• Arnd Bergmann's avatar
    phy: work around 'phys' references to usb-nop-xceiv devices · b7563e27
    Arnd Bergmann authored
    Stefan Wahren reports a problem with a warning fix that was merged
    for v4.15: we had lots of device nodes with a 'phys' property pointing
    to a device node that is not compliant with the binding documented in
    This generally works because USB HCD drivers that support both the generic
    phy subsystem and the older usb-phy subsystem ignore most errors from
    phy_get() and related calls and then use the usb-phy driver instead.
    However, it turns out that making the usb-nop-xceiv device compatible with
    the generic-phy binding changes the phy_get() return code from -EINVAL to
    -EPROBE_DEFER, and the dwc2 usb controller driver for bcm2835 now returns
    -EPROBE_DEFER from its probe function rather than ignoring the failure,
    breaking all USB support on raspberry-pi when CONFIG_GENERIC_PHY is
    enabled. The same code is used in the dwc3 driver and the usb_add_hcd()
    function, so a reasonable assumption would be that many other platforms
    are affected as well.
    I have reviewed all the related patches and concluded that "usb-nop-xceiv"
    is the only USB phy that is affected by the change, and since it is by far
    the most commonly referenced phy, all the other USB phy drivers appear
    to be used in ways that are are either safe in DT (they don't use the
    'phys' property), or in the driver (they already ignore -EPROBE_DEFER
    from generic-phy when usb-phy is available).
    To work around the problem, this adds a special case to _of_phy_get()
    so we ignore any PHY node that is compatible with "usb-nop-xceiv",
    as we know that this can never load no matter how much we defer. In the
    future, we might implement a generic-phy driver for "usb-nop-xceiv"
    and then remove this workaround.
    Since we generally want older kernels to also want to work with the
    fixed devicetree files, it would be good to backport the patch into
    stable kernels as well (3.13+ are possibly affected), even though they
    don't contain any of the patches that may have caused regressions.
    Fixes: 014d6da6 ARM: dts: bcm283x: Fix DTC warnings about missing phy-cells
    Fixes: c5bbf358 arm: dts: nspire: Add missing #phy-cells to usb-nop-xceiv
    Fixes: 44e5dced arm: dts: marvell: Add missing #phy-cells to usb-nop-xceiv
    Fixes: f568f6f5 ARM: dts: omap: Add missing #phy-cells to usb-nop-xceiv
    Fixes: d745d5f2 ARM: dts: imx51-zii-rdu1: Add missing #phy-cells to usb-nop-xceiv
    Fixes: 915fbe59 ARM: dts: imx: Add missing #phy-cells to usb-nop-xceiv
    Link: https://marc.info/?l=linux-usb&m=151518314314753&w=2
    Link: https://patchwork.kernel.org/patch/10158145/
    Cc: stable@vger.kernel.org
    Cc: Felipe Balbi <balbi@kernel.org>
    Cc: Eric Anholt <eric@anholt.net>
    Tested-by: default avatarStefan Wahren <stefan.wahren@i2se.com>
    Acked-by: default avatarRob Herring <robh@kernel.org>
    Tested-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
    Acked-by: default avatarKishon Vijay Abraham I <kishon@ti.com>
    Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
phy-core.c 24.5 KB