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From:   Maxim Kiselev <bigunclemax@gmail.com>
Date:   Sat, 10 Dec 2022 12:52:12 +0300
Message-ID: <CALHCpMgEZjnR39upkR6iozSk-b5A_GHRo9rcDSPXzzQi6x_qCw@mail.gmail.com>
Subject: Fwd: nvmem-cells regression after adding 'call of_platform_populate()
 for MTD partitions'
To:     linux-mtd@lists.infradead.org
Cc:     linux-kernel@vger.kernel.org,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Richard Weinberger <richard@nod.at>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Maxim Kochetkov <fido_max@inbox.ru>,
        Maksim Kiselev <bigunclemax@gmail.com>
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Hi, friends.

After applying this commit 'mtd: call of_platform_populate() for MTD
partitions' (bcdf0315),
I faced with a problem that my ethernet device can't be probed because it
wait when 'nvmem-cells' device will be probed first.

But there is no such driver which is compatible with 'nvmem-cells' because
'nvmem-cells' is just a mark used by the 'mtd_nvmem_add' function.

So this leads to appeating of unresolved dependency for the ethernet device.
And that's why the ethernet device can't be added and probed.

Here is a part of kernel log when spi flash probe start:

> device: 'spi0': device_add
> device: 'spi0.0': device_add
> spi-nor spi0.0: mx66l51235f (65536 Kbytes)
> 7 fixed-partitions partitions found on MTD device spi0.0

After 'm25p80' probe 'f1070000.ethernet' linked to 'partition@1' :

> device: 'f1010600.spi:m25p80@0:
partitions:partition@1': device_add
> device: 'platform:f1010600.spi:m25p80@0:partitions:partition@1--platform:f1070000.ethernet': device_add
> devices_kset: Moving f1070000.ethernet to end of list
> platform f1070000.ethernet: Linked as a consumer to f1010600.spi:m25p80@0:partitions:partition@1
> ethernet@70000 Dropping the fwnode link to partition@1

And as a result I got `-EPROBE_DEFER` for `f1070000.ethernet`

> platform f1070000.ethernet: error -EPROBE_DEFER: supplier f1010600.spi:m25p80@0:partitions:partition@1 not ready

Here is a part of my device tree:

    enet1: ethernet@70000 {
        status = "okay";
        nvmem-cells = <&macaddr>;
        nvmem-cell-names = "mac-address";
        phy-mode = "rgmii";
        phy = <&phy0>;
    };

    spi@10600 {
        status = "okay";

        m25p80@0 {
            compatible = "mx66l51235l";
            reg = <0>;
            #address-cells = <1>;
            #size-cells = <1>;

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

                partition@0 {
                    reg = <0x00000000 0x000080000>;
                    label = "SPI.U_BOOT";
                };

                partition@1 {
                    compatible = "nvmem-cells";
                    reg = <0x000A0000 0x00020000>;
                    label = "SPI.INV_INFO";
                    #address-cells = <1>;
                    #size-cells = <1>;
                    ranges = <0 0x000A0000 0x00020000>;

                    macaddr: mac@6 {
                        reg = <0x6 0x6>;
                    };
                };

            };
        };
    };

In the example above 'ethernet@70000' requires 'macaddr: mac@6' which is
located inside mtd 'partition@1' of 'm25p80@0' spi flash.