powerpc/mm: Split the various pgtable-* headers based on MMU type

This patch moves the definition of the PTE format for each MMU type
to separate files instead of all in one file. This improves overall
maintainability and will make it easier to add new types.

On 64-bit, additionally, I've separated the headers relative to the
format of the page table tree (3 vs. 4 levels for 64K vs 4K pages)
from the headers specific to the PTE format for hash based processors,
this will make it easier to add support for Book3 "E" 64-bit
implementations.

There are still some type-related ifdef's in the generic headers,
we might remove them in the long run, but this patch shouldn't result
in any code change, -hopefully- just definitions being moved around.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 64 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/pte-8xx.h b/arch/powerpc/include/asm/pte-8xx.h
new file mode 100644
index 0000000..b07acfd
--- /dev/null
+++ b/arch/powerpc/include/asm/pte-8xx.h
@@ -0,0 +1,64 @@
+#ifndef _ASM_POWERPC_PTE_8xx_H
+#define _ASM_POWERPC_PTE_8xx_H
+#ifdef __KERNEL__
+
+/*
+ * The PowerPC MPC8xx uses a TLB with hardware assisted, software tablewalk.
+ * We also use the two level tables, but we can put the real bits in them
+ * needed for the TLB and tablewalk.  These definitions require Mx_CTR.PPM = 0,
+ * Mx_CTR.PPCS = 0, and MD_CTR.TWAM = 1.  The level 2 descriptor has
+ * additional page protection (when Mx_CTR.PPCS = 1) that allows TLB hit
+ * based upon user/super access.  The TLB does not have accessed nor write
+ * protect.  We assume that if the TLB get loaded with an entry it is
+ * accessed, and overload the changed bit for write protect.  We use
+ * two bits in the software pte that are supposed to be set to zero in
+ * the TLB entry (24 and 25) for these indicators.  Although the level 1
+ * descriptor contains the guarded and writethrough/copyback bits, we can
+ * set these at the page level since they get copied from the Mx_TWC
+ * register when the TLB entry is loaded.  We will use bit 27 for guard, since
+ * that is where it exists in the MD_TWC, and bit 26 for writethrough.
+ * These will get masked from the level 2 descriptor at TLB load time, and
+ * copied to the MD_TWC before it gets loaded.
+ * Large page sizes added.  We currently support two sizes, 4K and 8M.
+ * This also allows a TLB hander optimization because we can directly
+ * load the PMD into MD_TWC.  The 8M pages are only used for kernel
+ * mapping of well known areas.  The PMD (PGD) entries contain control
+ * flags in addition to the address, so care must be taken that the
+ * software no longer assumes these are only pointers.
+ */
+
+/* Definitions for 8xx embedded chips. */
+#define _PAGE_PRESENT	0x0001	/* Page is valid */
+#define _PAGE_FILE	0x0002	/* when !present: nonlinear file mapping */
+#define _PAGE_NO_CACHE	0x0002	/* I: cache inhibit */
+#define _PAGE_SHARED	0x0004	/* No ASID (context) compare */
+
+/* These five software bits must be masked out when the entry is loaded
+ * into the TLB.
+ */
+#define _PAGE_EXEC	0x0008	/* software: i-cache coherency required */
+#define _PAGE_GUARDED	0x0010	/* software: guarded access */
+#define _PAGE_DIRTY	0x0020	/* software: page changed */
+#define _PAGE_RW	0x0040	/* software: user write access allowed */
+#define _PAGE_ACCESSED	0x0080	/* software: page referenced */
+
+/* Setting any bits in the nibble with the follow two controls will
+ * require a TLB exception handler change.  It is assumed unused bits
+ * are always zero.
+ */
+#define _PAGE_HWWRITE	0x0100	/* h/w write enable: never set in Linux PTE */
+#define _PAGE_USER	0x0800	/* One of the PP bits, the other is USER&~RW */
+
+#define _PMD_PRESENT	0x0001
+#define _PMD_BAD	0x0ff0
+#define _PMD_PAGE_MASK	0x000c
+#define _PMD_PAGE_8M	0x000c
+
+#define _PTE_NONE_MASK _PAGE_ACCESSED
+
+/* Until my rework is finished, 8xx still needs atomic PTE updates */
+#define PTE_ATOMIC_UPDATES	1
+
+
+#endif /* __KERNEL__ */
+#endif /*  _ASM_POWERPC_PTE_8xx_H */