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1 | Linux for the Q40 |
2 | ================= | |
3 | ||
4 | You may try http://www.geocities.com/SiliconValley/Bay/2602/ for | |
5 | some up to date information. Booter and other tools will be also | |
50a23e6e | 6 | available from this place or http://ftp.uni-erlangen.de/pub/unix/Linux/680x0/q40/ |
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7 | and mirrors. |
8 | ||
9 | Hints to documentation usually refer to the linux source tree in | |
10 | /usr/src/linux/Documentation unless URL given. | |
11 | ||
12 | It seems IRQ unmasking can't be safely done on a Q40. IRQ probing | |
13 | is not implemented - do not try it! (See below) | |
14 | ||
15 | For a list of kernel command-line options read the documentation for the | |
16 | particular device drivers. | |
17 | ||
18 | The floppy imposes a very high interrupt load on the CPU, approx 30K/s. | |
19 | When something blocks interrupts (HD) it will lose some of them, so far | |
20 | this is not known to have caused any data loss. On highly loaded systems | |
21 | it can make the floppy very slow or practically stop. Other Q40 OS' simply | |
22 | poll the floppy for this reason - something that can't be done in Linux. | |
23 | Only possible cure is getting a 82072 controller with fifo instead of | |
24 | the 8272A. | |
25 | ||
26 | drivers 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/q40ide.c # startup for ide | |
395cf969 | 34 | ide* # see Documentation/ide/ide.txt |
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35 | floppy.c # normal PC driver, DMA emu in asm/floppy.h |
36 | # and arch/m68k/kernel/entry.S | |
37 | # see drivers/block/README.fd | |
38 | net/ne.c | |
39 | video/q40fb.c | |
40 | parport/* | |
41 | sound/dmasound_core.c | |
42 | dmasound_q40.c | |
43 | ||
44 | Various other PC drivers can be enabled simply by adding them to | |
45 | arch/m68k/config.in, especially 8 bit devices should be without any | |
46 | problems. For cards using 16bit io/mem more care is required, like | |
47 | checking byte order issues, hacking memcpy_*_io etc. | |
48 | ||
49 | ||
50 | Debugging | |
51 | ========= | |
52 | ||
53 | Upon startup the kernel will usually output "ABCQGHIJ" into the SRAM, | |
54 | preceded by the booter signature. This is a trace just in case something | |
55 | went wrong during earliest setup stages of head.S. | |
56 | **Changed** to preserve SRAM contents by default, this is only done when | |
57 | requested - SRAM must start with '%LX$' signature to do this. '-d' option | |
58 | to 'lxx' loader enables this. | |
59 | ||
60 | SRAM can also be used as additional console device, use debug=mem. | |
61 | This will save kernel startup msgs into SRAM, the screen will display | |
62 | only the penguin - and shell prompt if it gets that far.. | |
63 | Unfortunately only 2000 bytes are available. | |
64 | ||
65 | Serial console works and can also be used for debugging, see loader_txt | |
66 | ||
67 | Most problems seem to be caused by fawlty or badly configured io-cards or | |
68 | hard drives anyway. | |
69 | Make sure to configure the parallel port as SPP and remove IRQ/DMA jumpers | |
70 | for first testing. The Q40 does not support DMA and may have trouble with | |
71 | parallel ports version of interrupts. | |
72 | ||
73 | ||
74 | Q40 Hardware Description | |
75 | ======================== | |
76 | ||
77 | This is just an overview, see asm-m68k/* for details ask if you have any | |
78 | questions. | |
79 | ||
80 | The Q40 consists of a 68040@40 MHz, 1MB video RAM, up to 32MB RAM, AT-style | |
81 | keyboard interface, 1 Programmable LED, 2x8bit DACs and up to 1MB ROM, 1MB | |
82 | shadow ROM. | |
83 | The Q60 has any of 68060 or 68LC060 and up to 128 MB RAM. | |
84 | ||
85 | Most interfacing like floppy, IDE, serial and parallel ports is done via ISA | |
86 | slots. The ISA io and mem range is mapped (sparse&byteswapped!) into separate | |
87 | regions of the memory. | |
88 | The main interrupt register IIRQ_REG will indicate whether an IRQ was internal | |
89 | or from some ISA devices, EIRQ_REG can distinguish up to 8 ISA IRQs. | |
90 | ||
91 | The Q40 custom chip is programmable to provide 2 periodic timers: | |
25985edc | 92 | - 50 or 200 Hz - level 2, !!THIS CAN'T BE DISABLED!! |
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93 | - 10 or 20 KHz - level 4, used for dma-sound |
94 | ||
95 | Linux uses the 200 Hz interrupt for timer and beep by default. | |
96 | ||
97 | ||
98 | Interrupts | |
99 | ========== | |
100 | ||
101 | q40 master chip handles only a subset of level triggered interrupts. | |
102 | ||
103 | Linux has some requirements wrt interrupt architecture, these are | |
104 | to my knowledge: | |
105 | (a) interrupt handler must not be reentered even when sti() is called | |
106 | from within handler | |
107 | (b) working enable/disable_irq | |
108 | ||
109 | Luckily these requirements are only important for drivers shared | |
110 | with other architectures - ide,serial,parallel, ethernet. | |
111 | q40ints.c now contains a trivial hack for (a), (b) is more difficult | |
112 | because only irq's 4-15 can be disabled - and only all of them at once. | |
113 | Thus disable_irq() can effectively block the machine if the driver goes | |
114 | asleep. | |
115 | One thing to keep in mind when hacking around the interrupt code is | |
116 | that there is no way to find out which IRQ caused a request, [EI]IRQ_REG | |
117 | displays current state of the various IRQ lines. | |
118 | ||
119 | Keyboard | |
120 | ======== | |
121 | ||
122 | q40 receives AT make/break codes from the keyboard, these are translated to | |
123 | the PC scancodes x86 Linux uses. So by theory every national keyboard should | |
124 | work just by loading the appropriate x86 keytable - see any national-HOWTO. | |
125 | ||
126 | Unfortunately the AT->PC translation isn't quite trivial and even worse, my | |
127 | documentation of it is absolutely minimal - thus some exotic keys may not | |
128 | behave exactly as expected. | |
129 | ||
130 | There is still hope that it can be fixed completely though. If you encounter | |
131 | problems, email me ideally this: | |
132 | - exact keypress/release sequence | |
133 | - 'showkey -s' run on q40, non-X session | |
134 | - 'showkey -s' run on a PC, non-X session | |
135 | - AT codes as displayed by the q40 debugging ROM | |
136 | btw if the showkey output from PC and Q40 doesn't differ then you have some | |
137 | classic configuration problem - don't send me anything in this case | |
138 |