CSR access widths can be different from register widths. 8-bit
registers are common.
The runtime-generated `read()` and `write()` functions handle this
mapping correctly. When direct register accesses are handled, this
mapping is lost.
Use the accessor functions rather than directly accessing the memory
addresses, so that we work on platforms other than 32-bit-wide.
Signed-off-by: Sean Cross <sean@xobs.io>
The REFRESH register accepts an 8-bit address and determines which
register to refresh. Since there are only two addresses currently in
use, this register can be either 0x00 or 0x04.
A refactor replaced the compare with one that checked for any 0 bits.
Since both 0x00 and 0x04 have 0 bits, this check always evaluated as
true, causing the logic to always refresh the CORE register.
Replace this check with an explicit check for 0x00.
Signed-off-by: Sean Cross <sean@xobs.io>
Add the vexriscv_debug program to the list of scripts created when
installing this module. This program is a simple bridge that allows
openocd to talk to the vexriscv core so it can be debugged.
Signed-off-by: Sean Cross <sean@xobs.io>
Enable resetting the UART by adding a ResetInserter to the UART.
The UART must be reset when resetting the softcore.
Signed-off-by: Sean Cross <sean@xobs.io>
Allow a new cpu_debugging flag to be passed to the constructor to
enable in-circuit live debugging of the softcore under gdb.
Signed-off-by: Sean Cross <sean@xobs.io>
Add support for debugging the CPU, and gate it behind a new cpu_debug
parameter. With this enabled, a simple Wishbone interface is provided.
The debug version of the core adds two 32-bit registers to the CPU.
The register at address 0 indicates status, and is used to halt
and reset the core.
The debug register at address 4 is used to inject opcodes into the
core, and read back the result.
A patched version of OpenOCD can be used to attach to this bus via
the Litex Ethernet or UART bridges.
Signed-off-by: Sean Cross <sean@xobs.io>
The upstream vexriscv repo now generates both the current VexRiscv.v
softcore, as well as VexRiscv-Debug.v. This -Debug varient exposes
their specialized debug bus that allows for attaching a modified version
of openocd.
Sync the litex repo with the upstream version to take advantage of debug
support.
Signed-off-by: Sean Cross <sean@xobs.io>
The BIOS builds just fine on Windows, but afterwards tries to run
`chmod`. This command does not exist on Windows, and is unnecessary.
Add a conditional guard to prevent this command from running on Windows.
Signed-off-by: Sean Cross <sean@xobs.io>
Florent Kermarrec
Sean Cross