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 6 available from this place or http://ftp.uni-erlangen.de/pub/unix/Linux/680x0/q40/ 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 34 ide* # see Documentation/ide.txt 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: 92 - 50 or 200 Hz - level 2, !!THIS CAN'T BE DISABLED!! 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 138 139