fw_devlink=on breaks probing devices when of_platform_populate() is used

[Rafał Miłecki <zajec5@xxxxxxxxx>]

Hi,

I added of_platform_populate() calls in mtd subsystem in the commit
bcdf0315a61a2 ("mtd: call of_platform_populate() for MTD partitions"):
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bcdf0315a61a29eb753a607d3a85a4032de72d94

I recently backported that commit in OpenWrt to kernels 5.10 and 5.15.
We started receiving reports that probing Ethernet devices stopped
working in kernel 5.15. I bisected it down to the kernel 5.13 change:

commit ea718c699055c8566eb64432388a04974c43b2ea (refs/bisect/bad)
Author: Saravana Kannan <saravanak@xxxxxxxxxx>
Date:   Tue Mar 2 13:11:32 2021 -0800

    Revert "Revert "driver core: Set fw_devlink=on by default""

    This reverts commit 3e4c982f1ce75faf5314477b8da296d2d00919df.

    Since all reported issues due to fw_devlink=on should be addressed by
    this series, revert the revert. fw_devlink=on Take II.

    Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20210302211133.2244281-4-saravanak@xxxxxxxxxx
    Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

For me with above commit kernel just never calls bcm4908_enet_probe().
Reverting it from the top of 5.13.19 and 5.15.50 fixes it. I believe the
same issue happens with other drivers.

Critical detail is that in DT Ethernet block node references NVMEM cell
of MTD partition (see below).

Could you help me dealing with this issue, please? Can you see something
obvious breaking fw_devlink=on + of_platform_populate() case? Can I
provide some extra information to help fixing it?


Relevant DT part:

partitions {
	compatible = "fixed-partitions";
	#address-cells = <1>;
	#size-cells = <1>;

	partition@0 {
		compatible = "nvmem-cells";
		reg = <0x0 0x100000>;
		label = "bootloader";

		#address-cells = <1>;
		#size-cells = <1>;
		ranges = <0 0x0 0x100000>;

		base_mac_addr: mac@106a0 {
			reg = <0x106a0 0x6>;
		};
	};

	partition@100000 {
		reg = <0x100000 0x5700000>;
		label = "firmware";
	};
};

ethernet@2000 {
	compatible = "brcm,bcm4908-enet";
	reg = <0x2000 0x1000>;

	interrupts = <GIC_SPI 86 IRQ_TYPE_LEVEL_HIGH>,
			<GIC_SPI 87 IRQ_TYPE_LEVEL_HIGH>;
	interrupt-names = "rx", "tx";

	nvmem-cells = <&base_mac_addr>;
	nvmem-cell-names = "mac-address";
};

OpenWrt bug report:
https://github.com/openwrt/openwrt/issues/10232