Re: musb: communication issue with more than 12 FTDI ports

[Felipe Balbi <balbi-l0cyMroinI0@public.gmane.org>]

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Hi,

Bin Liu <b-liu-l0cyMroinI0@public.gmane.org> writes:
> Hi,
>
> On 10/13/2015 01:22 PM, Felipe Balbi wrote:
>> Yegor Yefremov <yegorslists-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> writes:
>>> On Mon, Oct 12, 2015 at 11:34 AM, Yegor Yefremov
>>> <yegorslists-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote:
>>>> We have a problem, when using more than 12 FTDI ports. Kernels tried:
>>>> 3.18.1, 4.2.3 and 4.3-rc5. SoC am335x 600MHz
>>>>
>>>> Below the USB topology:
>>>>
>>>> # lsusb -t
>>>> /:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=musb-hdrc/1p, 480M
>>>> /:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=musb-hdrc/1p, 480M
>>>>      |__ Port 1: Dev 2, If 0, Class=, Driver=hub/4p, 480M
>>>>          |__ Port 1: Dev 9, If 0, Class=, Driver=hub/4p, 480M
>>>>              |__ Port 1: Dev 10, If 0, Class=, Driver=ftdi_sio, 12M
>>>>              |__ Port 2: Dev 11, If 0, Class=, Driver=ftdi_sio, 480M
>>>>              |__ Port 2: Dev 11, If 1, Class=, Driver=ftdi_sio, 480M
>>>>              |__ Port 2: Dev 11, If 2, Class=, Driver=ftdi_sio, 480M
>>>>              |__ Port 2: Dev 11, If 3, Class=, Driver=ftdi_sio, 480M
>>>>              |__ Port 3: Dev 12, If 0, Class=, Driver=ftdi_sio, 480M
>>>>              |__ Port 3: Dev 12, If 1, Class=, Driver=ftdi_sio, 480M
>>>>              |__ Port 3: Dev 12, If 2, Class=, Driver=ftdi_sio, 480M
>>>>              |__ Port 3: Dev 12, If 3, Class=, Driver=ftdi_sio, 480M
>>>>          |__ Port 2: Dev 4, If 0, Class=, Driver=ftdi_sio, 480M
>>>>          |__ Port 2: Dev 4, If 1, Class=, Driver=ftdi_sio, 480M
>>>>          |__ Port 2: Dev 4, If 2, Class=, Driver=ftdi_sio, 480M
>>>>          |__ Port 2: Dev 4, If 3, Class=, Driver=ftdi_sio, 480M
>>>>          |__ Port 3: Dev 7, If 0, Class=, Driver=ftdi_sio, 480M
>>>>          |__ Port 3: Dev 7, If 1, Class=, Driver=ftdi_sio, 480M
>>>>          |__ Port 3: Dev 7, If 2, Class=, Driver=ftdi_sio, 480M
>>>>          |__ Port 3: Dev 7, If 3, Class=, Driver=ftdi_sio, 480M
>
> How many EPs does each FTDI device require? at least one INT EP, right? 
> If I read it right, the topology above has 2 hubs, and 16 high-speed 
> FTDI and 1 full-speed FTDI. So it requires at least 18 high-speed INT 
> EPs. MUSB driver only has 11 high-speed EPs for mode-4 which is the EP 
> configuration used by default. I am wondering how those devices got 
> enumerated properly.

dynamic EP allocation, but that has its own limitations.

-- 
balbi

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