sparc64: Document PGD and PMD layout.

We're going to be messing around with the PMD interpretation and layout
for the sake of transparent huge pages, so we better clearly document what
we're starting with.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/sparc/include/asm/pgtable_64.h

@@ -63,6 +63,14 @@
 #error Page table parameters do not cover virtual address space properly.
 #endif
 
+/* PMDs point to PTE tables which are 4K aligned.  */
+#define PMD_PADDR	_AC(0xfffffffe,UL)
+#define PMD_PADDR_SHIFT	_AC(11,UL)
+
+/* PGDs point to PMD tables which are 8K aligned.  */
+#define PGD_PADDR	_AC(0xfffffffc,UL)
+#define PGD_PADDR_SHIFT	_AC(11,UL)
+
 #ifndef __ASSEMBLY__
 
 #include <linux/sched.h>
@@ -581,14 +589,14 @@ static inline unsigned long pte_special(pte_t pte)
 }
 
 #define pmd_set(pmdp, ptep)	\
-	(pmd_val(*(pmdp)) = (__pa((unsigned long) (ptep)) >> 11UL))
+	(pmd_val(*(pmdp)) = (__pa((unsigned long) (ptep)) >> PMD_PADDR_SHIFT))
 #define pud_set(pudp, pmdp)	\
-	(pud_val(*(pudp)) = (__pa((unsigned long) (pmdp)) >> 11UL))
+	(pud_val(*(pudp)) = (__pa((unsigned long) (pmdp)) >> PGD_PADDR_SHIFT))
 #define __pmd_page(pmd)		\
-	((unsigned long) __va((((unsigned long)pmd_val(pmd))<<11UL)))
+	((unsigned long) __va((((unsigned long)pmd_val(pmd))<<PMD_PADDR_SHIFT)))
 #define pmd_page(pmd) 			virt_to_page((void *)__pmd_page(pmd))
 #define pud_page_vaddr(pud)		\
-	((unsigned long) __va((((unsigned long)pud_val(pud))<<11UL)))
+	((unsigned long) __va((((unsigned long)pud_val(pud))<<PGD_PADDR_SHIFT)))
 #define pud_page(pud) 			virt_to_page((void *)pud_page_vaddr(pud))
 #define pmd_none(pmd)			(!pmd_val(pmd))
 #define pmd_bad(pmd)			(0)

arch/sparc/include/asm/tsb.h

@@ -147,13 +147,13 @@ extern struct tsb_phys_patch_entry __tsb_phys_patch, __tsb_phys_patch_end;
 	brz,pn		REG1, FAIL_LABEL; \
 	 sllx		VADDR, 64 - (PMD_SHIFT + PMD_BITS), REG2; \
 	srlx		REG2, 64 - PAGE_SHIFT, REG2; \
-	sllx		REG1, 11, REG1; \
+	sllx		REG1, PGD_PADDR_SHIFT, REG1; \
 	andn		REG2, 0x3, REG2; \
 	lduwa		[REG1 + REG2] ASI_PHYS_USE_EC, REG1; \
 	brz,pn		REG1, FAIL_LABEL; \
 	 sllx		VADDR, 64 - PMD_SHIFT, REG2; \
 	srlx		REG2, 64 - (PAGE_SHIFT - 1), REG2; \
-	sllx		REG1, 11, REG1; \
+	sllx		REG1, PMD_PADDR_SHIFT, REG1; \
 	andn		REG2, 0x7, REG2; \
 	add		REG1, REG2, REG1;
 
@@ -172,13 +172,13 @@ extern struct tsb_phys_patch_entry __tsb_phys_patch, __tsb_phys_patch_end;
 	brz,pn		REG1, FAIL_LABEL; \
 	 sllx		VADDR, 64 - (PMD_SHIFT + PMD_BITS), REG2; \
 	srlx		REG2, 64 - PAGE_SHIFT, REG2; \
-	sllx		REG1, 11, REG1; \
+	sllx		REG1, PGD_PADDR_SHIFT, REG1; \
 	andn		REG2, 0x3, REG2; \
 	lduwa		[REG1 + REG2] ASI_PHYS_USE_EC, REG1; \
 	brz,pn		REG1, FAIL_LABEL; \
 	 sllx		VADDR, 64 - PMD_SHIFT, REG2; \
 	srlx		REG2, 64 - (PAGE_SHIFT - 1), REG2; \
-	sllx		REG1, 11, REG1; \
+	sllx		REG1, PMD_PADDR_SHIFT, REG1; \
 	andn		REG2, 0x7, REG2; \
 	add		REG1, REG2, REG1;