[src/trunk]: src/sys/arch/m68k/include - update some comments

[tsutsui <tsutsui%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/07df756203e1
branches:  trunk
changeset: 749953:07df756203e1
user:      tsutsui <tsutsui%NetBSD.org@localhost>
date:      Sun Dec 13 12:32:46 2009 +0000

description:
- update some comments
- use unsigned constant for shift op

diffstat:

 sys/arch/m68k/include/pmap_motorola.h |  20 +++++++++++---------
 1 files changed, 11 insertions(+), 9 deletions(-)

diffs (47 lines):

diff -r a7e75d98cd81 -r 07df756203e1 sys/arch/m68k/include/pmap_motorola.h
--- a/sys/arch/m68k/include/pmap_motorola.h     Sun Dec 13 12:21:26 2009 +0000
+++ b/sys/arch/m68k/include/pmap_motorola.h     Sun Dec 13 12:32:46 2009 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap_motorola.h,v 1.27 2009/12/11 18:57:44 tsutsui Exp $       */
+/*     $NetBSD: pmap_motorola.h,v 1.28 2009/12/13 12:32:46 tsutsui Exp $       */
 
 /* 
  * Copyright (c) 1991, 1993
@@ -101,8 +101,8 @@
  * We are using following segment layout in m68k pmap_motorola.c:
  * 68020/030 4KB/page: l1,l2,page    == 10,10,12       (%tc = 0x82c0aa00)
  * 68020/030 8KB/page: l1,l2,page    ==  8,11,13       (%tc = 0x82d08b00)
- * 68040/060 4KB/page: l1,l2,l3,page == 7,7,6,12
- * 68040/060 8KB/page: l1,l2,l3,page == 7,7,5,13
+ * 68040/060 4KB/page: l1,l2,l3,page == 7,7,6,12       (%tc = 0x8000)
+ * 68040/060 8KB/page: l1,l2,l3,page == 7,7,5,13       (%tc = 0xc000)
  *
  * 68020/030 l2 size is chosen per NPTEPG, a number of page table entries
  * per page, to use one whole page for PTEs per one segment table entry,
@@ -152,18 +152,20 @@
  * (block 31).  For convenience, the level 1 table is considered to be
  * block 0.
  *
- * MAX[KU]L2SIZE control how many pages of level 2 descriptors are allowed.
- * for the kernel and users.  8 implies only the initial "segment table"
- * page is used.  WARNING: don't change MAXUL2SIZE unless you can allocate
- * physically contiguous pages for the ST in pmap.c!
+ * MAX[KU]L2SIZE control how many pages of level 2 descriptors are allowed
+ * for the kernel and users.
+ * 16 or 8 implies only the initial "segment table" page is used,
+ * i.e. it means PAGE_SIZE / (SG4_LEV1SIZE * sizeof(st_entry_t)).
+ * WARNING: don't change MAXUL2SIZE unless you can allocate
+ * physically contiguous pages for the ST in pmap_motorola.c!
  */
 #define MAXKL2SIZE     32
-#if PAGE_SIZE == 8192
+#if PAGE_SIZE == 8192  /* NBPG / (SG4_LEV1SIZE * sizeof(st_entry_t)) */
 #define MAXUL2SIZE     16
 #else
 #define MAXUL2SIZE     8
 #endif
-#define l2tobm(n)      (1 << (n))
+#define l2tobm(n)      (1U << (n))
 #define bmtol2(n)      (ffs(n) - 1)
 
 /*