Description

A Nios II hardware design can include one or more triple speed ethernet devices or TSEs. The package CYGPKG_DEVS_ETH_NIOS2_TSE provides an eCos driver for a single TSE device. It supports both polled mode for use by RedBoot and interrupt-driven mode for use by a full TCP/IP stack.

Configuration Options

The Nios II TSE driver package should be loaded automatically when creating an eCos configuration for a hardware design which includes the required devices, and it should never be necessary to load the package explicitly. If the application does not actually require ethernet functionality then the package is inactive and the final executable will not suffer any overheads from unused functionality. This is determined by the presence of the generic ethernet I/O package CYGPKG_IO_ETH_DRIVERS. Typically the choice of eCos template causes the right thing to happen. For example the default template does not include any TCP/IP stack so CYGPKG_IO_ETH_DRIVERS is not included, but both the net and redboot templates do include a TCP/IP stack so will specify that package and hence enable the ethernet driver.

The driver package will only instantiate the support for a single TSE device. If the hardware design involves multiple TSE devices then support for the additional ones can be instantiated by application code. This can be achieved largely by cloning file src/tse0.c in this package.

There are two configuration options related to the device instantiation. CYGDAT_DEVS_ETH_NIOS2_TSE0_NAME sets the device name, defaulting to “eth0”. Typically this only needs to be changed if the hardware design includes other types of ethernet device and their drivers also attempt to create a device “eth0”. CYGDAT_DEVS_ETH_NIOS2_TSE_ETH0_MAC specifies the fallback ethernet station address or MAC address. In typical eCos systems the MAC address is provided via a RedBoot fconfig option, allowing each board to have its own address. However if the fconfig functionality is unavailable, for example when debugging via jtag, then the fallback address will be used instead. Note that each board on a network must have a unique MAC address, so if there are several boards on the network using the fallback address and the same eCos configuration then network communication can be expected to fail. Applications can also change the MAC address at run-time using a SIOCSIFHWADDR ioctl. However this ioctl should not be used when debugging over ethernet because it will break the debug channel.

Porting

Each triple speed ethernet device requires three units in the hardware design: the tse_mac unit itself, and sgdma_rx and sgdma_tx scatter-gather DMA controllers. Typically the hardware design will also include a bank of on-chip RAM to hold the DMA descriptors. The settings for these units are best cloned from a reference hardware design such as the TSE_SGDMA examples in the Nios II Embedded Design Suite, or the eCosPro_TSEplus design. The h/w design HAL package should provide address and interrupt vector definitions for the various units.