Merge master.kernel.org:/pub/scm/linux/kernel/git/gregkh/pci-2.6

* master.kernel.org:/pub/scm/linux/kernel/git/gregkh/pci-2.6: (169 commits)
  commit 78a596b4490e17b9990d87b9d468ef5bb70daa10
  Author: Adrian Bunk <bunk@stusta.de>
  Date:   Fri Mar 31 01:38:12 2006 -0800
  
      [PATCH] remove kernel/power/pm.c:pm_unregister()
      
      Since the last user is removed in -mm, we can now remove this long deprecated
      function.
      
      Signed-off-by: Adrian Bunk <bunk@stusta.de>
      Cc: Pavel Machek <pavel@ucw.cz>
      Signed-off-by: Andrew Morton <akpm@osdl.org>
      Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  
  commit 21440d313358043b0ce5e43b00ff3c9b35a8616c
  Author: David Brownell <david-b@pacbell.net>
  Date:   Sat Apr 1 10:21:52 2006 -0800
  
      [PATCH] dma doc updates
      
  ...

1 files changed, 17 insertions, 5 deletions

diff --git a/Documentation/DMA-mapping.txt b/Documentation/DMA-mapping.txt
index 10bf4deb96a..7c717699032 100644
--- a/Documentation/DMA-mapping.txt
+++ b/Documentation/DMA-mapping.txt
@@ -58,11 +58,15 @@ translating each of those pages back to a kernel address using
 something like __va().  [ EDIT: Update this when we integrate
 Gerd Knorr's generic code which does this. ]
 
-This rule also means that you may not use kernel image addresses
-(ie. items in the kernel's data/text/bss segment, or your driver's)
-nor may you use kernel stack addresses for DMA.  Both of these items
-might be mapped somewhere entirely different than the rest of physical
-memory.
+This rule also means that you may use neither kernel image addresses
+(items in data/text/bss segments), nor module image addresses, nor
+stack addresses for DMA.  These could all be mapped somewhere entirely
+different than the rest of physical memory.  Even if those classes of
+memory could physically work with DMA, you'd need to ensure the I/O
+buffers were cacheline-aligned.  Without that, you'd see cacheline
+sharing problems (data corruption) on CPUs with DMA-incoherent caches.
+(The CPU could write to one word, DMA would write to a different one
+in the same cache line, and one of them could be overwritten.)
 
 Also, this means that you cannot take the return of a kmap()
 call and DMA to/from that.  This is similar to vmalloc().
@@ -284,6 +288,11 @@ There are two types of DMA mappings:
 
              in order to get correct behavior on all platforms.
 
+	     Also, on some platforms your driver may need to flush CPU write
+	     buffers in much the same way as it needs to flush write buffers
+	     found in PCI bridges (such as by reading a register's value
+	     after writing it).
+
 - Streaming DMA mappings which are usually mapped for one DMA transfer,
   unmapped right after it (unless you use pci_dma_sync_* below) and for which
   hardware can optimize for sequential accesses.
@@ -303,6 +312,9 @@ There are two types of DMA mappings:
 
 Neither type of DMA mapping has alignment restrictions that come
 from PCI, although some devices may have such restrictions.
+Also, systems with caches that aren't DMA-coherent will work better
+when the underlying buffers don't share cache lines with other data.
+
 
 		 Using Consistent DMA mappings.