From 5f6ad0ae7eb147e3d5f022bbffd55eb4a46f2e41 Mon Sep 17 00:00:00 2001
From: Berkus Decker <berkus+github@metta.systems>
Date: Sun, 3 Feb 2019 11:49:17 +0200
Subject: [PATCH] Finally working jtag config!

---
 doc/rpi3_interface.cfg |  3 +-
 doc/rpi3_jtag.md       | 73 ++++++------------------------------------
 doc/rpi3_target.cfg    |  8 ++---
 3 files changed, 14 insertions(+), 70 deletions(-)

diff --git a/doc/rpi3_interface.cfg b/doc/rpi3_interface.cfg
index 42e3e80..1cb0bcd 100644
--- a/doc/rpi3_interface.cfg
+++ b/doc/rpi3_interface.cfg
@@ -7,7 +7,7 @@ bcm2835gpio_peripheral_base 0x3F000000
 # Transition delay calculation: SPEED_COEFF/khz - SPEED_OFFSET
 # These depend on system clock, calibrated for stock 700MHz
 # bcm2835gpio_speed SPEED_COEFF SPEED_OFFSET
-bcm2835gpio_speed_coeffs 146203 36
+bcm2835gpio_speed_coeffs 194938 48
 
 # Each of the JTAG lines need a gpio number set: tck tms tdi tdo
 # Header pin numbers: 23 22 19 21
@@ -17,4 +17,3 @@ bcm2835gpio_jtag_nums 11 25 10 9
 # Header pin numbers: TRST - 26, SRST - 12
 
 bcm2835gpio_trst_num 7
-reset_config trst_only
diff --git a/doc/rpi3_jtag.md b/doc/rpi3_jtag.md
index 575c9a3..6ef5306 100644
--- a/doc/rpi3_jtag.md
+++ b/doc/rpi3_jtag.md
@@ -38,22 +38,22 @@ FUNC  |  GPIO  |  PIN #  |  MODE
 ------+--------+---------+------
 TCK   | GPIO25 |   22    | Alt4
 TMS   | GPIO27 |   13    | Alt4
-TDI   | GPIO4  |    7    | Alt5
+TDI   | GPIO26 |   37    | Alt4
 TDO   | GPIO24 |   18    | Alt4
 TRST  | GPIO22 |   15    | Alt4
 GND   | GND    |   20    |
 ```
 
+Connecting TDI to pin 7 (GPIO4) did not work!
+
 In config.txt:
 
 ```
 # Set GPIO pins for JTAG debugger connection on rpi3
-gpio=22-25,27=a4
-gpio=4=a5
-# gpio23 RTCK - unused? Don't forget to avoid frequency scaling in this case.
+gpio=22-27=a4
 ```
 
-Alternatively, just specify
+Alternatively, just specify @todo - verify this works with all alt4 pins
 
 ```
 enable_jtag_gpio=1
@@ -66,7 +66,7 @@ Func | Host Pin | Wire color | Target pin
 -----+----------+------------+-----------
 TCK  |    23    |   yellow   |    22
 TMS  |    22    |   brown    |    13
-TDI  |    19    |   green    |     7
+TDI  |    19    |   green    |    37
 TDO  |    21    |   orange   |    18
 TRST |    26    |    red     |    15
 GND  |    20    |   black    |    20
@@ -77,66 +77,11 @@ GND  |    20    |   black    |    20
 
 You need two files: interface file for driving the host GPIO correctly, and target file for detecting the JTAG circuitry on the target RPi.
 
-Interface configuration: rpi3_interface.cfg
+Interface configuration: [rpi3_interface.cfg](./rpi3_interface.cfg)
 
-```
-# Broadcom 2835 on Raspberry Pi as JTAG host
+[Source](https://movr0.com/2016/09/02/use-raspberry-pi-23-as-a-jtagswd-adapter/), [source #2 - rpi3 speed_coeffs](https://forum.doozan.com/read.php?3,21789)
 
-interface bcm2835gpio
- 
-bcm2835gpio_peripheral_base 0x3F000000
- 
-# Transition delay calculation: SPEED_COEFF/khz - SPEED_OFFSET
-# These depend on system clock, calibrated for stock 700MHz
-# bcm2835gpio_speed SPEED_COEFF SPEED_OFFSET
-bcm2835gpio_speed_coeffs 146203 36
- 
-# Each of the JTAG lines need a gpio number set: tck tms tdi tdo
-# Header pin numbers: 23 22 19 21
-bcm2835gpio_jtag_nums 11 25 10 9
- 
-# If you define trst or srst, use appropriate reset_config
-# Header pin numbers: TRST - 26, SRST - 12
- 
-bcm2835gpio_trst_num 7
-reset_config trst_only
-```
-
-[Source](https://movr0.com/2016/09/02/use-raspberry-pi-23-as-a-jtagswd-adapter/)
-
-
-* @todo Find out about bcm2835gpio_speed_coeffs
-
-
-Target configuration: rpi3_target.cfg
-
-```
-# Broadcom 2835 on Raspberry Pi as JTAG target
-
-telnet_port 4444
-gdb_port 5555
-
-adapter_khz 1000
-transport select jtag
-
-if { [info exists CHIPNAME] } {
-set _CHIPNAME $CHIPNAME
-} else {
-set _CHIPNAME rspi
-}
- 
-if { [info exists CPU_TAPID ] } {
-set _CPU_TAPID $CPU_TAPID
-} else {
-set _CPU_TAPID 0x07b7617F
-}
- 
-jtag newtap $_CHIPNAME arm -irlen 5 -expected-id $_CPU_TAPID
- 
-set _TARGETNAME $_CHIPNAME.arm
-target create $_TARGETNAME arm11 -chain-position $_TARGETNAME
-$_TARGETNAME configure -event gdb-attach { halt }
-```
+Target configuration: [rpi3_target.cfg](./rpi3_target.cfg)
 
 [Source #1](https://electronics.stackexchange.com/questions/249008/how-to-use-rpi-2-to-debug-rpi-model-b-via-jtag-with-openocd/419724#419724), [source #2](https://sysprogs.com/tutorials/preparing-raspberry-pi-for-jtag-debugging/), [source #3](http://openocd.org/doc/html/Reset-Configuration.html), [source #4](http://infocenter.arm.com/help/topic/com.arm.doc.faqs/ka3854.html), [source #5](https://www.raspberrypi.org/forums/viewtopic.php?p=1013802), [source #6 - proper rpi3 ocd config](https://www.suse.com/c/debugging-raspberry-pi-3-with-jtag/), [source #7 - simpler rpi3 ocd config](https://github.com/daniel-k/openocd/blob/armv8/tcl/target/rpi3.cfg), [source #8 - explanations about SRST](https://catch22.eu/baremetal/openocd_sysfs_stm32/)
 
diff --git a/doc/rpi3_target.cfg b/doc/rpi3_target.cfg
index 7fd2254..6225e33 100644
--- a/doc/rpi3_target.cfg
+++ b/doc/rpi3_target.cfg
@@ -6,11 +6,11 @@ gdb_port 5555
 
 transport select jtag
 
-# we need to enable srst even though we don't connect it
-reset_config trst_and_srst
+reset_config trst_only
 
-adapter_khz 1000
-jtag_ntrst_delay 500
+adapter_khz 500
+adapter_nsrst_delay 100
+jtag_ntrst_delay 100
 
 if { [info exists CHIPNAME] } {
     set _CHIPNAME $CHIPNAME