diff options
Diffstat (limited to 'Documentation/sh/register-banks.txt')
| -rw-r--r-- | Documentation/sh/register-banks.txt | 33 |
1 files changed, 0 insertions, 33 deletions
diff --git a/Documentation/sh/register-banks.txt b/Documentation/sh/register-banks.txt deleted file mode 100644 index a6719f2f6594..000000000000 --- a/Documentation/sh/register-banks.txt +++ /dev/null @@ -1,33 +0,0 @@ - Notes on register bank usage in the kernel - ========================================== - -Introduction ------------- - -The SH-3 and SH-4 CPU families traditionally include a single partial register -bank (selected by SR.RB, only r0 ... r7 are banked), whereas other families -may have more full-featured banking or simply no such capabilities at all. - -SR.RB banking -------------- - -In the case of this type of banking, banked registers are mapped directly to -r0 ... r7 if SR.RB is set to the bank we are interested in, otherwise ldc/stc -can still be used to reference the banked registers (as r0_bank ... r7_bank) -when in the context of another bank. The developer must keep the SR.RB value -in mind when writing code that utilizes these banked registers, for obvious -reasons. Userspace is also not able to poke at the bank1 values, so these can -be used rather effectively as scratch registers by the kernel. - -Presently the kernel uses several of these registers. - - - r0_bank, r1_bank (referenced as k0 and k1, used for scratch - registers when doing exception handling). - - r2_bank (used to track the EXPEVT/INTEVT code) - - Used by do_IRQ() and friends for doing irq mapping based off - of the interrupt exception vector jump table offset - - r6_bank (global interrupt mask) - - The SR.IMASK interrupt handler makes use of this to set the - interrupt priority level (used by local_irq_enable()) - - r7_bank (current) - |