3.7. Test Chip IP¶
Chipyard includes a Test Chip IP library which provides various hardware widgets that may be useful when designing SoCs. This includes a Serial Adapter, Block Device Controller, TileLink SERDES, TileLink Switcher, and UART Adapter.
3.7.1. Serial Adapter¶
The serial adapter is used by tethered test chips to communicate with the host processor. An instance of RISC-V frontend server running on the host CPU can send commands to the serial adapter to read and write data from the memory system. The frontend server uses this functionality to load the test program into memory and to poll for completion of the program. More information on this can be found in Chipyard Boot Process.
3.7.2. Block Device Controller¶
The block device controller provides a generic interface for secondary storage. This device is primarily used in FireSim to interface with a block device software simulation model. The default Linux configuration in firesim-software
To add a block device to your design, add HasPeripheryBlockDevice
to your
lazy module and HasPeripheryBlockDeviceModuleImp
to the implementation.
Then add the WithBlockDevice
config mixin to your configuration.
3.7.3. TileLink SERDES¶
The TileLink SERDES in the Test Chip IP library allow TileLink memory requests to be serialized so that they can be carried off chip through a serial link. The five TileLink channels are multiplexed over two SERDES channels, one in each direction.
There are three different variants provided by the library, TLSerdes
exposes a manager interface to the chip, tunnels A, C, and E channels on
its outbound link, and tunnels B and D channels on its inbound link. TLDesser
exposes a client interface to the chip, tunnels A, C, and E on its inbound link,
and tunnels B and D on its outbound link. Finally, TLSerdesser
exposes
both client and manager interface to the chip and can tunnel all channels in
both directions.
For an example of how to use the SERDES classes, take a look at the
SerdesTest
unit test in the Test Chip IP unit test suite.
3.7.4. TileLink Switcher¶
The TileLink switcher is used when the chip has multiple possible memory interfaces and you would like to select which channels to map your memory requests to at boot time. It exposes a client node, multiple manager nodes, and a select signal. Depending on the setting of the select signal, requests from the client node will be directed to one of the manager nodes. The select signal must be set before any TileLink messages are sent and be kept stable throughout the remainder of operation. It is not safe to change the select signal once TileLink messages have begun sending.
For an example of how to use the switcher, take a look at the SwitcherTest
unit test in the Test Chip IP unit tests.
3.7.5. UART Adapter¶
The UART Adapter is a device that lives in the TestHarness and connects to the
UART port of the DUT to simulate communication over UART (ex. printing out to UART
during Linux boot). In addition to working with stdin/stdout
of the host, it is able to
output a UART log to a particular file using +uartlog=<NAME_OF_FILE>
during simulation.
By default, this UART Adapter is added to all systems within Chipyard by adding the
CanHavePeripheryUARTWithAdapter
and CanHavePeripheryUARTWithAdapterImp
traits to the Top
system.
These traits add a SiFive UART to the system as well as add the UART Adapter to the TestHarness.