[PARISC] Make sure use of RFI conforms to PA 2.0 and 1.1 arch docs

2.6.12-rc4-pa3 : first pass at making sure use of RFI conforms to
PA 2.0 arch pages F-4 and F-5, PA 1.1 Arch page 3-19 and 3-20.

The discussion revolves around all the rules for clearing PSW Q-bit.
The hard part is meeting all the rules for "relied upon translation".

.align directive is used to guarantee the critical sequence ends more than
8 instructions (32 bytes) from the end of page.

Signed-off-by: Grant Grundler <grundler@parisc-linux.org>

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/include/asm-parisc/assembly.h b/include/asm-parisc/assembly.h
index 30b023411fef..b24a99e3ef9c 100644
--- a/include/asm-parisc/assembly.h
+++ b/include/asm-parisc/assembly.h
@@ -450,5 +450,30 @@
         REST_CR (%cr22, PT_PSW  (\regs))
         .endm
 
+
+        /* First step to create a "relied upon translation"
+         * See PA 2.0 Arch. page F-4 and F-5.
+         *
+         * The ssm was originally necessary due to a "PCxT bug".
+         * But someone decided it needed to be added to the architecture
+         * and this "feature" went into rev3 of PA-RISC 1.1 Arch Manual.
+         * It's been carried forward into PA 2.0 Arch as well. :^(
+         *
+         * "ssm 0,%r0" is a NOP with side effects (prefetch barrier).
+         * rsm/ssm prevents the ifetch unit from speculatively fetching
+         * instructions past this line in the code stream.
+         * PA 2.0 processor will single step all insn in the same QUAD (4 insn).
+         */
+        .macro  pcxt_ssm_bug
+        rsm     PSW_SM_I,%r0
+        nop     /* 1 */
+        nop     /* 2 */
+        nop     /* 3 */
+        nop     /* 4 */
+        nop     /* 5 */
+        nop     /* 6 */
+        nop     /* 7 */
+        .endm
+
 #endif /* __ASSEMBLY__ */
 #endif