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diff --git a/arch/m68k/q40/README b/arch/m68k/q40/README new file mode 100644 index 000000000..93f4c4cd3 --- /dev/null +++ b/arch/m68k/q40/README @@ -0,0 +1,138 @@ +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/q40ide.c # startup for ide + ide* # see Documentation/ide/ide.txt + floppy.c # normal PC driver, DMA emu in asm/floppy.h + # and arch/m68k/kernel/entry.S + # see drivers/block/README.fd + 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. + + +Q40 Hardware Description +======================== + +This is just an overview, see asm-m68k/* for details ask if you have any +questions. + +The Q40 consists of a 68040@40 MHz, 1MB video RAM, up to 32MB RAM, AT-style +keyboard interface, 1 Programmable LED, 2x8bit DACs and up to 1MB ROM, 1MB +shadow ROM. +The Q60 has any of 68060 or 68LC060 and up to 128 MB RAM. + +Most interfacing like floppy, IDE, serial and parallel ports is done via ISA +slots. The ISA io and mem range is mapped (sparse&byteswapped!) into separate +regions of the memory. +The main interrupt register IIRQ_REG will indicate whether an IRQ was internal +or from some ISA devices, EIRQ_REG can distinguish up to 8 ISA IRQs. + +The Q40 custom chip is programmable to provide 2 periodic timers: + - 50 or 200 Hz - level 2, !!THIS CAN'T BE DISABLED!! + - 10 or 20 KHz - level 4, used for dma-sound + +Linux uses the 200 Hz interrupt for timer and beep by default. + + +Interrupts +========== + +q40 master chip handles only a subset of level triggered interrupts. + +Linux has some requirements wrt interrupt architecture, these are +to my knowledge: + (a) interrupt handler must not be reentered even when sti() is called + from within handler + (b) working enable/disable_irq + +Luckily these requirements are only important for drivers shared +with other architectures - ide,serial,parallel, ethernet. +q40ints.c now contains a trivial hack for (a), (b) is more difficult +because only irq's 4-15 can be disabled - and only all of them at once. +Thus disable_irq() can effectively block the machine if the driver goes +asleep. +One thing to keep in mind when hacking around the interrupt code is +that there is no way to find out which IRQ caused a request, [EI]IRQ_REG +displays current state of the various IRQ lines. + +Keyboard +======== + +q40 receives AT make/break codes from the keyboard, these are translated to +the PC scancodes x86 Linux uses. So by theory every national keyboard should +work just by loading the appropriate x86 keytable - see any national-HOWTO. + +Unfortunately the AT->PC translation isn't quite trivial and even worse, my +documentation of it is absolutely minimal - thus some exotic keys may not +behave exactly as expected. + +There is still hope that it can be fixed completely though. If you encounter +problems, email me ideally this: + - exact keypress/release sequence + - 'showkey -s' run on q40, non-X session + - 'showkey -s' run on a PC, non-X session + - AT codes as displayed by the q40 debugging ROM +btw if the showkey output from PC and Q40 doesn't differ then you have some +classic configuration problem - don't send me anything in this case + |