diff options
| author | Nikhil Kumar Singh <nikhilks@linux.ibm.com> | 2026-07-06 13:57:08 +0530 |
|---|---|---|
| committer | Madhavan Srinivasan <maddy@linux.ibm.com> | 2026-08-03 14:49:17 +0530 |
| commit | 76ea1257924f64521f708db91c99014ce7249bbf (patch) | |
| tree | 9a4a62883bee7b24b591dba1f53b62b41f528b54 | |
| parent | 00be69070d91d2be978e752bb117a0a4db0e1281 (diff) | |
powerpc/64s: Clarify copy_and_flush() cache sync loop comment
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 <nikhilks@linux.ibm.com>
Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Reviewed-by: Aditya Gupta <adityag@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260706082708.43918-1-nikhilks@linux.ibm.com
| -rw-r--r-- | arch/powerpc/kernel/head_64.S | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S index 63432a33ec49..a54f6f979173 100644 --- a/arch/powerpc/kernel/head_64.S +++ b/arch/powerpc/kernel/head_64.S @@ -713,14 +713,18 @@ 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 may skip */ + /* dcbst/icbi for lines in between and */ + /* leave stale instructions in icache. */ + /* 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. */ mtctr r0 /* put # words/line in ctr */ 3: addi r6,r6,8 /* copy a cache line */ |