[openocd] add helper scripts

sw/openocd/README.md

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+## NEORV32 OpenOCD Scripts
+
+* `openocd_neorv32.cfg` For the default **single-core** processor configuration
+* `openocd_neorv32.dual_core.cfg` For the **SMP dual-core** processor configuration
+
+### Helper Scripts
+
+The _helper scripts_ are called by the main OpenOCD configuration files.
+Hence, these scripts are not meant for stand-alone operation.
+
+* `authentication.cfg` Authenticate debug access via the RISC-V DM authentication commands.
+Modify this file (but not the helper procedures) if you are using a
+**custom/non-default authenticator** processor hardware module.
+* `interface.cfg` Physical adapter configuration. Adjust this file to match your specific adapter board.
+* `target.cfg` CPU core(s) and GDB configuration. This file should not be altered.

sw/openocd/authentication.cfg

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+# -------------------------------------------------------------------
+# Authenticator helper functions. Do not edit.
+# -------------------------------------------------------------------
+
+# write 32-bit data word to authenticator data input
+proc authenticator_write {WDATA} {
+  riscv authdata_write $WDATA
+}
+
+# read 32-bit data word from authenticator data output
+proc authenticator_read {} {
+  return [riscv authdata_read]
+}
+
+# check if authentication was successful (bit 7 in dmstatus)
+proc authenticator_check {} {
+  set DMSTATUS [riscv dmi_read 0x11]
+  if { [expr {$DMSTATUS & (1<<7)}] } {
+    echo "Authentication passed."
+  } else {
+    echo "AUTHENTICATION FAILED!"
+    exit
+  }
+}
+
+# ---------------------------------------------------------
+# Authentication process.
+# Adjust this for your custom/non-default authenticator.
+# ---------------------------------------------------------
+# read challenge
+set CHALLENGE [authenticator_read]
+# compute response (default authenticator module)
+set RESPONSE [expr {$CHALLENGE | 1}]
+# send response
+authenticator_write $RESPONSE
+# success?
+authenticator_check

sw/openocd/interface.cfg

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+# -------------------------------------------------------------------
+# Physical interface configuration.
+# Adjust this file for your specific debug adapter.
+# -------------------------------------------------------------------
+adapter driver ftdi
+ftdi vid_pid 0x0403 0x6010
+ftdi channel 0
+ftdi layout_init 0x0038 0x003b
+adapter speed 4000
+transport select jtag

sw/openocd/target.cfg

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+# -------------------------------------------------------------------
+# Target configuration and (session) initialization
+# Do not edits this file.
+# -------------------------------------------------------------------
+proc target_setup { {NUM_CORES 1} } {
+
+  # path of this file
+  set PATH [ file dirname [ file normalize [ info script ] ] ]
+
+  # configure physical interface
+  source [file join $PATH interface.cfg]
+
+  set CORENAME neorv32
+
+  # configures JTAG tap
+  jtag newtap $CORENAME cpu -irlen 5
+
+  # attach core(s)
+  if { $NUM_CORES == 1 } {
+    set TARGETNAME $CORENAME.cpu
+    target create $TARGETNAME riscv -chain-position $TARGETNAME
+  } elseif { $NUM_CORES == 2 } {
+    set TARGETNAME_0 $CORENAME.cpu0
+    set TARGETNAME_1 $CORENAME.cpu1
+    target create $TARGETNAME_0 riscv -chain-position $CORENAME.cpu -rtos hwthread
+    target create $TARGETNAME_1 riscv -chain-position $CORENAME.cpu -coreid 1
+    target smp $TARGETNAME_0 $TARGETNAME_1
+  } else {
+    echo "ERROR: Invalid NUM_CORE configuration!"
+  }
+
+  # GDB server configuration
+  gdb report_data_abort enable
+  gdb report_register_access_error enable
+
+  # expose additional / NEORV32-specific CSRs
+  riscv expose_csrs 2048=cfureg0
+  riscv expose_csrs 2049=cfureg1
+  riscv expose_csrs 2050=cfureg2
+  riscv expose_csrs 2051=cfureg3
+  riscv expose_csrs 4032=mxisa
+
+  # initialize target
+  init
+
+  # authenticate
+  source [file join $PATH authentication.cfg]
+
+  # halt
+  halt
+  echo "Target HALTED. Ready for remote connections."
+}