Re: [PATCH v4 00/13] USB: OTG/DRD Core functionality
From: Peter Chen
Date: Wed Aug 26 2015 - 03:31:32 EST
On Mon, Aug 24, 2015 at 04:21:11PM +0300, Roger Quadros wrote:
> This series centralizes OTG/Dual-role functionality in the kernel.
> As of now I've got Dual-role functionality working pretty reliably on
> dra7-evm and am437x-gp-evm.
> DWC3 controller and platform related patches will be sent separately.
I will review this patch set after you send the above, it will be
more clear if there are users for code.
> Series is based on Greg's usb-next tree.
> - Added DT support for tying otg-controller to host and gadget
> controllers. For DT we no longer have the constraint that
> OTG controller needs to be parent of host and gadget. They can be
> tied together using the "otg-controller" property.
> - Relax the requirement for DT case that otg controller must register before
> host/gadget. We maintain a wait list of host/gadget devices
> waiting on the otg controller.
> - Use a single struct usb_otg for otg data.
> - Don't override host/gadget start/stop APIs. Let the controller
> drivers do what they want as they know best. Helper API is provided
> for controller start/stop that controller driver can use.
> - Introduce struct usb_otg_config to pass the otg capabilities,
> otg ops and otg timer timeouts during otg controller registration.
> - rebased on Greg's usb.git/usb-next
> - all otg related definations now in otg.h
> - single kernel config USB_OTG to enable OTG core and FSM.
> - resolved symbol dependency issues.
> - use dev_vdbg instead of VDBG() in usb-otg-fsm.c
> - rebased on v4.2-rc1
> - Use add/remove_hcd() instead of start/stop_hcd() to enable/disable
> the host controller
> - added dual-role-device (DRD) state machine which is a much simpler
> mode of operation when compared to OTG. Here we don't support fancy
> OTG features like HNP, SRP, on the fly role-swap. The mode of operation
> is determined based on ID pin (cable type) and the role doesn't change
> till the cable type changes.
> Most of the OTG drivers have been dealing with the OTG state machine
> themselves and there is a scope for code re-use. This has been
> partly addressed by the usb/common/usb-otg-fsm.c but it still
> leaves the instantiation of the state machine and OTG timers
> to the controller drivers. We re-use usb-otg-fsm.c but
> go one step further by instantiating the state machine and timers
> thus making it easier for drivers to implement OTG functionality.
> Newer OTG cores support standard host interface (e.g. xHCI) so
> host and gadget functionality are no longer closely knit like older
> cores. There needs to be a way to co-ordinate the operation of the
> host and gadget in OTG mode. i.e. to stop and start them from a
> central location. This central location should be the USB OTG core.
> Host and gadget controllers might be sharing resources and can't
> be always running. One has to be stopped for the other to run.
> This can't be done as of now and can be done from the OTG core.
> The OTG core instantiates the OTG/DRD Finite State Machine
> per OTG controller and manages starting/stopping the
> host and gadget controllers based on the bus state.
> It provides APIs for the following
> - Registering an OTG capable controller
> struct otg_fsm *usb_otg_register(struct device *dev,
> struct usb_otg_config *config);
> int usb_otg_unregister(struct device *dev);
> - Registering Host controllers to OTG core (used by hcd-core)
> int usb_otg_register_hcd(struct usb_hcd *hcd, unsigned int irqnum,
> unsigned long irqflags, struct otg_hcd_ops *ops);
> int usb_otg_unregister_hcd(struct usb_hcd *hcd);
> - Registering Gadget controllers to OTG core (used by udc-core)
> int usb_otg_register_gadget(struct usb_gadget *gadget,
> struct otg_gadget_ops *ops);
> int usb_otg_unregister_gadget(struct usb_gadget *gadget);
> - Providing inputs to and kicking the OTG state machine
> void usb_otg_sync_inputs(struct otg_fsm *fsm);
> int usb_otg_kick_fsm(struct device *hcd_gcd_device);
> - Getting controller device structure from OTG state machine instance
> struct device *usb_otg_fsm_to_dev(struct otg_fsm *fsm);
> 'struct otg_fsm' is the interface to the OTG state machine.
> It contains inputs to the fsm, status of the fsm and operations
> for the OTG controller driver.
> - Helper APIs for starting/stopping host/gadget controllers
> int usb_otg_start_host(struct otg_fsm *fsm, int on);
> int usb_otg_start_gadget(struct otg_fsm *fsm, int on);
> Usage model:
> - The OTG core needs to know what host and gadget controllers are
> linked to the OTG controller. For DT boots we can provide that
> information by adding "otg-controller" property to the host and
> gadget controller nodes that points to the right otg controller.
> For legacy boot we assume that OTG controller is the parent
> of the host and gadget controllers. For DT if "otg-controller"
> property is not present then parent child relationship constraint
> - The OTG controller driver must call usb_otg_register() to register
> itself with the OTG core. It must also provide the required
> OTG configuration, fsm operations and timer timeouts (optional)
> via struct usb_otg_config. The fsm operations will be called
> depending on the OTG bus state.
> - The host/gadget core stacks are modified to inform the OTG core
> whenever a new host/gadget device is added. The OTG core then
> checks if the host/gadget is part of the OTG controller and if yes
> then prevents the host/gadget from starting till both host and
> gadget are registered, OTG state machine is running and the
> USB bus state is appropriate to start host/gadget.
> For this, APIs have been added to host/gadget stacks to start/stop
> the controllers from the OTG core.
> For DT boots, If the OTG controller hasn't yet been registered
> while the host/gadget are added, the OTG core will hold it in a wait list
> and register them when the OTG controller registers.
> - No modification is needed for the host/gadget controller drivers.
> They must ensure that their start/stop methods can be called repeatedly
> and any shared resources between host & gadget are properly managed.
> The OTG core ensures that both are not started simultaneously.
> - The OTG core instantiates one OTG state machine per OTG controller
> and the necessary OTG timers to manage OTG state timeouts.
> If none of the otg features are set during usb_otg_register() then it
> instanciates a DRD (dual-role device) state machine instead.
> The state machine is started when both host & gadget register and
> stopped when either of them unregisters. The controllers are started
> and stopped depending on bus state.
> - During the lifetime of the OTG state machine, inputs can be
> provided to it by modifying the appropriate members of 'struct otg_fsm'
> and calling usb_otg_sync_inputs(). This is typically done by the
> OTG controller driver that called usb_otg_register().
> Roger Quadros (13):
> usb: otg-fsm: Add documentation for struct otg_fsm
> usb: otg-fsm: support multiple instances
> usb: otg-fsm: Prevent build warning "VDBG" redefined
> otg-fsm: move usb_bus_start_enum into otg-fsm->ops
> usb: hcd.h: Add OTG to HCD interface
> usb: gadget.h: Add OTG to gadget interface
> usb: otg: add OTG core
> usb: doc: dt-binding: Add otg-controller property
> usb: chipidea: move from CONFIG_USB_OTG_FSM to CONFIG_USB_OTG
> usb: hcd: Adapt to OTG core
> usb: core: hub: Notify OTG fsm when A device sets b_hnp_enable
> usb: gadget: udc: adapt to OTG core
> usb: otg: Add dual-role device (DRD) support
> Documentation/devicetree/bindings/usb/generic.txt | 5 +
> Documentation/usb/chipidea.txt | 2 +-
> MAINTAINERS | 4 +-
> drivers/usb/Kconfig | 2 +-
> drivers/usb/Makefile | 1 +
> drivers/usb/chipidea/Makefile | 2 +-
> drivers/usb/chipidea/ci.h | 2 +-
> drivers/usb/chipidea/otg_fsm.c | 1 +
> drivers/usb/chipidea/otg_fsm.h | 2 +-
> drivers/usb/common/Makefile | 3 +-
> drivers/usb/common/usb-otg-fsm.c | 26 +-
> drivers/usb/common/usb-otg.c | 1223 +++++++++++++++++++++
> drivers/usb/common/usb-otg.h | 71 ++
> drivers/usb/core/Kconfig | 11 +-
> drivers/usb/core/hcd.c | 55 +-
> drivers/usb/core/hub.c | 10 +-
> drivers/usb/gadget/udc/udc-core.c | 124 ++-
> drivers/usb/phy/Kconfig | 2 +-
> drivers/usb/phy/phy-fsl-usb.c | 3 +
> include/linux/usb/gadget.h | 14 +
> include/linux/usb/hcd.h | 14 +
> include/linux/usb/otg-fsm.h | 116 +-
> include/linux/usb/otg.h | 191 +++-
> 23 files changed, 1808 insertions(+), 76 deletions(-)
> create mode 100644 drivers/usb/common/usb-otg.c
> create mode 100644 drivers/usb/common/usb-otg.h
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