ACPI tables follow a tree structure in memory.
The root of the tree is the RSDP (Root System Description Pointer).
To find the RSDP, the OS searches for the signature "RSD PTR "
in well known physical memory locations. Then the OS computes
a table checksum to verify that the signature is really part
of a valid table header.
Some systems have a proper signature but an invalid checksum;
followed elsewhere by a proper signature with valid checksum.
http://bugzilla.kernel.org/show_bug.cgi?id=9444
The Linux RSDP scanning code bailed out on those systems
and as a result they booted with ACPI disabled.
Fix this by deleting the Linux RSDP scanning code and
plugging in the ACPICA RSDP scanning code.
Signed-off-by: Len Brown <len.brown@intel.com>
239665a3bb