This series is the outcome of a discussion with Felipe Balbi,
see [0] and [1].
The quick-summary of this is:
- dwc3 already takes one USB2 and one USB3 PHY and initializes these
correct
- some other HCI platform drivers (like ehci-platform.c, xhci-mtk.c and
ohci-platform.c) do not have a limitation on the number of PHYs - they
support one PHY per actual host port
- Amlogic Meson GXL and GXM SoCs come with a dwc3 IP block which has two
or three USB2 ports enabled on the internal root-hub. The SoCs also
provide separate USB2 PHYs, one per port. All USB2 PHYs (which are
internally "connected" to the dwc3 roothub) need to be powered on,
otherwise USB devices cannot be enumerated (even if just one PHY is
disabled and if the device is plugged into another, enabled port)
In my first attempt to get USB supported on the GXL and GXM SoCs I tried
to work-around the problem that I could not pass multiple PHYs to the
dwc3 controller.
This was rejected by Rob Herring (which was definitely the thing to do in
my opinion), see [2]
This series adds a new "platform-roothub". This can be configured through
devicetree by passing a child-node with "reg = <0>" to the USB
controller. Additionally there has to be a child-node for each port on
the root-hub. Each of the child-nodes takes a "phys" and "phy-names"
property. This allows modeling the root-hub in devicetree similar to the
USB device binding (documented in devicetree/bindings/usb/usb-device.txt)
This avoids and backwards-compatibility problems (which was a concern
regardless of the solution, see [3]) since the binding for the root-hub
was previously not specified (and we're not using the "phys" property of
the controller, which might have served different purposes before,
depending on the drivers).
Additionally this integrates the new platform-roothub into xhci-plat.c
which automatically enables it for the dwc3 driver (in host-mode).
Changes since RFCv2 at [5]:
- split phy_{init,exit} and phy_power_{on,off} handling. up until RFCv2
I called phy_init plus phy_power_on in platform_roothub_power_on and
phy_power_off plus phy_exit in platform_roothub_power_off. However,
Chunfeng Yun (a Mediatek SoC developer - many thanks for testing my
series and providing great feedback) reported that only using
phy_power_off (and omitting phy_exit) during system suspend fixes an
issue where USB devices would be re-enumerated when resuming. His
original problem description: "In order to keep link state on mt8173,
we just power off all phys(not exit) when system enter suspend, then
power on them again (needn't init, otherwise device will be
disconnected) when system resume, this can avoid re-enumerating
device.". This fix affects patch #2 and #3 as we now have
platform_roothub_init (which calls phy_init internally),
platform_roothub_power_on (which calls phy_power_on internally),
platform_roothub_power_off (which calls phy_power_off internally) and
platform_roothub_exit (which calls phy_exit internally). suspend and
resume only call platform_roothub_power_{on,off} to prevent the issue
described by Chunfeng Yun (unfortunately I cannot test this because
the Amlogic platform currently does not support system suspend).
- dropped two struct forward declarations from platform-roothub.h which
are not used in the header file (thanks to Chunfeng Yun for spotting
this)
Changes since RFCv1 at [4]:
- split the usb-xhci dt-binding documentation into a separate patch
- fixed a typo ("usb-phy" -> "phys" in the dt-binding example)
- rebased to apply against latest usb-next
[0] http://lists.infradead.org/pipermail/linux-amlogic/2017-January/001945.html
[1] http://lists.infradead.org/pipermail/linux-amlogic/2017-January/001947.html
[2] http://lists.infradead.org/pipermail/linux-amlogic/2016-November/001818.html
[3] http://lists.infradead.org/pipermail/linux-amlogic/2017-January/001948.html
[4] http://marc.info/?l=linux-usb&m=148414866303604&w=2
[5] https://www.spinics.net/lists/linux-usb/msg158967.html
Martin Blumenstingl (3):
dt-bindings: usb: add the documentation for USB root-hub
usb: host: add a generic platform USB roothub driver
usb: host: xhci: plat: integrate the platform-roothub
.../devicetree/bindings/usb/usb-roothub.txt | 46 ++++++
Documentation/devicetree/bindings/usb/usb-xhci.txt | 7 +
drivers/usb/host/Kconfig | 4 +
drivers/usb/host/Makefile | 2 +
drivers/usb/host/platform-roothub.c | 180 +++++++++++++++++++++
drivers/usb/host/platform-roothub.h | 12 ++
drivers/usb/host/xhci-plat.c | 35 +++-
drivers/usb/host/xhci.h | 2 +
8 files changed, 286 insertions(+), 2 deletions(-)
create mode 100644 Documentation/devicetree/bindings/usb/usb-roothub.txt
create mode 100644 drivers/usb/host/platform-roothub.c
create mode 100644 drivers/usb/host/platform-roothub.h
--
2.14.1
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