Re: [PATCH 2/4] net: ionic: Add PHC state page for user space access

[Allen Hubbe <allen.hubbe@amd.com>]

On 4/1/2026 8:06 PM, Jakub Kicinski wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> 
> 
> On Wed, 1 Apr 2026 15:54:59 +0530 Abhijit Gangurde wrote:
>> diff --git a/include/uapi/rdma/ionic-abi.h b/include/uapi/rdma/ionic-abi.h
>> index 7b589d3e9728..97f695510380 100644
>> --- a/include/uapi/rdma/ionic-abi.h
>> +++ b/include/uapi/rdma/ionic-abi.h
>> @@ -112,4 +112,15 @@ struct ionic_srq_resp {
>>        __aligned_u64 rq_cmb_offset;
>>   };
>>
>> +struct ionic_phc_state {
>> +     __u32 seq;
>> +     __u32 rsvd;
>> +     __aligned_u64 mask;
>> +     __aligned_u64 tick;
>> +     __aligned_u64 nsec;
>> +     __aligned_u64 frac;
>> +     __u32 mult;
>> +     __u32 shift;
>> +};
> 
> You're just exposing kernel timecounter internals.
> Why is this ionic uAPI and not something reusable by other drivers?

The simple answer is just following the same approach as an existing 
implementation.  See struct mlx5_ib_clock_info and 
mlx5_update_clock_info_page().

Making this common might risk presuming that other implementations will 
be a similar design.  Compare these to the sfc driver.  The clock is 
quite different from ionic and mlx5, not using timecounter, because 
instead of a free-running cycle counter the hardware itself provides an 
adjustable clock for timestamping.