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    SubjectRe: [PATCH v3 09/12] of: property: Simplify of_link_to_phandle()
    Hi Saravana,

    On Wed, Feb 8, 2023 at 3:08 AM Saravana Kannan <saravanak@google.com> wrote:
    > On Tue, Feb 7, 2023 at 12:57 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
    > > On Tue, Feb 7, 2023 at 2:42 AM Saravana Kannan <saravanak@google.com> wrote:
    > > > The driver core now:
    > > > - Has the parent device of a supplier pick up the consumers if the
    > > > supplier never has a device created for it.
    > > > - Ignores a supplier if the supplier has no parent device and will never
    > > > be probed by a driver
    > > >
    > > > And already prevents creating a device link with the consumer as a
    > > > supplier of a parent.
    > > >
    > > > So, we no longer need to find the "compatible" node of the supplier or
    > > > do any other checks in of_link_to_phandle(). We simply need to make sure
    > > > that the supplier is available in DT.
    > > >
    > > > Signed-off-by: Saravana Kannan <saravanak@google.com>
    > >
    > > Thanks for your patch!
    > >
    > > This patch introduces a regression when dynamically loading DT overlays.
    > > Unfortunately this happens when using the out-of-tree OF configfs,
    > > which is not supported upstream. Still, there may be (obscure)
    > > in-tree users.
    > >
    > > When loading a DT overlay[1] to enable an SPI controller, and
    > > instantiate a connected SPI EEPROM:
    > >
    > > $ overlay add 25lc040
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /keys/status
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /soc/spi@e6e90000/pinctrl-0
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /soc/spi@e6e90000/pinctrl-names
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /soc/spi@e6e90000/cs-gpios
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /soc/spi@e6e90000/status
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /__symbols__/msiof0_pins
    > >
    > > The SPI controller and the SPI EEPROM are no longer instantiated.
    > >
    > > # cat /sys/kernel/debug/devices_deferred
    > > e6e90000.spi platform: wait for supplier msiof0
    > >
    > > Let's remove the overlay again:
    > >
    > > $ overlay rm 25lc040
    > > input: keys as /devices/platform/keys/input/input1
    > >
    > > And retry:
    > >
    > > $ overlay add 25lc040
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /keys/status
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /soc/spi@e6e90000/pinctrl-0
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /soc/spi@e6e90000/pinctrl-names
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /soc/spi@e6e90000/cs-gpios
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /soc/spi@e6e90000/status
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /__symbols__/msiof0_pins
    > > spi_sh_msiof e6e90000.spi: DMA available
    > > spi_sh_msiof e6e90000.spi: registered master spi0
    > > spi spi0.0: setup mode 0, 8 bits/w, 100000 Hz max --> 0
    > > at25 spi0.0: 512 Byte at25 eeprom, pagesize 16
    > > spi_sh_msiof e6e90000.spi: registered child spi0.0
    > >
    > > Now it succeeds, and the SPI EEPROM is available, and works.
    > >
    > > Without this patch, or with this patch reverted after applying the
    > > full series:
    > >
    > > $ overlay add 25lc040
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /keys/status
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /soc/spi@e6e90000/pinctrl-0
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /soc/spi@e6e90000/pinctrl-names
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /soc/spi@e6e90000/cs-gpios
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /soc/spi@e6e90000/status
    > > OF: overlay: WARNING: memory leak will occur if overlay removed,
    > > property: /__symbols__/msiof0_pins
    > > OF: Not linking spi@e6e90000 to interrupt-controller@f1010000 - No
    > > struct device
    > > spi_sh_msiof e6e90000.spi: DMA available
    > > spi_sh_msiof e6e90000.spi: registered master spi0
    > > spi spi0.0: setup mode 0, 8 bits/w, 100000 Hz max --> 0
    > > at25 spi0.0: 444 bps (2 bytes in 9 ticks)
    > > at25 spi0.0: 512 Byte at25 eeprom, pagesize 16
    > > spi_sh_msiof e6e90000.spi: registered child spi0.0
    > >
    > > The SPI EEPROM is available on the first try after boot.
    >
    > Sigh... I spent way too long trying to figure out if I caused a memory
    > leak. I should have scrolled down further! Doesn't look like that part
    > is related to anything I did.

    Please ignore the memory leak messages. They are known issues
    in the upstream DT overlay code, and not related to your series.

    > There are some flags set to avoid re-parsing fwnodes multiple times.
    > My guess is that the issue you are seeing has to do with how many of
    > the in memory structs are reused vs not when an overlay is
    > applied/removed and some of these flags might not be getting cleared
    > and this is having a bigger impact with this patch (because the fwnode
    > links are no longer anchored on "compatible" nodes).
    >
    > With/without this patch (let's keep the series) can you look at how
    > the following things change between each step you do above (add,
    > remove, retry):
    > 1) List of directories under /sys/class/devlink
    > 2) Enable the debug logs inside __fwnode_link_add(),
    > __fwnode_link_del(), device_link_add()

    Thanks, I'll give that a try, later...

    Gr{oetje,eeting}s,

    Geert

    --
    Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

    In personal conversations with technical people, I call myself a hacker. But
    when I'm talking to journalists I just say "programmer" or something like that.
    -- Linus Torvalds

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