On 1/11/2022 12:26 PM, Ashwin Sekhar Thalakalath Kottilveetil wrote:
CAS is compare and swap. CASL is compare and swap with release semantics.
What does 'release semantics' mean? What is functional difference in both?
But on CNXK platform, the functionality of CAS* instructions is completely
different when it is done to specific addresses. These APIs are meant for use
for such special cases. These cannot be made ARM generic.
Ashwin Sekhar T K
-----Original Message-----
From: Ferruh Yigit <[email protected]>
Sent: Tuesday, January 11, 2022 5:42 PM
To: Ashwin Sekhar Thalakalath Kottilveetil <[email protected]>;
[email protected]; Honnappa Nagarahalli <[email protected]>;
Ruifeng Wang (Arm Technology China) <[email protected]>
Cc: Nithin Kumar Dabilpuram <[email protected]>; Jerin Jacob
Kollanukkaran <[email protected]>; Sunil Kumar Kori
<[email protected]>; Satha Koteswara Rao Kottidi
<[email protected]>; Pavan Nikhilesh Bhagavatula
<[email protected]>; Kiran Kumar Kokkilagadda
<[email protected]>; Satheesh Paul <[email protected]>;
Anoob Joseph <[email protected]>; Akhil Goyal <[email protected]>
Subject: [EXT] Re: [PATCH] common/cnxk: use cas with release semantics for
batch alloc
External Email
----------------------------------------------------------------------
On 1/11/2022 12:08 PM, Ferruh Yigit wrote:
On 11/30/2021 5:45 AM, Ashwin Sekhar T K wrote:
Before issuing the batch alloc, we clear the first word of cache
lines so that NPA can update the status. Make sure that this line
clear is flushed before the batch alloc is issued.
Signed-off-by: Ashwin Sekhar T K <[email protected]>
---
drivers/common/cnxk/roc_io.h | 12 ++++++++++++
drivers/common/cnxk/roc_io_generic.h | 9 +++++++++
drivers/common/cnxk/roc_npa.h | 2 +-
3 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/drivers/common/cnxk/roc_io.h
b/drivers/common/cnxk/roc_io.h index fe5f7f46d0..4f15503c29 100644
--- a/drivers/common/cnxk/roc_io.h
+++ b/drivers/common/cnxk/roc_io.h
@@ -78,6 +78,18 @@ roc_atomic64_cas(uint64_t compare, uint64_t
swap,
int64_t *ptr)
return compare;
}
+static __plt_always_inline uint64_t
+roc_atomic64_casl(uint64_t compare, uint64_t swap, int64_t *ptr) {
+ asm volatile(PLT_CPU_FEATURE_PREAMBLE
+ "casl %[compare], %[swap], [%[ptr]]\n"
+ : [compare] "+r"(compare)
+ : [swap] "r"(swap), [ptr] "r"(ptr)
+ : "memory");
+
out of curiosity, what is the "cas with release semantics"?
briefly, what is the difference between 'cas' and 'casl'?
+ Honnappa & Ruifeng,
Isn't this API Arm wide, instead of being cnxk specific?
Does it make sense to make this API for arm and cnxk use from there?
