[U-Boot] [PATCH 10/16] usb: xhci: Program 'route string' in the input slot context

[Marek Vasut]

On 06/27/2017 07:23 AM, Stefan Roese wrote:
> Hi Bin,
> 
> On 27.06.2017 02:01, Bin Meng wrote:
>> On Tue, Jun 27, 2017 at 2:07 AM, Marek Vasut <marex at denx.de> wrote:
>>> On 06/24/2017 03:57 AM, Bin Meng wrote:
>>>> Hi Marek,
>>>>
>>>> On Sat, Jun 24, 2017 at 2:02 AM, Marek Vasut <marex at denx.de> wrote:
>>>>> On 06/23/2017 11:54 AM, Bin Meng wrote:
>>>>>> xHCI spec says: the values of the 'route string' field shall be
>>>>>> initialized by the first 'Address Device' command issued to a
>>>>>> device slot, and shall not be modified by any other command.
>>>>>>
>>>>>> So far U-Boot does not program this field, and it does not prevent
>>>>>> SS device directly attached to root port, or HS device behind an HS
>>>>>> hub, from working, due to the fact that 'route string' is used by
>>>>>> the xHC to target SS packets. But in order to enumerate devices
>>>>>> behind an SS hub, this field must be programmed.
>>>>>>
>>>>>> With this commit and along with previous commits, now SS & HS devices
>>>>>> attached to a USB 3.0 hub can be enumerated by U-Boot.
>>>>>>
>>>>>> As usual, this new feature is only available when DM is on.
>>>>>
>>>>> Great, but I really dislike the ifdef pollution, so this needs to be
>>>>> sorted out.
>>>>
>>>> The ifdef was needed due to it calls DM APIs or access DM udevice. I
>>>> have no intention to add a new feature to the non-DM driver.
>>>
>>> But then this creates a massive disparity, it's like we're growing two
>>> USB stacks.
>>>
>>
>> Yep, unfortunately. But if we continue adding new features/fixes to
>> the old non-DM stuff, I am not sure how this can encourage people to
>> switch to DM.
> 
> Correct. We definitely don't want to add new features to non-DM
> drivers / IF, if this is non-trivial.

Fine, but we also don't want to grow two distinct stacks with a boatload
of ifdefs all over the place. That's a nightmare to maintain.
I think I mentioned that already, but I'd be far more accepting to this
solution if we could at least keep the added ifdefs to minimum and
somehow keep them in one place instead of adding them all over the code.

>> Maybe I can check all boards that use xHCI to see if
>> they are switched to DM?
> 
> xHCI is still quite new in U-Boot, so I would expect that all
> platforms using it, are using DM or at least not far away from using
> it. Yes, please check all xHCI "users", if they use DM. Then we
> know if and which users need some "persuasion" to switch over to
> DM soon. ;)
> 
> Thanks,
> Stefan


-- 
Best regards,
Marek Vasut