powerpc/pseries: Improve stream generation comments in copypage/user

No code changes, just documenting what's happening a little better.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 11 insertions, 8 deletions

diff --git a/arch/powerpc/lib/copypage_power7.S b/arch/powerpc/lib/copypage_power7.S
index 0ef75bf0695c..395c594722a2 100644
--- a/arch/powerpc/lib/copypage_power7.S
+++ b/arch/powerpc/lib/copypage_power7.S
@@ -28,13 +28,14 @@ _GLOBAL(copypage_power7)
          * aligned we don't need to clear the bottom 7 bits of either
          * address.
          */
-        ori     r9,r3,1         /* stream=1 */
+        ori     r9,r3,1         /* stream=1 => to */
 
 #ifdef CONFIG_PPC_64K_PAGES
-        lis     r7,0x0E01       /* depth=7, units=512 */
+        lis     r7,0x0E01       /* depth=7
+                                 * units/cachelines=512 */
 #else
         lis     r7,0x0E00       /* depth=7 */
-        ori     r7,r7,0x1000    /* units=32 */
+        ori     r7,r7,0x1000    /* units/cachelines=32 */
 #endif
         ori     r10,r7,1        /* stream=1 */
 
@@ -43,12 +44,14 @@ _GLOBAL(copypage_power7)
 
 .machine push
 .machine "power4"
-        dcbt    r0,r4,0b01000
-        dcbt    r0,r7,0b01010
-        dcbtst  r0,r9,0b01000
-        dcbtst  r0,r10,0b01010
+        /* setup read stream 0  */
+        dcbt    r0,r4,0b01000   /* addr from */
+        dcbt    r0,r7,0b01010   /* length and depth from */
+        /* setup write stream 1 */
+        dcbtst  r0,r9,0b01000   /* addr to */
+        dcbtst  r0,r10,0b01010  /* length and depth to */
         eieio
-        dcbt    r0,r8,0b01010   /* GO */
+        dcbt    r0,r8,0b01010   /* all streams GO */
 .machine pop
 
 #ifdef CONFIG_ALTIVEC