Re: [PATCH] common/cnxk: use cas with release semantics for batch alloc

[Ferruh Yigit <ferruh.yigit@intel.com>]

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 <asekhar@marvell.com>
>> ---
>>   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?