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
When using 12 ports and performing serial test (a pair of ports is
connected via null-modem cable and a rather short string ca. 90
characters will be sent alternating at 1200 and 115200b/s, testing
scripts are written in Python and running as own processes per a pair
of ports) there are no timeouts, i.e. all sent characters will be
received. As soon as I open ports 13 and 14 I start to get arbitrary
timeouts (from test software point of view) on all ports.
In order to check, if ftdi_sio has primary to do with this issue, I've
performed the same test on a PC and PandaBoard Rev. A2 (EHCI port) and
there were no issues with 16 ports. So it seems to have something to
do with am335x + musb + number of end points.
Any idea? Let me know, if you need our test script.
Yegor
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