Amiga, serial and SYSRQ

Paolo Pisati
2024-05-18T18:17:53Z

Hi,

what's the key sequence to trigger SYSRQ on Amiga? And what's the sequence if
i'm redirecting the console via serial?

Some context: i'm trying to collect a backtrace from my Amiga 1200 + Warp
1260[1] + flicker fixer that refuses to boot and shows a solid grey screen.

By using a serial, i've seen it booting up to:

ABCDGHIJK
Linux version 6.6.30-amiga-00006-g809aa9a54cba (flag@amaterasu.local) (m68k-linux-gcc (GCC) 13.1.0, GNU ld (GNU Binutils) 4
Saving 454 bytes of bootinfo
printk: console [debug0] enabled
printk: Too late to register bootconsole debug-1
Amiga hardware found: [A1200] VIDEO BLITTER AUDIO FLOPPY A1200_IDE KEYBOARD MOUSE SERIAL PARALLEL A2000_CLK CHIP_RAM PAULA
Zone ranges:
DMA [mem 0x0000000040000000-0x000004dfffffffff]
Normal empty
Movable zone start for each node
Early memory node ranges
node 0: [mem 0x0000000040000000-0x000000004dffffff]
Initmem setup node 0 [mem 0x0000000040000000-0x000000004dffffff]
pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768
pcpu-alloc: [0] 0
Kernel command line: root=/dev/sda4 debug=ser earlyprintk console=ttyS0,9600n8
Dentry cache hash table entries: 32768 (order: 5, 131072 bytes, linear)
Inode-cache hash table entries: 16384 (order: 4, 65536 bytes, linear)
Sorting __ex_table...
Built 1 zonelists, mobility grouping on. Total pages: 56840
mem auto-init: stack:all(zero), heap alloc:off, heap free:off
Memory: 221284K/229376K available (3753K kernel code, 472K rwdata, 1184K rodata, 172K init, 149K bss, 8092K reserved, 0K c)
SLUB: HWalign=16, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
start_kernel::941
start_kernel::976
NR_IRQS: 32
clocksource: ciab: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 2694272661900 ns
start_kernel::990
start_kernel::994
start_kernel::998
start_kernel::1000
start_kernel::1006
start_kernel::1009

I've added some printk around init/main.c::start_kernel() and it *appears* to be
hanging in "local_irq_enable();".

I've tried all stable LTS kernels from 4.4.y to 6.6.y, and they all shows the same
exact symptoms.

Hope it rings a bell.

1: https://amigawarp.eu/product/warp-1260-board-for-amiga-1200/
--
bye,
p.