tcl/target: add initial Bouffalo Lab BL702 chip series support

Adds initial support for the BL702 series of chips, BL702, BL704 and BL706.
No flash bank support yet.

File name bl702.tcl was chosen over bl70x.tcl, because Bouffalo Lab
uses bl702 to mark the whole series in many of their tools.

The ndmreset bit in the RISC-V Debug Module isn't implemented correctly,
so it doesn't trigger a system reset as it should.
To solve this problem, the software reset is implemented
in the reset-assert-pre hook, which uses best reset method I could find.
What is not reset is the GLB core, which handles GPIOs, pinmux, etc.
The reset mechanism has been extensively tested, and works correctly
for both "reset run" and "reset halt", which the latter
halts very early in the BootROM.

Change-Id: I5ced6eb3902d1b9d9c1bba56f817ec5dc3493cb0
Signed-off-by: Marek Kraus <gamelaster@outlook.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/8407
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

tcl/target/bl702.cfg

@@ -0,0 +1,60 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+#
+# Bouffalo Labs BL702, BL704 and BL706 target
+#
+# https://en.bouffalolab.com/product/?type=detail&id=8
+#
+# Default JTAG pins: (if not changed by eFuse configuration)
+# TMS - GPIO0
+# TDI - GPIO1
+# TCK - GPIO2
+# TDO - GPIO9
+#
+
+source [find mem_helper.tcl]
+
+transport select jtag
+
+if { [info exists CHIPNAME] } {
+	set _CHIPNAME $CHIPNAME
+} else {
+	set _CHIPNAME bl702
+}
+
+jtag newtap $_CHIPNAME cpu -irlen 5 -expected-id 0x20000e05
+
+set _TARGETNAME $_CHIPNAME.cpu
+target create $_TARGETNAME riscv -chain-position $_TARGETNAME
+
+riscv set_mem_access sysbus
+
+$_TARGETNAME configure -work-area-phys 0x22020000 -work-area-size 0x10000 -work-area-backup 1
+
+# Internal RC ticks on 32 MHz, so this speed should be safe to use.
+adapter speed 4000
+
+$_TARGETNAME configure -event reset-assert-pre {
+	halt
+
+	# Switch clock to internal RC32M
+	# In HBN_GLB, set ROOT_CLK_SEL = 0
+	mmw 0x4000f030 0x0 0x00000003
+	# Wait for clock switch
+	sleep 10
+
+	# GLB_REG_BCLK_DIS_FALSE
+	mww 0x40000ffc 0x0
+
+	# HCLK is RC32M, so BCLK/HCLK doesn't need divider
+	# In GLB_CLK_CFG0, set BCLK_DIV = 0 and HCLK_DIV = 0
+	mmw 0x40000000 0x0 0x00FFFF00
+	# Wait for clock to stabilize
+	sleep 10
+
+	# Do reset
+	# In GLB_SWRST_CFG2, clear CTRL_SYS_RESET, CTRL_CPU_RESET and CTRL_PWRON_RESET
+	mmw 0x40000018 0x0 0x00000007
+	# In GLB_SWRST_CFG2, set CTRL_SYS_RESET, CTRL_CPU_RESET and CTRL_PWRON_RESET to 1
+	mmw 0x40000018 0x6 0x0
+}