[PATCH usb-next v6 0/3] initialize (multiple) PHYs on the roothub

Martin Blumenstingl martin.blumenstingl at googlemail.com
Thu Oct 19 14:32:31 PDT 2017

Hi Chunfeng Yun,

many thanks for your efforts (testing and explaining the Mediatek SoC
implementatino) on the earlier versions of this series!

On Tue, Oct 17, 2017 at 11:20 PM, Martin Blumenstingl
<martin.blumenstingl at googlemail.com> wrote:
> This series is the outcome of a discussion with Felipe Balbi,
> see [0] and [1] as well as Mathias Nyman, see [7] and [8].
> 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 "roothub PHY wrapper". This can be configured
> through devicetree by passing a child-node with "reg = <0>" (in other
> words: it describes the roothub) 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 roothub PHY wrapper into hcd.c
> which automatically enables it for all USB controller drivers (tested
> on an Amlogic Meson GXL SoC which uses a dwc3 controller).
> Changes since RfC v5 at [10]:
> - dropped RfC prefix
> - removed noisy dev_err if no roothub node was found (spotted by
>   Xiaolong Ye's kbuild test robot - thank you for that!)
> - moved the call to usb_phy_roothub_power_off() within
>   hcd_bus_suspend() to make sure that the PHYs are turned off
>   if the "race with a root-hub wakeup event" condition is met (in
>   this case the PHYs are turned on again, with the old code we did
>   break the PHYs internal ref-counting because we never turned the
>   PHYs off before turning them on again in case of that special
>   "race with a root-hub wakeup event").
>   additionally we're not handling the status returned by
>   usb_phy_roothub_power_off() anymore (the bus is already turned off
>   and we tried to turn off all PHYs as well - only the PHYs which
>   failed to power off will stay in the current state).
>   thanks to Alan Stern for the suggestion
> - removed return value from usb_phy_roothub_power_off() because none
>   of my code uses it anymore. thanks to Alan Stern for the suggestion
> Changes since v4 at [9]:
> - renamed the subject of the cover-letter (old name was:
>   "initialize (multiple) PHYs in xhci-plat")
> - back into RFC status (see below for the reasons)
> - dropped Tested-by from Chunfeng Yun (same reasons as RFC status)
> - reworded cover-letter and commit messages from "platform-roothub"
>   to "roothub PHY wrapper"
is there a chance you can test v6 of this series on the Mediatek SoCs
one more time?
in v5 the code was moved from xhci-plat.c to drivers/usb/core/hub.c
which should even enable it on non-xHCI controllers.
however, I cannot test suspend/resume support on my Meson GXL SoCs -
and in addition to that it would be awesome to have confirmation from
you that the latest version still works fine on the Mediatek SoCs

thank you in advance!

> - moved code from drivers/usb/host/platform-roothub.* to
>   drivers/usb/core/phy.* and the changes to
>   drivers/usb/host/xhci-plat.c to drivers/usb/core/hcd.c as suggested
>   by Mathias Nyman (as a benefit this will enable the new logic for
>   non-xHCI controllers as well - however this was not tested yet)
> - rename the structs, function names, etc from platform_roothub_* to
>   usb_phy_roothub*
> Changes since RFCv3 at [6]:
> - moved the DT binding change from patch #3 to patch #1 as suggested
>   by Rob Herring (and slightly adjusted the commit message to account
>   for that)
> - added Tested-by from Chunfeng Yun (who confirmed that the whole
>   concept and implementation works fine on Mediatek SoCs - many thanks
>   again!) to patch #2
> - added Rob Herring's ACK to patches 1 and 3
> - dropped RFC status (RFCv3 -> PATCH v4)
> 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
> [6] https://www.spinics.net/lists/devicetree/msg190426.html
> [7] http://lists.infradead.org/pipermail/linux-amlogic/2017-October/004881.html
> [8] http://lists.infradead.org/pipermail/linux-amlogic/2017-October/004920.html
> [9] http://lists.infradead.org/pipermail/linux-amlogic/2017-September/004685.html
> [10] http://lists.infradead.org/pipermail/linux-amlogic/2017-October/004924.html
> Martin Blumenstingl (3):
>   dt-bindings: usb: add the documentation for USB root-hub
>   usb: core: add a wrapper for the USB PHYs on the root-hub
>   usb: core: hcd: integrate the PHY roothub wrapper
>  .../devicetree/bindings/usb/usb-roothub.txt        |  46 ++++++
>  Documentation/devicetree/bindings/usb/usb-xhci.txt |   7 +
>  drivers/usb/core/Makefile                          |   2 +-
>  drivers/usb/core/hcd.c                             |  27 ++++
>  drivers/usb/core/phy.c                             | 176 +++++++++++++++++++++
>  drivers/usb/core/phy.h                             |   7 +
>  include/linux/usb/hcd.h                            |   1 +
>  7 files changed, 265 insertions(+), 1 deletion(-)
>  create mode 100644 Documentation/devicetree/bindings/usb/usb-roothub.txt
>  create mode 100644 drivers/usb/core/phy.c
>  create mode 100644 drivers/usb/core/phy.h
> --
> 2.14.2


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