Name
mtrr_add -- Add a memory type region
Synopsis
int mtrr_add (unsigned long base, unsigned long size, unsigned int type, char increment);
Arguments
- base
Physical base address of region
- size
Physical size of region
- type
Type of MTRR desired
- increment
If this is true do usage counting on the region
Description
Memory type region registers control the caching on newer Intel and
non Intel processors. This function allows drivers to request an
MTRR is added. The details and hardware specifics of each processor's
implementation are hidden from the caller, but nevertheless the
caller should expect to need to provide a power of two size on an
equivalent power of two boundary.
If the region cannot be added either because all regions are in use
or the CPU cannot support it a negative value is returned. On success
the register number for this entry is returned, but should be treated
as a cookie only.
On a multiprocessor machine the changes are made to all processors.
This is required on x86 by the Intel processors.
The available types are
MTRR_TYPE_UNCACHEABLE - No caching
MTRR_TYPE_WRITEBACK - Write data back in bursts whenever
MTRR_TYPE_WRCOMB - Write data back soon but allow bursts
MTRR_TYPE_WRTHROUGH - Cache reads but not writes
BUGS
Needs a quiet flag for the cases where drivers do not mind
failures and do not wish system log messages to be sent.