I/O processors:
* The i80200 and the i80321 have the same CPU ID, so split the
CPU_XSCALE option into CPU_XSCALE_80200 and CPU_XSCALE_80321
options, and don't let them both be defined at the same time.
XXX May want to revisit this in the future.
* Split some registers common between the i80200 and i80321 into
<arm/xscale/xscalereg.h>.
* Rename a few existing functions.
pmap_copy_page() will never have any mappings. Therefore, it
is unnecessary to do a cache clean for that page.
Add assertions in #ifdef DEBUG that assert this invariant.
This shaves some cycles off the frequently-called pmap_zero_page()
and pmap_copy_page() (no need to look up the dst page's vm_page
structure, and one less function call to clean the page).
incorporate write back support for processors not having a write through
cache.
The current fb_devconfig structure now really holds the device's
configuration and the softc really only holds the attachment information.
This used to be mixed giving rise to weird stuctures and cross references.
The number of vertical syncs before the video memory writeback is triggered
is configurable ... default is to wait for 5 Vsync .. aprox minumum 10
times a second, but more likely in the order of 12,5 times a second. When
printing is in progress no write back is performed... only after the
waiting time. The reasoning behind this is that as long as the screen is
printed too the cache will be purged of dirty data anyway due to the
processing and new screen memory useage.
on the port-acorn32's TODO list for quite some time :
- when the serial console is selected, don't exclude the screen
alltogether; currently the keyboard is still not attached but that might be
a configuration problem in the GENERIC console or a failure to explicitly
connect to a wsmux. This needs further investigation.
- create a framework for the display memory writeback on vsync for
StrongARM processors since they don't have a write-trough cache. This is to
solve the lazy screen update that is very evident in single user mode on
these processors; the cache isn't flushed/written back that often and parts
of the screen can thus be resident in the cache but not written out to
memory yet.
- clean up some loose ends in the code.
