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

[Bin Liu]

On 10/14/2015 10:56 AM, Felipe Balbi wrote:

Hi,

Bin Liu <b-...@ti.com> writes:

Hi,

On 10/13/2015 01:22 PM, Felipe Balbi wrote:

Yegor Yefremov <yegorsli...@googlemail.com> writes:

On Mon, Oct 12, 2015 at 11:34 AM, Yegor Yefremov
<yegorsli...@googlemail.com> 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.

MUSB does not support dynamic EP allocation for INT/ISOCH.
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