[src/trunk]: src/sys/arch/arm/arm32 Add an XSCALE_CACHE_READ_WRITE_ALLOCATE o...

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

details:   https://anonhg.NetBSD.org/src/rev/c4ed5b05f4c7
branches:  trunk
changeset: 535076:c4ed5b05f4c7
user:      thorpej <thorpej%NetBSD.org@localhost>
date:      Fri Aug 09 21:49:09 2002 +0000

description:
Add an XSCALE_CACHE_READ_WRITE_ALLOCATE option for people who
want to play fast-and-loose.

diffstat:

 sys/arch/arm/arm32/pmap.c |  23 +++++++++++++++++++++--
 1 files changed, 21 insertions(+), 2 deletions(-)

diffs (44 lines):

diff -r f35ecfc9c9de -r c4ed5b05f4c7 sys/arch/arm/arm32/pmap.c
--- a/sys/arch/arm/arm32/pmap.c Fri Aug 09 18:22:59 2002 +0000
+++ b/sys/arch/arm/arm32/pmap.c Fri Aug 09 21:49:09 2002 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap.c,v 1.105 2002/08/09 18:22:59 thorpej Exp $       */
+/*     $NetBSD: pmap.c,v 1.106 2002/08/09 21:49:09 thorpej Exp $       */
 
 /*
  * Copyright (c) 2002 Wasabi Systems, Inc.
@@ -143,7 +143,7 @@
 #include <machine/param.h>
 #include <arm/arm32/katelib.h>
 
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.105 2002/08/09 18:22:59 thorpej Exp $");        
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.106 2002/08/09 21:49:09 thorpej Exp $");        
 #ifdef PMAP_DEBUG
 #define        PDEBUG(_lev_,_stat_) \
        if (pmap_debug_level >= (_lev_)) \
@@ -3848,6 +3848,25 @@
        pte_l2_s_cache_mode = L2_B|L2_C;
        pte_l2_s_cache_mask = L2_S_CACHE_MASK_xscale;
 
+#ifdef XSCALE_CACHE_READ_WRITE_ALLOCATE
+       /*
+        * The XScale core has an enhanced mode where writes that
+        * miss the cache cause a cache line to be allocated.  This
+        * is significantly faster than the traditional, write-through
+        * behavior of this case.
+        *
+        * However, there is a bug lurking in this pmap module, or in
+        * other parts of the VM system, or both, which causes corruption
+        * of NFS-backed files when this cache mode is used.  We have
+        * an ugly work-around for this problem (disable r/w-allocate
+        * for managed kernel mappings), but the bug is still evil enough
+        * to consider this cache mode "experimental".
+        */
+       pte_l1_s_cache_mode |= L1_S_XSCALE_TEX(TEX_XSCALE_X);
+       pte_l2_l_cache_mode |= L2_XSCALE_L_TEX(TEX_XSCALE_X);
+       pte_l2_s_cache_mode |= L2_XSCALE_T_TEX(TEX_XSCALE_X);
+#endif /* XSCALE_CACHE_READ_WRITE_ALLOCATE */
+
 #ifdef XSCALE_CACHE_WRITE_THROUGH
        /*
         * Some versions of the XScale core have various bugs in