[U-Boot] [PATCH v2 2/4] board: ti: am57xx: Fix USB configuration

[Kishon Vijay Abraham I <kishon@ti.com>]

Hi Roger,

On Monday 16 May 2016 04:01 PM, Roger Quadros wrote:
> On 16/05/16 13:03, Kishon Vijay Abraham I wrote:
>> Hi Roger,
>>
>> On Monday 16 May 2016 03:19 PM, Roger Quadros wrote:
>>> On 16/05/16 12:26, Roger Quadros wrote:
>>>> On 16/05/16 12:06, Roger Quadros wrote:
>>>>> On 13/05/16 15:45, Marek Vasut wrote:
>>>>>> On 05/13/2016 02:36 PM, Roger Quadros wrote:
>>>>>>> Currently CONFIG_USB_DWC3 is not selected so doing a usb start
>>>>>>> command results in a serious error [1].
>>>>>>
>>>>>> Why does this error happen ? That is what should be fixed. Selecting
>>>>>> some random options seems like papering over a bug.
>>>>>
>>>>> Agreed. I was lazy :P.
>>>>
>>>> OK. The issue is like this.
>>>>
>>>> CONFIG_CMD_USB and CONFIG_USB_XHCI is defined, so usb_init() calls
>>>> usb_lowlevel_init() in xhci.c which calls xhci_hcd_init in xhci-omap.c which calls
>>>> board_usb_init().
>>
>> IIRC, board_usb_init for xhci (omap) is mostly a NOP.
> 
> Then who will call board_usb_init() for host case?
> 
>>>>
>>>> But board_usb_init() in am57xx/board.c is defined only if CONFIG_USB_DWC3 is defined
>>>> and that is missing in am57xx_evm.h leading to the serious error. We're trying to
>>>> access the IP without turning on the necessary clocks.
>>
>> clocks are not turned on in board_usb_init() right? The board_usb_init() in
>> am57xx/board.c is used only for gadget mode.
>>>>
>>>> So it looks like we need to define it based on CONFIG_USB_XHCI_OMAP or something else.
>>
>> right, but before that we might have to cleanup xhci-omap.
>>>>
>>>> But then again looking into the future, what if we want only gadget operation?
>>>> That would not define XHCI, but we still need board_usb_init(). So board_usb_init()
>>>> should be defined based on CONFIG_CMD_USB=y?
>>>>
>>>> What do you suggest?
>>>
>>> But board_usb_init() calls 
>>>
>>>                 ti_usb_phy_uboot_init(&usb_phy1_device);
>>>                 dwc3_omap_uboot_init(&usb_otg_ss1_glue);
>>>                 dwc3_uboot_init(&usb_otg_ss1);
>>>
>>> which depend on CONFIG_USB_DWC3_PHY_OMAP, CONFIG_USB_DWC3_OMAP and CONFIG_USB_DWC3
>>> respectively.
>>
>> IMO we should cleanup xhci-omap so that all the initializations are done using
>> ti_usb_phy_uboot_init, dwc3_omap_uboot_init and dwc3_uboot_init. Then modify
>> dwc3_uboot_init to initialize host or device based on CONFIG_*.
>>
> 
> I'm still trying to get a grip of how USB works in u-boot.
> Is CONFIG_CMD_USB only meant for host mode or gadget mode as well?

IIRC it is only for host. Commands like usb start, usb stop are used to start
and stop host.
> Is dual-role even required in u-boot? probably it is not a good idea and we just
> ignore it for simplicity.

yeah.
> 
> What determines whether a USB port is meant for Host or device operation? Is it
> the CONFIG_ or caller of board_usb_init()?
It should be the caller of board_usb_init(). The same port can be used as
device or host based on command used (the command determines the caller of
board_usb_init).

Thanks
Kishon