldn't have complicated cycles and multiple cycles between devices. That expectation has been proven to be wrong. For example, fw_devlink could handle: +-+ +-+ |A+------> |B+ +-+ +++ ^ | | | +----------+ But it couldn't handle even something as "simple" as: +---------------------+ | | v | +-+ +-+ +++ |A+------> |B+------> |C| +-+ +++ +-+ ^ | | | +----------+ But firmware has even more complicated cycles like: +---------------------+ | | v | +-+ +---+ +++ +--+A+------>| B +-----> |C|<--+ | +-+ ++--+ +++ | | ^ | ^ | | | | | | | | | +---------+ +---------+ | | | +------------------------------+ And this is without including parent child dependencies or nodes in the cycle that are just firmware nodes that'll never have a struct device created for them. The proper way to treat these devices it to not force any probe ordering between them, while still enforce dependencies between node in the cycles (A, B and C) and their consumers. So this patch goes all out and just deals with all types of cycles. It does this by: 1. Following dependencies across device links, parent-child and fwnode links. 2. When it find cycles, it mark the device links and fwnode links as such instead of just deleting them or making the indistinguishable from proxy SYNC_STATE_ONLY device links. This way, when new nodes get added, we can immediately find and mark any new cycles whether the new node is a device or firmware node. Fixes: 2de9d8e0 ("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/20230207014207.1678715-9-saravanak@google.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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