Virtual Serial Ports
We have created a patch for SCC Linux and the crbif driver (running on the MCPC) that provides virtual serial ports to each SCC core. You can download it here:
|Patches compatible with sccKit 1.3.0 (marcbug svn rev 153)|
|Linux (no serial console)||linux153_vuart_noconsole.diff|
|Linux (with serial console)||linux153_vuart_console.diff|
|Linux (command line for serial console)||linux153_vuart_console_cmd.bin|
|crbif 1.1.3 (complete)||crbif-dkms-1.1.3-tty.tar.bz2|
The patched crbif driver emulates 4 standard 16550A UARTs on default I/O addresses (0x3f8, 0x2f8, 0x3e8, 0x2e8), independent for each SCC core (192 devices total). These UARTs are connected to corresponding character devices on the MCPC, similar to a real setup of two machines connected by a null-modem cable. Standard programs for accessing serial ports (like minicom) can be used on the MCPC to exchange data with SCC cores.
Using our virtual serial ports requires recompiling both the crbif driver and SCC Linux. Currently, only the versions compatible with sccKit 1.3.0 are supported. We kindly ask users of newer versions to wait until corresponding sources are published, so we have a chance to change our patches accordingly.
You need to install modified versions of both the crbif driver and SCC Linux for the serial ports to work.
Recompiling crbif.ko with UART supportTo create the modified driver, follow these steps:
- Checkout the crbif sources that are compatible to the patch
file. For example, crbif153_vuart.diff (the patch file for
revision 153 of crbif from sccKit 1.3.0) can be used with the
sources at revision 153 from the marcbug svn. Therefore, to check
out these sources, use the following command:
# svn checkout http://marcbug.scc-dc.com/svn/repository/trunk/mcpc_driver@153
- Place the patch file in the
mcpc_driverdirectory, then apply it as follows:
# cd mcpc_driver
# patch -u -i crbif153_vuart.diff
- Compile the driver:
# make crbif.ko
Before you can load the new driver, you need to close sccKit or any other program that accesses /dev/crbif0rb0. Afterwards, issue the following commands:
# sudo rmmod crbif
# sudo insmod crbif.ko
You may also choose to replace the Intel-provided crbif driver with
the recompiled one, thus allowing it to get loaded automatically
after booting the MCPC. To do so, replace the corresponding binary
under /var/lib/dkms/crbif-dkms/. For example, if you are
using driver version 1.1.0 on an x86-64 MCPC with Linux kernel
release 2.6.36-rc8-edac-2 (as returned by
you will find the driver binary in
Building SCC Linux with UART supportWe provide two patches for SCC Linux, depending on whether you need support for a root console via the serial port. When using the *_noconsole.diff patch, each core gets 4 serial ports, but none of them will function as a root console. In contrast, the *_console.diff patch also provides 4 serial ports, but opens a root console on the first one.
- Download SCC Linux sources as described in the document How to build SCC Linux on the MARC website.
- Place the patch file corresponding to the SVN revision into the
sandboxdirectory, then apply the patch by executing a command like
patch -u -i linux153_vuart_noconsole.diff.
- If you used the *_console.diff patch, replace the file
linuxkernel/images/commandline.binby the corresponding modified one (e.g.,
linux153_vuart_console_cmd.binfor SVN revision 153).
- Build the Linux image as described in How to build SCC Linux.
Using serial ports
When starting the modified SCC Linux while the patched crbif driver is loaded on the MCPC, each core recognizes four serial ports. All 192 ports are independently connected to character devices on the MCPC.
Serial ports on SCC cores use the names
/dev/ttyS3, corresponding virtual devices on the MCPC
use names like
/dev/crbif0rb0c0ttyS0. The number after
crbif0rb0c specifies the target SCC core, the remainder
of the name is identical to the device name from SCC Linux. For
/dev/ttyS1 (DOS name COM2) of SCC core 30 is
connected to the device
/dev/crbif0rb0c30ttyS1 on the
Devices on both SCC Linux and the MCPC can be used just like real
hardware serial ports; e.g., input and output streams of programs
can be redirected to them. To write the list of files in the root
directory to the serial port, you can use the command
-lisa > /dev/ttyS0 on an SCC Linux core. If you have
cat /dev/crbif0rb0c0ttyS0 running on the MCPC, it will
receive the data sent to the port (this example is for core 0).
Please note that we currently simulate a null-modem connection without flow control, so data may be lost if the receiving side is too slow in reading from its port. However, we never experienced this during our experiments.