David Rusling writes:
> [1] Turning off the I and D caches (and write buffer) in proc-sa110.S is
> a _good_ thing.
In 2.3, if you believe that some post-boot D cache or write buffer behaviour is
causing problems, you can disable these by supplying a kernel parameter.
> [3] I always enable enough IO space (in head-armv.S) to light leds. This
> way I can tell where I am in the boot sequence. Once you get past setup.c
> (mostly a case of recognising the CPU correctly), the MMU setup is
> the hardest bit. I use mm-armv.c and include a table. Getting through
> MMU setup is straight forward (although I have been terminally confused
> here myself).
This is now the only way to do it in 2.3. You just supply the relevent
table describing the mapping you desire, and the generic code takes care
of actually setting it up.
> [3a] There's a gotcha in the memory initialisation. You need to set up
> the initial page tables so that 0xC000.0000 is the physical address of
> the base of memory and NOT 0x0000.0000 (sorry, this is SA-1100
> only). Look at mm/mm-rpc.c in init_dram_banks() - it's the line
> current->tss.memmap = __virt_to_phys(). Otherwise, once you have
> booted, when the idle task cuts in, it will crash.
This no longer applies in 2.3 - it's all handled automagically.
> [5] I've used a very simple serial driver so that console messages come
> out easily (polled). Consoles are wierd - Linux uses the first console
> registered during the boot but quite which device that is when /sbin/init
> runs depends on your file system (what does /dev/console point to?).
> I use /dev/console as character device 5,1.
/dev/console should always be character device 5,1, as specified by the
Filesystem Hierarchy Standard, and the authoritive device registration
document included with the Linux kernel. Anything else is just broken
and will not work as expected.
In that case, the device which turns out to be the console can be controlled
by using the "console=" kernel parameter.
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