LPC1768 updates, IAR board support

Fix some issues with the generic LPC1768 config file:

 - Handle the post-reset clock config:  4 MHz internal RC, no PLL.
   This affects flash and JTAG clocking.

 - Remove JTAG adapter config; they don't all support trst_and_srst

 - Remove the rest of the bogus "reset-init" event handler.

 - Allow explicit CCLK configuration, instead of assuming 12 MHz;
   some boards will use 100 Mhz (or the post-reset 4 MHz).

 - Simplify: rely on defaults for endianness and IR-Capture value

 - Update some comments too

Build on those fixes to make a trivial config for the IAR LPC1768
kickstart board (by Olimex) start working.

Also, add doxygen to the lpc2000 flash driver, primarily to note a
configuration problem with driver: it wrongly assumes the core clock
rate never changes.  Configs that are safe for updating flash after
"reset halt" will thus often be unsafe later ... e.g. for LPC1768,
after switching to use PLL0 at 100 MHz.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

4 files changed, 54 insertions, 26 deletions

diff --git a/NEWS b/NEWS
index 56c697ff..4fef5b2a 100644
--- a/NEWS
+++ b/NEWS
@@ -18,6 +18,7 @@ Flash Layer:
 
 
 Board, Target, and Interface Configuration Scripts:
+	Support IAR LPC1768 kickstart board (by Olimex)
 
 Core Jim/TCL Scripting:
 
diff --git a/src/flash/nor/lpc2000.c b/src/flash/nor/lpc2000.c
index 6674f171..438ab544 100644
--- a/src/flash/nor/lpc2000.c
+++ b/src/flash/nor/lpc2000.c
@@ -33,7 +33,15 @@
 #include <target/armv7m.h>
 
 
-/* flash programming support for NXP LPC17xx and LPC2xxx devices
+/**
+ * @file
+ * flash programming support for NXP LPC17xx and LPC2xxx devices.
+ *
+ * @todo Provide a way to update CCLK after declaring the flash bank.
+ * The value which is correct after chip reset will rarely still work
+ * right after the clocks switch to use the PLL (e.g. 4MHz --> 100 MHz).
+ */
+/*
  * currently supported devices:
  * variant 1 (lpc2000_v1):
  * - 2104 | 5 | 6
diff --git a/tcl/board/iar_lpc1768.cfg b/tcl/board/iar_lpc1768.cfg
new file mode 100644
index 00000000..b8fd026c
--- /dev/null
+++ b/tcl/board/iar_lpc1768.cfg
@@ -0,0 +1,17 @@
+# Board from IAR KickStart Kit for LPC1768
+# See www.iar.com and also
+# http://www.olimex.com/dev/lpc-1766stk.html
+#
+
+source [find target/lpc1768.cfg]
+
+# The chip has just been reset.
+#
+$_TARGETNAME configure -event reset-init {
+	# FIXME update the core clock to run at 100 MHz;
+	# and update JTAG clocking similarly; then
+	# make CCLK match,
+
+	flash probe 0
+}
+
diff --git a/tcl/target/lpc1768.cfg b/tcl/target/lpc1768.cfg
index f0093ad4..182fb89d 100644
--- a/tcl/target/lpc1768.cfg
+++ b/tcl/target/lpc1768.cfg
@@ -1,4 +1,4 @@
-# NXP LPC1768 Cortex-M3 with 512kB Flash and 32kB+32kB Local On-Chip SRAM, clocked with 4MHz internal RC oscillator
+# NXP LPC1768 Cortex-M3 with 512kB Flash and 32kB+32kB Local On-Chip SRAM,
 
 if { [info exists CHIPNAME] } {
 	set  _CHIPNAME $CHIPNAME
@@ -6,12 +6,18 @@ if { [info exists CHIPNAME] } {
 	set  _CHIPNAME lpc1768
 }
 
-if { [info exists ENDIAN] } {
-	set  _ENDIAN $ENDIAN
+# After reset the chip is clocked by the ~4MHz internal RC oscillator.
+# When board-specific code (reset-init handler or device firmware)
+# configures another oscillator and/or PLL0, set CCLK to match; if
+# you don't, then flash erase and write operations may misbehave.
+# (The ROM code doing those updates cares about core clock speed...)
+#
+# CCLK is the core clock frequency in KHz
+if { [info exists CCLK ] } {
+	set _CCLK $CCLK
 } else {
-	set  _ENDIAN little
+	set _CCLK 4000
 }
-
 if { [info exists CPUTAPID ] } {
 	set _CPUTAPID $CPUTAPID
 } else {
@@ -23,29 +29,25 @@ jtag_nsrst_delay 200
 jtag_ntrst_delay 200
 
 # LPC2000 & LPC1700 -> SRST causes TRST
-reset_config trst_and_srst srst_pulls_trst
+reset_config srst_pulls_trst
 
-jtag newtap $_CHIPNAME cpu -irlen 4 -ircapture 0x1 -irmask 0xf -expected-id $_CPUTAPID
+jtag newtap $_CHIPNAME cpu -irlen 4 -expected-id $_CPUTAPID
 
 set _TARGETNAME $_CHIPNAME.cpu
-target create $_TARGETNAME cortex_m3 -endian $_ENDIAN -chain-position $_TARGETNAME
-
-# LPC1768 has 32kB of SRAM on its main system bus (so-called Local On-Chip SRAM)
-$_TARGETNAME configure -work-area-phys 0x10000000 -work-area-size 0x8000 -work-area-backup 0
+target create $_TARGETNAME cortex_m3 -chain-position $_TARGETNAME
 
-# REVISIT is there any good reason to have this reset-init event handler??
-# Normally they should set up (board-specific) clocking then probe the flash...
-$_TARGETNAME configure -event reset-init {
-	# Force NVIC.VTOR to point to flash at 0 ...
-	# WHY?  This is it's reset value; we run right after reset!!
-	mwb 0xE000ED08 0x00
-}
-
-# LPC1768 has 512kB of user-available FLASH (bootloader is located in separate dedicated region).
-# flash bank lpc1700 <base> <size> 0 0 <target#> <variant> <cclk> [calc_checksum]
+# LPC1768 has 32kB of SRAM In the ARMv7-M "Code" area (at 0x10000000)
+# and 32K more on AHB, in the ARMv7-M "SRAM" area, (at 0x2007c000).
+$_TARGETNAME configure -work-area-phys 0x10000000 -work-area-size 0x8000
 
+# LPC1768 has 512kB of flash memory, managed by ROM code (including a
+# boot loader which verifies the flash exception table's checksum).
 set _FLASHNAME $_CHIPNAME.flash
-flash bank $_FLASHNAME lpc2000 0x0 0x80000 0 0 $_TARGETNAME lpc1700 12000 calc_checksum
-
-# 4MHz / 6 = 666kHz, so use 500
-jtag_khz 500
+flash bank $_FLASHNAME lpc2000 0x0 0x80000 0 0 $_TARGETNAME \
+	lpc1700 $_CCLK calc_checksum
+
+# JTAG clock should be CCLK/6 (unless using adaptive clocking)
+# CCLK is 4 MHz after reset, and until board-specific code (like
+# a reset-init handler) speeds it up.
+jtag_rclk [ expr 4000 / 6 ]
+$_TARGETNAME configure -event reset-start { jtag_rclk [ expr 4000 / 6]  }