tree 7b9707625fe89d567ceef4f6a8816807a3de5f3d
parent fff69fd03d1290297fcd039b07819fafa69ffc0a
author Christophe Leroy <christophe.leroy@c-s.fr> 1471960736 +0200
committer Scott Wood <oss@buserror.net> 1474789133 -0500

powerpc/8xx: use SPRN_EIE and SPRN_EID to enable/disable interrupts

The 8xx has two special registers called EID (External Interrupt
Disable) and EIE (External Interrupt Enable) for clearing/setting
EE in MSR. It avoids the three instructions set mfmsr/ori/mtmsr or
mfmsr/rlwinm/mtmsr and it avoids using a general register.

We just have to write something in the special register to change MSR EE
bit. So we write r0 into the register, regardless of r0 value.

Writing to one of those two special registers also set the MSR RI bit,
but this bit is only unset during beginning of exception prolog and end
of exception epilog. When executing C-functions MSR RI is always set.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Scott Wood <oss@buserror.net>