🐛 fix bug in crt0.S interrupt setup (#297)

* 🐛 fixed crt0 IRQ setup

The first thing crt0 has t do is to disable interrupts globally!

* update executable images

due to chnage of crt0.S

* add version 1.6.9.11

* add crt0 IRQ disable to docs

CHANGELOG.md

@@ -33,6 +33,7 @@ The version number is globally defined by the `hw_version_c` constant in the mai
 
 | Date (*dd.mm.yyyy*) | Version | Comment |
 |:----------:|:-------:|:--------|
+| 08.04.2022 | 1.6.9.11 | :bug: fixed bug in interrupt setup of **`crt0` start-up code** [#297](https://github.com/stnolting/neorv32/pull/297) |
 | 08.04.2022 | 1.6.9.10 | rework compressed instruction (`C` ISA extension) de-compressor: :lock: closed further illegal compressed instruction holes; code clean-ups; `mtval` CSR now shows the decompressed 32-bit instruction when executing an illegal compressed instruction; minor RTL code cleanups (removing legacy stuff); [PR #296](https://github.com/stnolting/neorv32/pull/296) |
 | 07.04.2022 | 1.6.9.9 | AND-gate CSR read address: reduces **CPU switching activity** (= dynamic power consumption) and even reduces area costs; [PR #295](https://github.com/stnolting/neorv32/pull/295) |
 | 06.04.2022 | 1.6.9.8 | :bug: fixed instruction decoding collision in CPU `B` extension; :lock: closed further illegal instruction encoding holes; optimized illegal instruction detection logic; [PR #294](https://github.com/stnolting/neorv32/pull/294) |

docs/datasheet/software.adoc

@@ -445,11 +445,12 @@ and placed right before the actual application code so it gets executed right af
 The `crt0.S` start-up performs the following operations:
 
 [start=1]
+. Disable interrupts globally by clearing <<_mstatus>>`.mie`.
 . Initialize all integer registers `x1 - x31` (or just `x1 - x15` when using the `E` CPU extension) to a defined value.
-. Initialize the global pointer `gp` and the stack pointer `sp` according to the <<_ram_layout>> provided by the linker script.
 . Initialize all CPU core CSRs and also install a default "dummy" trap handler for _all_ traps. This handler catches all traps
+** All interrupt sources are disabled and all pending interrupts are cleared.
+. Initialize the global pointer `gp` and the stack pointer `sp` according to the <<_ram_layout>> provided by the linker script.
 during the early boot phase.
-. All interrupt sources are disabled and all pending interrupts are cleared.
 . Clear all counter CSRs and stop auto-increment.
 . Clear IO area: Write zero to all memory-mapped registers within the IO region (`iodev` section). If certain devices have not
 been implemented, a bus access fault exception will occur. This exception is captured by the dummy trap handler.

docs/userguide/debugging_with_ocd.adoc

@@ -175,6 +175,13 @@ After the upload, GDB will make the processor jump to the beginning of the uploa
 (by default, this is the beginning of the instruction memory at `0x00000000`) skipping the bootloader
 and halting the CPU right before executing the `blink_led` application.
 
+[IMPORTANT]
+After gdb has connected to the CPU, it is recommended to disable the CPU's global interrupt flag
+(`mstatus.mie`, = bit #3) to prevent unintended calls of potentially outdated trap handlers. The global
+interrupt flag can be cleared using the following gdb command:
+`set $mstatus = ($mstatus & ~(1<<3))`. Interrupts can be enabled globally again by the following command:
+`set $mstatus = ($mstatus | (1<<3))`.
+
 
 :sectnums:
 ==== Software Breakpoints

rtl/core/neorv32_bootloader_image.vhd

@@ -11,7 +11,7 @@ use neorv32.neorv32_package.all;
 package neorv32_bootloader_image is
 
   constant bootloader_init_image : mem32_t := (
-    00000000 => x"00000037",
+    00000000 => x"30047073",
     00000001 => x"80010117",
     00000002 => x"1f810113",
     00000003 => x"80010197",
@@ -867,7 +867,7 @@ package neorv32_bootloader_image is
     00000853 => x"444c420a",
     00000854 => x"41203a56",
     00000855 => x"20207270",
-    00000856 => x"30322036",
+    00000856 => x"30322038",
     00000857 => x"480a3232",
     00000858 => x"203a5657",
     00000859 => x"00000020",

rtl/core/neorv32_package.vhd

@@ -65,7 +65,7 @@ package neorv32_package is
   -- Architecture Constants (do not modify!) ------------------------------------------------
   -- -------------------------------------------------------------------------------------------
   constant data_width_c : natural := 32; -- native data path width - do not change!
-  constant hw_version_c : std_ulogic_vector(31 downto 0) := x"01060910"; -- NEORV32 version - no touchy!
+  constant hw_version_c : std_ulogic_vector(31 downto 0) := x"01060911"; -- NEORV32 version - no touchy!
   constant archid_c     : natural := 19; -- official NEORV32 architecture ID - hands off!
 
   -- Check if we're inside the Matrix -------------------------------------------------------

sw/common/crt0.S

@@ -47,8 +47,13 @@ _start:
 // ************************************************************************************************
 // This is the very first instruction that is executed after hardware reset. It ensures that x0 is
 // written at least once - the CPU HW will ensure it is always set to zero on any write access.
+//
+// Furthermore, we have to disable ALL interrupts, which is required if this code is part of a
+// program uploaded by the on-chip debugger (potentionally taking control from the bootloader).
+// We setup a new stack pointer here and WE DO NOT WANT TO trap to an outdated trap handler with
+// a modified stack pointer.
 // ************************************************************************************************
-  lui zero, 0 // "dummy" instruction that uses no reg-file input operands at all
+  csrrci zero, mstatus, (1<<3) // disable global interrupt flag and write "anything" to x0
 
 
 // ************************************************************************************************