Date:   Mon, 12 Dec 2022 16:06:35 +0300
From:   Maxim Kiselev <bigunclemax@...il.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Thorsten Leemhuis <regressions@...mhuis.info>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Vignesh Raghavendra <vigneshr@...com>,
        Richard Weinberger <richard@....at>,
        Maxim Kochetkov <fido_max@...ox.ru>,
        Rafał Miłecki <rafal@...ecki.pl>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>
Subject: Re: nvmem-cells regression after adding 'call of_platform_populate()
 for MTD partitions'

> At a first glance I don't get why the compatible would matter so much
> here, can you point to some core DT logic that would have an effect? I
> mean besides leading to the creation of a cell. IOW, what would be done
> differently if the compatible was different?

After adding a call of_platform_populate() for MTD partitions (bcdf0315)
we got a call of 'device_add' for each mtd partition which have
a 'compatible' property in its DT node. As a result any other devices
which have a DT reference to 'nvmem-cell' compatible mtd partition
got dependence from it (see attached log below). Now they will be waiting until
a 'nvmem-cell' device will be probed. But this will never happen because there
is no 'nvmem-cell' driver.


Here is part of kernel log after bcdf0315 commit:
  device: 'spi0.0': device_add
  spi-nor spi0.0: mx66l51235f (65536 Kbytes)
  7 fixed-partitions partitions found on MTD device spi0.0
  device: 'f1010600.spi:m25p80@0:partitions:partition@1': device_add
  device: 'platform:f1010600.spi:m25p80@0:partitions:partition@...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@...00 Dropping the fwnode link to partition@1
  Creating 7 MTD partitions on "spi0.0":
  platform f1070000.ethernet: error -EPROBE_DEFER: supplier
f1010600.spi:m25p80@0:partitions:partition@1 not ready
  devices_kset: Moving f1070000.ethernet to end of list
  platform f1070000.ethernet: error -EPROBE_DEFER: supplier
f1010600.spi:m25p80@0:partitions:partition@1 not ready

Here is part of kernel log with reverted bcdf0315 commit:
  device: 'spi0.0': device_add
  spi-nor spi0.0: mx66l51235f (65536 Kbytes)
  7 fixed-partitions partitions found on MTD device spi0.0
  Creating 7 MTD partitions on "spi0.0":
  ethernet@...00 Dropping the fwnode link to partition@1
  device: 'eth0': device_add
  mvneta f1070000.ethernet eth0: Using device tree mac address de:fa:ce:db:ab:e1

Look at strings below which exists only in the first log (with bcdf0315):
  device: 'f1010600.spi:m25p80@0:partitions:partition@1': device_add
  device: 'platform:f1010600.spi:m25p80@0:partitions:partition@...platform:f1070000.ethernet':
device_add
  platform f1070000.ethernet: error -EPROBE_DEFER: supplier
f1010600.spi:m25p80@0:partitions:partition@1 not ready


> because this just works with eeproms (non-mtd cells), so let's find out.
This works for eeproms and even for whole mtd partitions because there
are compatible drivers and those devices
can be probed, ulike a mtd subnode which is compatible with
non-existent 'nvmem-cell' driver.

пн, 12 дек. 2022 г. в 12:14, Miquel Raynal <miquel.raynal@...tlin.com>:
>
> Hi Maxim,
>
> bigunclemax@...il.com wrote on Sun, 11 Dec 2022 11:26:29 +0300:
>
> > >On 10.12.22 10:52, Maxim Kiselev wrote:
> > >>
> > >> After applying
> > >
> > >This makes me wonder: "applying" as in "applying it to some version that
> > >doesn't contain this change normally" or as it "after it was applied to
> > >mainline I have the following problem with vanilla kernel version <???>"?
> >
> > Sorry for confusing you, I mean "after it was applied to mainline".
> > I have this problem with vanilla kernel version 6.0.
> >
> > >>> I faced with a problem that my ethernet device can't be probed because it
> > >>> wait when 'nvmem-cells' device will be probed first.
> > >>
> > >>FWIW, there is a discussion about a problems that at least to my
> > >>untrained eyes looks similar:
> > >>https://lore.kernel.org/all/Yyj7wJlqJkCwObRn@lx2k/
> >
> > Yes it looks like the same issue.
> >
> >
> > I think the root of the problem was the choice of 'compatible'
> > device tree property to mark the mtd partition node as a nvmem provider.
> >
> > I'm talking about this part in 'mtd_nvmem_add' function.
> > > config.no_of_node = !of_device_is_compatible(node, "nvmem-cells");
> >
> > Maybe we should change the 'compatible' property to something else?
>
> At a first glance I don't get why the compatible would matter so much
> here, can you point to some core DT logic that would have an effect? I
> mean besides leading to the creation of a cell. IOW, what would be done
> differently if the compatible was different?
>
> Can you also dump the device links (if you can reach a prompt) from
> sysfs?
>
> In theory there should be a link between ethernet and spi-nor which is
> fulfilled when the spi-nor device probes and leads to the creation of
> device links. Maybe there is "something else" that the mtd core should
> do, because this just works with eeproms (non-mtd cells), so let's find
> out.
>
> > сб, 10 дек. 2022 г. в 15:35, Thorsten Leemhuis <regressions@...mhuis.info>:
> > >
> > > [CCing the regression mailing list, as it should be in the loop for all
> > > regressions, as explained in
> > > https://docs.kernel.org/admin-guide/reporting-regressions.html ]
> > >
> > > Hi, this is your Linux kernel regression tracker. Thx for the report.
> > >
> > > On 10.12.22 10:52, Maxim Kiselev wrote:
> > > >
> > > > After applying
> > >
> > > This makes me wonder: "applying" as in "applying it to some version that
> > > doesn't contain this change normally" or as it "after it was applied to
> > > mainline I have the following problem with vanilla kernel version <???>"?
> > >
> > > > this commit 'mtd: call of_platform_populate() for MTD
> > > > partitions' (bcdf0315),
> > >
> > > CCing Rafał, who authored 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.
> > >
> > > FWIW, there is a discussion about a problems that at least to my
> > > untrained eyes looks similar:
> > > https://lore.kernel.org/all/Yyj7wJlqJkCwObRn@lx2k/
> > >
> > > Rafał, has some progress been made to resolve this?
> > >
> > > To me it sounds like this might warrant a "revert, and reapply later
> > > when the cause for the regression was addressed". Rafał, it seems you
> > > suggested something like that, but it doesn't look like that happened
> > > for one reason or another. Or am I missing something?
> > >
> > > Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> > >
> > > P.S.: As the Linux kernel's regression tracker I deal with a lot of
> > > reports and sometimes miss something important when writing mails like
> > > this. If that's the case here, don't hesitate to tell me in a public
> > > reply, it's in everyone's interest to set the public record straight.
> > >
> > > > 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@...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@...00 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@...00 {
> > > >         status = "okay";
> > > >         nvmem-cells = <&macaddr>;
> > > >         nvmem-cell-names = "mac-address";
> > > >         phy-mode = "rgmii";
> > > >         phy = <&phy0>;
> > > >     };
> > > >
> > > >     spi@...00 {
> > > >         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@...00' requires 'macaddr: mac@6' which is
> > > > located inside mtd 'partition@1' of 'm25p80@0' spi flash.
> > >
> > > P.P.S.: let me add this to the regression tracking:
> > >
> > > #regzbot ^introduced bcdf0315
> > > #regzbot title mtd: ethernet device can't be probed anymore due to
> > > broken nvmem-cells dep
> > > #regzbot monitor: https://lore.kernel.org/all/Yyj7wJlqJkCwObRn@lx2k/
> > > #regzbot ignore-activity
>
>
> Thanks,
> Miquèl

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