Re: [hatari-devel] SCU/VME register access?

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

On 5.6.2024 12.46, Nicolas Pomarède wrote:
> 4 years later, time to resurrect this old thread :)
>
> Are there any ready to use linux disk image I could use to check the 
> boot process regarding SCU registers ?

If you're using Debian, it's easy to build latest m68k Linux kernel.

Just copy-paste the commands given in the "3. Building m68k kernel" 
section of the Hatari "m68k-linux.txt" doc (with "/path/to/hatari" parts 
replaced by path to your Hatari checkout).

If you do not have Debian, I can mail you the kernel and its symbols 
file (about 5MB uncompressed).


Example in "6. Running Hatari" section tells how to run that Linux 
kernel with Hatari.

As TT SCU is accessed already at Linux boot, you do not need a disk 
image i.e. you can drop the "--ide-master" option (besides replacing 
"falcon" with "tt"). [1]


> I know there's also the SysV disk images at http://www.atariunix.com/ 
> but it seems they also rely on the RTC's internal timer interrupt, which 
> is not emulated so far
>
> Or some other programs that modify SCU registers ? (apart from the TOS 
> used in MegaSTE / TT)

This is shown by "--trace vme" on latest m68k Linux v6.9:
---------------------------------------------------
....
VME: SCU read  (0xff8e01): 0x00
....
NR_IRQS: 141
VME: SCU write (0xff8e01): 0x10 (system interrupt mask)
VME: SCU write (0xff8e0d): 0x60 (VME interrupt mask)
clocksource: mfp: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 
77769386670404 ns
unexpected interrupt from 112
Console: colour dummy device 80x25
printk: legacy console [tty0] enabled
unexpected interrupt from 112
....
unexpected interrupt from 104
....
---------------------------------------------------

(After which there are constant messages of both 104 & 112 interrupts.)


Whereas with "--vme off", linux boots to user-space just fine under TT 
emulation.


	- Eero

[1] Section "4. Building root file system" gives commands for building 
two different root file systems from packages available on Debian, one 
based one Busybox, and another based on klibc utilities.