1Linux for the Q40
   4You may try for
   5some up to date information. Booter and other tools will be also
   6available from this place or
   7and mirrors.
   9Hints to documentation usually refer to the linux source tree in
  10/usr/src/linux/Documentation unless URL given.
  12It seems IRQ unmasking can't be safely done on a Q40. IRQ probing
  13is not implemented - do not try it! (See below)
  15For a list of kernel command-line options read the documentation for the
  16particular device drivers.
  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.
  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
  33                block/q40ide.c          # startup for ide
  34                      ide*              # see Documentation/ide/ide.rst
  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
  44Various other PC drivers can be enabled simply by adding them to
  45arch/m68k/, especially 8 bit devices should be without any
  46problems. For cards using 16bit io/mem more care is required, like
  47checking byte order issues, hacking memcpy_*_io etc.
  53Upon startup the kernel will usually output "ABCQGHIJ" into the SRAM,
  54preceded by the booter signature. This is a trace just in case something
  55went wrong during earliest setup stages of head.S.
  56**Changed** to preserve SRAM contents by default, this is only done when
  57requested - SRAM must start with '%LX$' signature to do this. '-d' option
  58to 'lxx' loader enables this.
  60SRAM can also be used as additional console device, use debug=mem.
  61This will save kernel startup msgs into SRAM, the screen will display
  62only the penguin - and shell prompt if it gets that far..
  63Unfortunately only 2000 bytes are available.
  65Serial console works and can also be used for debugging, see loader_txt
  67Most problems seem to be caused by fawlty or badly configured io-cards or
  68hard drives anyway.
  69Make sure to configure the parallel port as SPP and remove IRQ/DMA jumpers
  70for first testing. The Q40 does not support DMA and may have trouble with
  71parallel ports version of interrupts.
  74Q40 Hardware Description
  77This is just an overview, see asm-m68k/* for details ask if you have any
  80The Q40 consists of a 68040@40 MHz, 1MB video RAM, up to 32MB RAM, AT-style
  81keyboard interface, 1 Programmable LED, 2x8bit DACs and up to 1MB ROM, 1MB
  82shadow ROM.
  83The Q60 has any of 68060 or 68LC060 and up to 128 MB RAM.
  85Most interfacing like floppy, IDE, serial and parallel ports is done via ISA
  86slots. The ISA io and mem range is mapped (sparse&byteswapped!) into separate
  87regions of the memory.
  88The main interrupt register IIRQ_REG will indicate whether an IRQ was internal
  89or from some ISA devices, EIRQ_REG can distinguish up to 8 ISA IRQs.
  91The 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
  95Linux uses the 200 Hz interrupt for timer and beep by default.
 101q40 master chip handles only a subset of level triggered interrupts.
 103Linux has some requirements wrt interrupt architecture, these are
 104to 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
 109Luckily these requirements are only important for drivers shared
 110with other architectures - ide,serial,parallel, ethernet.
 111q40ints.c now contains a trivial hack for (a), (b) is more difficult
 112because only irq's 4-15 can be disabled - and only all of them at once.
 113Thus disable_irq() can effectively block the machine if the driver goes
 115One thing to keep in mind when hacking around the interrupt code is
 116that there is no way to find out which IRQ caused a request, [EI]IRQ_REG
 117displays current state of the various IRQ lines.
 122q40 receives AT make/break codes from the keyboard, these are translated to
 123the PC scancodes x86 Linux uses. So by theory every national keyboard should
 124work just by loading the appropriate x86 keytable - see any national-HOWTO.
 126Unfortunately the AT->PC translation isn't quite trivial and even worse, my
 127documentation of it is absolutely minimal - thus some exotic keys may not
 128behave exactly as expected.
 130There is still hope that it can be fixed completely though. If you encounter
 131problems, 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
 136btw if the showkey output from PC and Q40 doesn't differ then you have some
 137classic configuration problem - don't send me anything in this case