In-circuit debugging (#1560)

* openocd script and readme

* do not disable SWD on boot

board/debug/README.md

@@ -0,0 +1,26 @@
+# In-circuit debugging using openocd and gdb
+
+## Hardware
+Connect an ST-Link V2 programmer to the SWD pins on the board. The pins that need to be connected are:
+- GND
+- VTref
+- SWDIO
+- SWCLK
+- NRST
+
+Make sure you're using a genuine one for boards that do not have a 3.3V panda power rail. For example, the tres runs at 1.8V, which is not supported by the clones.
+
+## Openocd
+Install openocd. For Ubuntu 20.04, the one in the package manager works fine: `sudo apt install openocd`.
+
+To run, use `./debug_f4.sh (TODO)` or `./debug_h7.sh` depending on the panda.
+
+## GDB
+You need `gdb-multiarch`.
+
+Once openocd is running, you can connect from gdb as follows:
+```
+$ gdb-multiarch
+(gdb) target ext :3333
+```
+To reset and break, use `monitor reset halt`.

board/debug/debug_h7.sh

@@ -0,0 +1,3 @@
+#!/bin/bash -e
+
+sudo openocd -f "interface/stlink.cfg" -c "transport select hla_swd" -f "target/stm32h7x.cfg" -c "init"

board/stm32h7/stm32h7_config.h

@@ -98,7 +98,7 @@ separate IRQs for RX and TX.
 
 void early_gpio_float(void) {
   RCC->AHB4ENR = RCC_AHB4ENR_GPIOAEN | RCC_AHB4ENR_GPIOBEN | RCC_AHB4ENR_GPIOCEN | RCC_AHB4ENR_GPIODEN | RCC_AHB4ENR_GPIOEEN | RCC_AHB4ENR_GPIOFEN | RCC_AHB4ENR_GPIOGEN | RCC_AHB4ENR_GPIOHEN;
-  GPIOA->MODER = 0; GPIOB->MODER = 0; GPIOC->MODER = 0; GPIOD->MODER = 0; GPIOE->MODER = 0; GPIOF->MODER = 0; GPIOG->MODER = 0; GPIOH->MODER = 0;
+  GPIOA->MODER = 0xAB000000; GPIOB->MODER = 0; GPIOC->MODER = 0; GPIOD->MODER = 0; GPIOE->MODER = 0; GPIOF->MODER = 0; GPIOG->MODER = 0; GPIOH->MODER = 0;
   GPIOA->ODR = 0; GPIOB->ODR = 0; GPIOC->ODR = 0; GPIOD->ODR = 0; GPIOE->ODR = 0; GPIOF->ODR = 0; GPIOG->ODR = 0; GPIOH->ODR = 0;
   GPIOA->PUPDR = 0; GPIOB->PUPDR = 0; GPIOC->PUPDR = 0; GPIOD->PUPDR = 0; GPIOE->PUPDR = 0; GPIOF->PUPDR = 0; GPIOG->PUPDR = 0; GPIOH->PUPDR = 0;
 }