On 06/07/26 13:57, Nikhil Kumar Singh wrote:
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 <[email protected]>
---
arch/powerpc/kernel/head_64.S | 20 ++++++++++++--------
1 file 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 */
Makes sense. Feel free to keep the rb.
Reviewed-by: Aditya Gupta <[email protected]>
Thanks,
- Aditya G
