Ar724x.cfg

# Atheros AR724x MIPS 24Kc SoC.
# tested on AP99 refererence board
#
# this settings are taken from source of u-boot for this board
# (for PLL) file:	u-boot/board/ar7240/common/lowlevel_init.S
# (for DDR) file:	u-boot/cpu/mips/ar7240/meminit.c
#      with file:	u-boot/include/configs/ap99.h
# to execute first part of initialization script 
# use this command:	ar724x.cpu invoke-event reset-halt-post
 
adapter_nsrst_delay 100
jtag_ntrst_delay 100
 
reset_config trst_only separate		;# or use only "reset_config none"
#reset_config none
 
set CHIPNAME ar724x
 
jtag newtap $CHIPNAME cpu -irlen 5 -ircapture 0x1 -irmask 0x1f -expected-id 1
 
set TARGETNAME $CHIPNAME.cpu
target create $TARGETNAME mips_m4k -endian big -chain-position $TARGETNAME
 
 
$TARGETNAME configure -event reset-halt-post {
	#reset Watchdog Timer (when timer ends - resets SoC - then again halted)
	mww 0xb806000c 0x400000		;# rst watchdog timer (delay ~250ms for JTAG adapter with slow speed)
	mww 0xb8060008 3		;# rst watchdog timer control (set control bit in this delay window)
 
	sleep 250			;# wait resetting SoC (delay for JTAG adapter with fast speed)
	poll				;# echo target state cpu (must be: running)
	halt
 
	#setup PLL to lowest(default) common denominator 400/400/200 setting
	mww 0xb8050000 0x00090828	;# clr pll mask (rst:02090828)
	mww 0xb8050000 0x00050828	;# CPU:400 DDR:400 AHB:200
	mww 0xb8050000 0x00040828	;# clr pll bypass
 
	#next command will reset for PLL changes to take effect 
	mww 0xb8050008 2		;# set reset_switch
	mww 0xb8050008 3		;# set clock_switch (resets SoC)
}
 
$TARGETNAME configure -event reset-init {
	#complete pll initialization
	mww 0xb8050008 0		;# set reset_switch bit & clock_switch bit
 
	# Setup DDR config and flash mapping
	mww 0xb8000000 0xc7bc8cd0 	;# DDR cfg cdl val (rst:77be8cd0)
	mww 0xb8000004 0x9dd0e6a8 	;# DDR cfg2 cdl val (rst:99d10628)
 
	mww 0xb8000010 8		;# force precharge all banks
	mww 0xb8000008 0x133		;# DDR mode value init
	mww 0xb8000010 1		;# force EMRS update cycle
	mww 0xb800000c 0		;# clr ext. mode register
 
	mww 0xb8000010 2		;# force auto refresh all banks
	mww 0xb8000010 8		;# force precharge all banks
	mww 0xb8000008 0x33		;# set DDR mode value CAS=3
	mww 0xb8000010 1		;# force EMRS update cycle
	mww 0xb8000014 0x4f10		;# DDR refresh value
	mww 0xb8000018 0xff		;# DDR Read Data This Cycle value (16bit: 0xffff)
	mww 0xb800001c 2		;# delay added to the DQS0 line (normal = 7)
	mww 0xb8000020 2		;# delay added to the DQS1 line (normal = 7)
	mww 0xb8000024 0
	mww 0xb8000028 0
}
 
# setup working area somewhere in RAM
$TARGETNAME configure -work-area-phys 0xa0600000 -work-area-size 0x20000
 
# serial SPI capable flash
# flash bank <driver> <base> <size> <chip_width> <bus_width>

Source

http://wiki.openwrt.org/ru/toh/tp-link/tl-mr3420/debrick.using.jtag