Hello Saravana, On 7/1/19 5:48 PM, Saravana Kannan wrote: ... > TODO: > - For the case of consumer child sub-nodes being added by a parent > device after late_initcall_sync we might be able to address that by > recursively parsing all child nodes and adding all their suppliers as > suppliers of the parent node too. The parent probe will add the > children before its probe is completed and that will prevent the > supplier's sync_state from being executed before the children are > probed. > > But I'll write that part once I see how this series is received. I don't think that this scheme will work in all cases. It can also lead to probing deadlock. Here is an example: Three DT devices (top level A with subnodes B and C): /A /A/B /A/C C is a consumer of B. When device A is created, a search of its subnodes will find the link from C to B. Since device B hasn't been created yet, of_link_to_suppliers() will fail and add A to the wait_for_suppliers list. This will cause the probe of A to fail with -EPROBE_DEFER (thanks to the check in device_links_check_suppliers()). As a result device B will not be created and device A will never probe. You could try to resolve this situation by detecting the cycle and *not* adding A to the wait_for_suppliers list. However, that would get us back to the problem we had before. A would be allowed to probe which would then result in devices being added for B and C. If the device for B is added before C, then it would be allowed to immediately probe and (assuming this all takes place after late_initcall_sync thanks to modules) its sync_state() callback would be called since no consumer devices are linked to B. Please note that to change this example from theoretical to practical, replace "A" with apps_rsc, "B" with pmi8998-rpmh-regulators, and "C" with pm8998-rpmh-regulators in [1]. Take care, David [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/qcom/sdm845-mtp.dts?h=v5.2-rc7#n55 -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
