[PATCH] powerpc/64s: Clarify copy_and_flush() cache sync loop comment
From: Nikhil Kumar Singh <hidden>
Date: 2026-07-01 18:28:30
Also in:
lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
The value loaded into r0 in copy_and_flush() represents the number of 8-byte words processed between cache synchronization operations. The existing comment refers to cache line size, which can make it appear that the value is a cache line size in bytes rather than a loop count. Clarify the comment to explain that the loop processes 8 words (64 bytes) per cache synchronization iteration, and that increasing the value would skip cache maintenance for intermediate cache lines. This is a comment-only change with no functional impact. Signed-off-by: Nikhil Kumar Singh <redacted> --- arch/powerpc/kernel/head_64.S | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 63432a33ec49..e21c2bce8f7e 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S@@ -713,14 +713,14 @@ p_end: .8byte _end - copy_to_here _GLOBAL(copy_and_flush) addi r5,r5,-8 addi r6,r6,-8 -4: li r0,8 /* Use the smallest common */ - /* denominator cache line */ - /* size. This results in */ - /* extra cache line flushes */ - /* but operation is correct. */ - /* Can't get cache line size */ - /* from NACA as it is being */ - /* moved too. */ +4: li r0,8 /* r0 is the number of 8-byte words */ + /* to copy per cache sync iteration. */ + /* 8 words * 8 bytes = 64 bytes. 64B is */ + /* the current default cache line size. */ + /* This is a loop count, not a byte */ + /* count. Increasing it will skip */ + /* dcbst/icbi for lines in between and */ + /* leave stale instructions in icache. */ mtctr r0 /* put # words/line in ctr */ 3: addi r6,r6,8 /* copy a cache line */
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2.43.5