net: ionic: Add PHC state page for user space access

Add a page associated with the PHC that can be mapped to user space,
allowing applications to access hardware timestamp information.

In order to synchronize between kernel and user space, a sequence
number is incremented at the beginning and end of each update.
An odd number means the data is being updated while an even number
means the update is complete. To guarantee that the data structure
was accessed atomically, user space will:

repeat:
        seq1 = <read sequence>
        goto <repeat> if odd
        <read PHC state>
        seq2 = <read sequence>
        if seq1 != seq2 goto repeat

This mechanism acts as a guard against reading invalid state during
concurrent updates.

Co-developed-by: Allen Hubbe <allen.hubbe@amd.com>
Signed-off-by: Allen Hubbe <allen.hubbe@amd.com>
Signed-off-by: Abhijit Gangurde <abhijit.gangurde@amd.com>
Link: https://patch.msgid.link/20260610154216.712374-3-abhijit.gangurde@amd.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>

0 files changed, 0 insertions, 0 deletions