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

    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.

    All output is with #define DEBUG in drivers/of/property.c, and with
    CONFIG_SPI_DEBUG=y.

    Note that your patch has no impact on drivers/of/unittest.c, as that
    checks only internal DT structures, not actual device instantiation.

    Thanks! ;-)

    [1] https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git/diff/arch/arm64/boot/dts/renesas/r8a77990-ebisu-cn41-msiof0-25lc040.dtso?h=topic/renesas-overlays&id=86d0cf6fa7f191145380485c22f684873c5cce26

    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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