bootstrap stuffs

Benjamin Herrenschmidt bh40 at
Wed Feb 17 05:11:48 EST 1999

On Tue, Feb 16, 1999, Gabriel Paubert <paubert at> wrote:

>So, if I'm not mistaken, a read from the same location is the only
>operation that guarantees that the register has actually been updated, but
>it's even slower than a sync :-(

On a side note, there is an interesting implementation of interrupts in
MkLinux mach kernel. Since they consider the controller as a really slow
device (and this seems to be confirmed by the bogus interrupt we had on
PowerMacs), they actually do it differently:

Mach maintains the current interrupt mask locally in RAM. When it
disables an interrupt, it does so only in the mask, the controller gets
updated only if this interrupt actually occurs. The enable code will
enable it in the mask only if it has been disabled by the interrupt.

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