README
1Linux for the Q40
2=================
3
4You may try http://www.geocities.com/SiliconValley/Bay/2602/ for
5some up to date information. Booter and other tools will be also
6available from this place or http://ftp.uni-erlangen.de/pub/unix/Linux/680x0/q40/
7and mirrors.
8
9Hints to documentation usually refer to the linux source tree in
10/usr/src/linux/Documentation unless URL given.
11
12It seems IRQ unmasking can't be safely done on a Q40. IRQ probing
13is not implemented - do not try it! (See below)
14
15For a list of kernel command-line options read the documentation for the
16particular device drivers.
17
18The floppy imposes a very high interrupt load on the CPU, approx 30K/s.
19When something blocks interrupts (HD) it will lose some of them, so far
20this is not known to have caused any data loss. On highly loaded systems
21it can make the floppy very slow or practically stop. Other Q40 OS' simply
22poll the floppy for this reason - something that can't be done in Linux.
23Only possible cure is getting a 82072 controller with fifo instead of
24the 8272A.
25
26drivers used by the Q40, apart from the very obvious (console etc.):
27 drivers/char/q40_keyb.c # use PC keymaps for national keyboards
28 serial.c # normal PC driver - any speed
29 lp.c # printer driver
30 genrtc.c # RTC
31 char/joystick/* # most of this should work, not
32 # in default config.in
33 block/floppy.c # normal PC driver, DMA emu in asm/floppy.h
34 # and arch/m68k/kernel/entry.S
35 # see drivers/block/README.fd
36 ata/pata_falcon.c
37 net/ne.c
38 video/q40fb.c
39 parport/*
40 sound/dmasound_core.c
41 dmasound_q40.c
42
43Various other PC drivers can be enabled simply by adding them to
44arch/m68k/config.in, especially 8 bit devices should be without any
45problems. For cards using 16bit io/mem more care is required, like
46checking byte order issues, hacking memcpy_*_io etc.
47
48
49Debugging
50=========
51
52Upon startup the kernel will usually output "ABCQGHIJ" into the SRAM,
53preceded by the booter signature. This is a trace just in case something
54went wrong during earliest setup stages of head.S.
55**Changed** to preserve SRAM contents by default, this is only done when
56requested - SRAM must start with '%LX$' signature to do this. '-d' option
57to 'lxx' loader enables this.
58
59SRAM can also be used as additional console device, use debug=mem.
60This will save kernel startup msgs into SRAM, the screen will display
61only the penguin - and shell prompt if it gets that far..
62Unfortunately only 2000 bytes are available.
63
64Serial console works and can also be used for debugging, see loader_txt
65
66Most problems seem to be caused by fawlty or badly configured io-cards or
67hard drives anyway.
68Make sure to configure the parallel port as SPP and remove IRQ/DMA jumpers
69for first testing. The Q40 does not support DMA and may have trouble with
70parallel ports version of interrupts.
71
72
73Q40 Hardware Description
74========================
75
76This is just an overview, see asm-m68k/* for details ask if you have any
77questions.
78
79The Q40 consists of a 68040@40 MHz, 1MB video RAM, up to 32MB RAM, AT-style
80keyboard interface, 1 Programmable LED, 2x8bit DACs and up to 1MB ROM, 1MB
81shadow ROM.
82The Q60 has any of 68060 or 68LC060 and up to 128 MB RAM.
83
84Most interfacing like floppy, IDE, serial and parallel ports is done via ISA
85slots. The ISA io and mem range is mapped (sparse&byteswapped!) into separate
86regions of the memory.
87The main interrupt register IIRQ_REG will indicate whether an IRQ was internal
88or from some ISA devices, EIRQ_REG can distinguish up to 8 ISA IRQs.
89
90The Q40 custom chip is programmable to provide 2 periodic timers:
91 - 50 or 200 Hz - level 2, !!THIS CAN'T BE DISABLED!!
92 - 10 or 20 KHz - level 4, used for dma-sound
93
94Linux uses the 200 Hz interrupt for timer and beep by default.
95
96
97Interrupts
98==========
99
100q40 master chip handles only a subset of level triggered interrupts.
101
102Linux has some requirements wrt interrupt architecture, these are
103to my knowledge:
104 (a) interrupt handler must not be reentered even when sti() is called
105 from within handler
106 (b) working enable/disable_irq
107
108Luckily these requirements are only important for drivers shared
109with other architectures - ide,serial,parallel, ethernet.
110q40ints.c now contains a trivial hack for (a), (b) is more difficult
111because only irq's 4-15 can be disabled - and only all of them at once.
112Thus disable_irq() can effectively block the machine if the driver goes
113asleep.
114One thing to keep in mind when hacking around the interrupt code is
115that there is no way to find out which IRQ caused a request, [EI]IRQ_REG
116displays current state of the various IRQ lines.
117
118Keyboard
119========
120
121q40 receives AT make/break codes from the keyboard, these are translated to
122the PC scancodes x86 Linux uses. So by theory every national keyboard should
123work just by loading the appropriate x86 keytable - see any national-HOWTO.
124
125Unfortunately the AT->PC translation isn't quite trivial and even worse, my
126documentation of it is absolutely minimal - thus some exotic keys may not
127behave exactly as expected.
128
129There is still hope that it can be fixed completely though. If you encounter
130problems, email me ideally this:
131 - exact keypress/release sequence
132 - 'showkey -s' run on q40, non-X session
133 - 'showkey -s' run on a PC, non-X session
134 - AT codes as displayed by the q40 debugging ROM
135btw if the showkey output from PC and Q40 doesn't differ then you have some
136classic configuration problem - don't send me anything in this case
137
138