arch/m68k/q40/README

Source file repositories/reference/linux-study-clean/arch/m68k/q40/README

File Facts

System
Linux kernel
Corpus path
arch/m68k/q40/README
Extension
[no extension]
Size
5470 bytes
Lines
138
Domain
Architecture Layer
Bucket
arch/m68k
Inferred role
Architecture Layer: arch/m68k
Status
atlas-only

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

Linux for the Q40
=================

You may try http://www.geocities.com/SiliconValley/Bay/2602/ for
some up to date information. Booter and other tools will be also
available from this place or http://ftp.uni-erlangen.de/pub/unix/Linux/680x0/q40/
and mirrors.

Hints to documentation usually refer to the linux source tree in
/usr/src/linux/Documentation unless URL given.

It seems IRQ unmasking can't be safely done on a Q40. IRQ probing
is not implemented - do not try it! (See below)

For a list of kernel command-line options read the documentation for the
particular device drivers.

The floppy imposes a very high interrupt load on the CPU, approx 30K/s.
When something blocks interrupts (HD) it will lose some of them, so far
this is not known to have caused any data loss. On highly loaded systems
it can make the floppy very slow or practically stop. Other Q40 OS' simply
poll the floppy for this reason - something that can't be done in Linux.
Only possible cure is getting a 82072 controller with fifo instead of
the 8272A.

drivers used by the Q40, apart from the very obvious (console etc.):
	drivers/char/q40_keyb.c		# use PC keymaps for national keyboards
		     serial.c		# normal PC driver - any speed
	             lp.c		# printer driver
		     genrtc.c		# RTC
		char/joystick/*		# most of this should work, not
				        # in default config.in
	        block/floppy.c		# normal PC driver, DMA emu in asm/floppy.h
					# and arch/m68k/kernel/entry.S
					# see drivers/block/README.fd
		ata/pata_falcon.c
		net/ne.c
		video/q40fb.c
		parport/*
		sound/dmasound_core.c
		      dmasound_q40.c

Various other PC drivers can be enabled simply by adding them to
arch/m68k/config.in, especially 8 bit devices should be without any
problems. For cards using 16bit io/mem more care is required, like
checking byte order issues, hacking memcpy_*_io etc.


Debugging
=========

Upon startup the kernel will usually output "ABCQGHIJ" into the SRAM,
preceded by the booter signature. This is a trace just in case something
went wrong during earliest setup stages of head.S.
**Changed** to preserve SRAM contents by default, this is only done when
requested - SRAM must start with '%LX$' signature to do this. '-d' option
to 'lxx' loader enables this.

SRAM can also be used as additional console device, use debug=mem.
This will save kernel startup msgs into SRAM, the screen will display
only the penguin - and shell prompt if it gets that far..
Unfortunately only 2000 bytes are available.

Serial console works and can also be used for debugging, see loader_txt

Most problems seem to be caused by fawlty or badly configured io-cards or
hard drives anyway.
Make sure to configure the parallel port as SPP and remove IRQ/DMA jumpers
for first testing. The Q40 does not support DMA and may have trouble with
parallel ports version of interrupts.

Annotation

Implementation Notes