[U-Boot] [PATCH 8/8] config: smdk5420: Enable support for multiple XHCI controllers

[Vivek Gautam]

On Tue, Jan 7, 2014 at 2:44 PM, Marek Vasut <marex at denx.de> wrote:
> On Tuesday, January 07, 2014 at 09:55:37 AM, Vivek Gautam wrote:
>> HI Marek,
>>
>>
>> On Mon, Jan 6, 2014 at 9:24 PM, Marek Vasut <marex at denx.de> wrote:
>>
>> Thanks for reviewing this. :-)
>>
>> > On Monday, January 06, 2014 at 10:29:43 AM, Vivek Gautam wrote:
>> >> Update USB_MAX_CONTROLLER_COUNT to be '2' to enable support
>> >> for both usb 3.0 controllers on exynos5420.
>> >>
>> >> NOTE: To use EHCI on exynos5420, this change will need to be
>> >> reverted, since there's only one EHCI controller available on
>> >> exynos5420.
>> >
>> > OK, this I seriously dislike. Hence a question ... my feeling is the XHCI
>> > and EHCI code for handling multiple controllers and multiple ports is
>> > almost the same. Can this code be adjusted to handle both EHCI and XHCI
>> > controllers indiscriminately ?
>>
>> The controller count is actually used by the usb core (common/usb*)
>> framework, right ?
>> There's a need to add support for multiple controller types actually
>> (so that EHCI
>> and XHCI can be enabled simultaneously). Is that what you mean here ?
>
> Yes. That should not be too much of a problem though.

True :-)

>
>> > This would result in having CONFIG_USB_MAX_CONTROLLER_COUNT 3 on this
>> > board and being able to use both EHCI and XHCI . Would this be possible
>> > for you to implement please ? Thanks !
>>
>> Ok, so you mean get all the controllers present on the board (EHCI and
>> XHCI) setup.
>
> Yes
>
>> I think right now, the way USB core handles the controller count is
>> quite different, so
>> that 'CONFIG_USB_MAX_CONTROLLER_COUNT' helps in probing multiple
>> controllers of the same type.
>
> The only problem is, that both EHCI and XHCI core implement:
>
> submit_control_msg()
> submit_bulk_msg()
> submit_int_msg()
> usb_lowlevel_init()
> usb_lowlevel_stop()

exactly.

>
> How I'd do this:
> 1) Rename all these submit_*() functions to usb_submit_*()
> 2) Rename all five usb_*() functions to ehci_*() resp. xhci_*()
This will happen in each controller drivers (ehci/xhci) which would
eventually be
called fro upper translation layer you mentioned below, right ?

> 3) Implement translation layer, where the common code would still call usb_*()
>    and the layer would determine whether to call ehci_*() or xhci_*() call.
>
> Surely, you'd need to change the probe() logic a bit, the controller drivers
> would have to call some "usb_register_driver()" function for each controller.
> This function would generate a new entry in a linked list of all controllers
> registered and would add a flag whether this controller is EHCI or XHCI.

Ok, i can understand this. Will try to put up code for this.

>
> Effectively, this would even remove the need for CONFIG_USB_MAX_CONTROLLER_COUNT
> at all, since you'd be tracking all the USB controllers in the USB core code and
> in a linked list.

Yeah, right. We won't need the controller count in this case.

>
>> I had plans to add support to use controllers of different types (EHCI
>> and XHCI etc) simultaneously.
>> But haven't really put a code for that yet.
>> Can you suggest some pointers about how would you like to see EHCI and
>> XHCI or even OHCI work
>> together :-)
>> I can take up this.
>
> Thank you, see above please. OHCI might be nastier, but should happen along
> these lines above as well.
Ok, so first i will take up EHCI and XHCI then, and later 'll see the OHCI part.

>
> Best regards,
> Marek Vasut



-- 
Best Regards
Vivek Gautam
Samsung R&D Institute, Bangalore
India