Re: [PATCH 1/4] ARM: OMAP: usb-host: Device tree support for USB Host

[Roger Quadros <rogerq@ti.com>]

On 11/16/2012 01:06 PM, Benoit Cousson wrote:
> On 11/16/2012 11:55 AM, Roger Quadros wrote:
>> Hi Benoit,
>>
>> On 11/16/2012 12:30 PM, Benoit Cousson wrote:
>>> Hi Roger,
>>>
>>> On 11/15/2012 03:56 PM, Roger Quadros wrote:
>>>> Provides a means for the OMAP USB host subsystem to be initialized
>>>> from Device tree. This is a first step for device tree migration where
>>>> we specify only the board specific stuff. Things like I/O address space
>>>> and interrupts are not yet specified in the device tree but can be
>>>> done as a next step.
>>>>
>>>> This patch will allow boards to be booted with our without device tree
>>>> and have USB host functional.
>>>>
>>>> Signed-off-by: Roger Quadros <rogerq@ti.com>
>>>> ---
>>>>  .../devicetree/bindings/arm/omap/usb-host.txt      |   60 +++++++++++++++++
>>>>  arch/arm/mach-omap2/board-generic.c                |    1 +
>>>>  arch/arm/mach-omap2/common.h                       |    2 +
>>>>  arch/arm/mach-omap2/usb-host.c                     |   71 ++++++++++++++++++++
>>>>  4 files changed, 134 insertions(+), 0 deletions(-)
>>>>  create mode 100644 Documentation/devicetree/bindings/arm/omap/usb-host.txt
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/arm/omap/usb-host.txt b/Documentation/devicetree/bindings/arm/omap/usb-host.txt
>>>> new file mode 100644
>>>> index 0000000..f25cfa4
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/arm/omap/usb-host.txt
>>>> @@ -0,0 +1,60 @@
>>>> +* usb-host - OMAP USB Host Subsystem
>>>> +
>>>> +The OMAP USB host subsystem consists of the following modules
>>>> +1) USBTLL (Tranceiverless interface)
>>>> +2) USBHOST (Host Controller module) which includes both EHCI and OHCI controllers
>>>> +
>>>> +THe USB Host subsystem can be connected to the external world using 3 PORTs that could
>>>> +be configured in various modes like  UTMI+ for external PHY, ULPI transceiverless link (TLL),
>>>> +Serial TLL, High-speed interchip (HSIC), etc.
>>>> +
>>>> +Required proprties:
>>>> +- compatible: Must be "ti,usb-host";
>>>> +- num_ports: Number of physical ports available
>>>> +
>>>> +Optional properties:
>>>> +- 1 child node for each available port.  These child nodes are usually supplied by the
>>>> +  board support device tree as they are specific to how the ports are wired on the board
>>>> +
>>>> +  - mode: Integer specifying the mode in which the port is used
>>>> +	* OMAP_USBHS_PORT_MODE_UNUSED		= 0,
>>>> +	* OMAP_EHCI_PORT_MODE_PHY		= 1,
>>>> +	* OMAP_EHCI_PORT_MODE_TLL		= 2,
>>>> +	* OMAP_EHCI_PORT_MODE_HSIC		= 3,
>>>> +	* OMAP_OHCI_PORT_MODE_PHY_6PIN_DATSE0 	= 4,
>>>> +	* OMAP_OHCI_PORT_MODE_PHY_6PIN_DPDM 	= 5,
>>>> +	* OMAP_OHCI_PORT_MODE_PHY_3PIN_DATSE0	= 6,
>>>> +	* OMAP_OHCI_PORT_MODE_PHY_4PIN_DPDM	= 7,
>>>> +	* OMAP_OHCI_PORT_MODE_TLL_6PIN_DATSE0	= 8,
>>>> +	* OMAP_OHCI_PORT_MODE_TLL_6PIN_DPDM	= 9,
>>>> +	* OMAP_OHCI_PORT_MODE_TLL_3PIN_DATSE0	= 10,
>>>> +	* OMAP_OHCI_PORT_MODE_TLL_4PIN_DPDM	= 11,
>>>> +	* OMAP_OHCI_PORT_MODE_TLL_2PIN_DATSE0	= 12,
>>>> +	* OMAP_OHCI_PORT_MODE_TLL_2PIN_DPDM	= 13,
>>>> +   - clk: Name of the clock that needs to be active when using the port
>>>> +   - clkrate: Frequency at which the above clk needs to be run at
>>>> +
>>>> +
>>>> +Example:
>>>> +
>>>> +/* In the OMAP Core tree */
>>>> +usbhost: usb-host {
>>>> +	compatible = "ti,usb-host";
>>>> +	num_ports = <3>;
>>>> +};
>>>> +
>>>> +/* In the Board tree */
>>>> +&usbhost {
>>>> +	port@0 {
>>>> +		mode = <1>;
>>>> +		clk = "auxclk3_ck";
>>>> +		clkrate = <19200000>;
>>>> +	};
>>>> +	port@1 {
>>>> +		mode = <0>;
>>>> +	};
>>>> +	port@2 {
>>>> +		mode = <0>;
>>>> +	};
>>>> +};
>>>> +
>>>> diff --git a/arch/arm/mach-omap2/board-generic.c b/arch/arm/mach-omap2/board-generic.c
>>>> index 601ecdf..4e53b62 100644
>>>> --- a/arch/arm/mach-omap2/board-generic.c
>>>> +++ b/arch/arm/mach-omap2/board-generic.c
>>>> @@ -40,6 +40,7 @@ static void __init omap_generic_init(void)
>>>>  	omap_sdrc_init(NULL, NULL);
>>>>  
>>>>  	of_platform_populate(NULL, omap_dt_match_table, NULL, NULL);
>>>> +	usbhost_init_of();
>>>
>>> You should never have to add that kind of hacks in generic board file.
>>> Why do you need that during board init?
>>>
>>> In theory, the of_platform_populate will create all the devices, and
>>> during the driver probe you will create the sub nodes.
>>>
>>
>> OK. I was thinking of this as a temporary fix till the USB host drivers
>> support OF nodes natively. Maybe I should work on fixing up the host
>> drivers instead.
> 
> Well, yeah, that's clearly better.
> 
>> But I'm not sure how the PM runtime calls map to omap_device/hwmod
>> framework when device tree boot is used. I can see that the device tree
>> node can specify "ti,hwmods = " parameter. Just can't seem to figure out
>> how all this adds up :P
> 
> It is done auto-magically in the omap_device code. As soon as you add
> the "ti,hwmods: attribute, an omap_device will be created instead of a
> regular platform_device. A custom PM domain is added to handle the
> pm_runtime callback for OMAP IPs. And every omap_device belongs to that
> PM domain.
> 

Thanks. Just figured out it happens through BUS_NOTIFY_ADD_DEVICE ->
_omap_device_notifier_call() - > omap_device_build_from_dt()

cheers,
-roger