On 30/05/16 12:29, Peter Chen wrote:

On Fri, May 13, 2016 at 01:03:14PM +0300, Roger Quadros wrote:

quoted

Hi,

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.
NOTE: my am437x-gp-evm broke so I couldn't test v8 on it.
But the changes since v7 are trivial and shouldn't impact am437x-gp-evm.

DWC3 controller and platform related patches will be sent separately.

Series is based on v4.6-rc1 and depends on first 2 patches of [1]
[1] - OTG fsm cleanup - https://lkml.org/lkml/2016/3/30/186

Why?:
----

Currently there is no central location where OTG/dual-role functionality is
implemented in the Linux USB stack and every USB controller driver is
doing their own thing for OTG/dual-role. We can benefit from code-reuse
and simplicity by adding the OTG/dual-role core driver.

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 controllers in dual-role mode. i.e. to stop and start them
from a central location. This central location should be the
USB OTG/dual-role 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 couldn't be done till now but can be done from the OTG core.

What?:
-----

The OTG/dual-role core consists of a set of APIs that allow
registration of OTG controller device and OTG capable host and gadget
controllers.

- The OTG controller driver can provide the OTG capabilities and the
Finite State Machine work function via 'struct usb_otg_config'
at the time of registration i.e. usb_otg_register();

	struct usb_otg *usb_otg_register(struct device *dev,
        	                         struct usb_otg_config *config);
	int usb_otg_unregister(struct device *dev);
	/**
	 * struct usb_otg_config - otg controller configuration
	 * @caps: otg capabilities of the controller
	 * @ops: otg fsm operations
	 * @otg_work: optional custom otg state machine work function
	 */
	struct usb_otg_config {
	        struct usb_otg_caps *otg_caps;
	        struct otg_fsm_ops *fsm_ops;
	        void (*otg_work)(struct work_struct *work);
	};

The dual-role state machine is built-into the OTG core so nothing
special needs to be provided if only dual-role functionality is desired.
The low level OTG controller driver ops are povided via
'struct otg_fsm_ops *fsm_ops' in the 'struct usb_otg_config'.

After registration, the OTG core waits for host, gadget controller
and the gadget function driver to be registered. Once all resources are
available it instantiates the Finite State Machine (FSM).
The host/gadget controllers are started/stopped according to the FSM.

- Host and gadget controllers that are a part of OTG/dual-role port must
use the OTG core provided APIs to add/remove the host/gadget.
i.e. hosts must use usb_otg_add_hcd() usb_otg_remove_hcd(),,
gadgets must use usb_otg_add_gadget_udc() usb_del_gadget_udc().
This ensures that the host and gadget controllers are not started till
the state machine is ready and the right bus conditions are met.
It also allows the host and gadget controllers to provide the OTG
controller device to link them together. For Device tree boots
the related OTG controller is automatically picked up via the
'otg-controller' property in the Host/Gadget controller nodes.

	int usb_otg_add_hcd(struct usb_hcd *hcd,
			    unsigned int irqnum, unsigned long irqflags,
			    struct device *otg_dev);
	void usb_otg_remove_hcd(struct usb_hcd *hcd);

	int usb_otg_add_gadget_udc(struct device *parent,
				   struct usb_gadget *gadget,
				   struct device *otg_dev);
	usb_del_gadget_udc() must be used for removal.


- During the lifetime of the FSM, the OTG controller driver can provide
inputs event changes using usb_otg_sync_inputs(). The OTG core will
then schedule the FSM work function (or internal dual-role state machine)
to update the FSM state. The FSM then calls the OTG controller
operations (fsm_ops) as necessary.
	void usb_otg_sync_inputs(struct usb_otg *otg);

- The following 2 functions are provided as helpers for use by the
OTG controller driver to start/stop the host/gadget controllers.
	int usb_otg_start_host(struct usb_otg *otg, int on);
	int usb_otg_start_gadget(struct usb_otg *otg, int on);

- The following function is provided for use by the USB host stack
to sync OTG related events to the OTG state machine.
e.g. change in host_bus->b_hnp_enable, gadget->b_hnp_enable
	int usb_otg_kick_fsm(struct device *otg_device);

Changelog:
---------
v8:
- split out start/stop gadget and connect/disconnect operations.
- make CONFIG_OTG dpend on CONFIG_USB_GADGET as well apart from CONFIG_USB
- use create_freezable_workqueue() for OTG work as per Peter's suggestion.
- remove usb-otg.h as we're not initializing any OTG timers.
- don't include unnecessary headers in usb-otg.c (i.e. hrtimer.h & ktime.h)

Since you have agreed to move CONFIG_USB_OTG out of HCD, I suggest you
can have a folder to put current OTG and OTG_FSM stuffs under the root
of usb folder, it can benefit the user who wants to add their dual-role
switch driver or OTG driver. What do you think?

Yes, I will give it a try and post if any problems.

--
cheers,
-roger
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