[PARISC] parisc specific kmap API implementation for pa8800

This patch fixes the pa8800 at a gross level (there are still other
subtle incoherency issues which can still cause crashes and HPMCs).

What it does is try to force eject inequivalent aliases before they
become visible to the L2 cache (which is where we get the incoherence
problems).

A new function (parisc_requires_coherency) is introduced in
asm/processor.h to identify the pa8x00 processors (8800 and 8900)
which have the issue.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/include/asm-parisc/processor.h b/include/asm-parisc/processor.h
index c72b8fa4968..4313618c98e 100644
--- a/include/asm-parisc/processor.h
+++ b/include/asm-parisc/processor.h
@@ -332,6 +332,19 @@ extern unsigned long get_wchan(struct task_struct *p);
 
 #define cpu_relax()     barrier()
 
+/* Used as a macro to identify the combined VIPT/PIPT cached
+ * CPUs which require a guarantee of coherency (no inequivalent
+ * aliases with different data, whether clean or not) to operate */
+static inline int parisc_requires_coherency(void)
+{
+#ifdef CONFIG_PA8X00
+        /* FIXME: also pa8900 - when we see one */
+        return boot_cpu_data.cpu_type == mako;
+#else
+        return 0;
+#endif
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* __ASM_PARISC_PROCESSOR_H */