iavf_read_phc_indirect(9)

💅 iavf_read_phc_indirect(9) 💅

okay bestie, welcome to the Kernel API Manual page for iavf_read_phc_indirect(9) 💖. Yes, the manual name is right here near the top, folded in all cute and official. This is the indirect PHC-time-read situation, and we’re gonna get through it together, no cap.

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🌸 NAME 🌸

iavf_read_phc_indirect — indirectly read the PHC time via virtchnl ✨

🦋 SYNOPSIS 🦋

int iavf_read_phc_indirect (struct iavf_adapter *adapter , struct
       timespec64 *ts , struct ptp_system_timestamp *sts );

🎀 ARGUMENTS 🎀

• adapter — private adapter structure; this is the main-character struct we’re working with 🫶
• ts — storage for the timestamp value; the timestamp goes here 💖
• sts — system timestamp values before and after the read; it’s literally the before-and-after system timestamps 🎀

🌈 DESCRIPTION 🌈

okay so here’s the whole vibe: this function is used when the device does not have direct register access to the PHC time. Instead, it indirectly reads the time via VIRTCHNL_OP_1588_PTP_GET_TIME, and waits for the reply from the PF. The way that indirect read has to wait for the PF reply? it’s giving “hold on, bestie” energy 💅.

Based on some simple measurements using ftrace and phc2sys, this clock access method has about a ~110 usec latency even when the system is not under load. That’s ~110 usec of latency, bestie — highkey important to know 😭.

In order to achieve acceptable results when using phc2sys with the indirect clock access method, it is recommended to use more conservative proportional and integration constants with the P/I servo. This is a real recommendation, not a vibe-only suggestion — conservative constants with the P/I servo, fr fr 🫶.

⭐ RETURN ⭐

0 if success, error code otherwise. That’s the whole return deal. Periodt. 💖

🔥 SEE ALSO 🔥

Kernel file: ./drivers/net/ethernet/intel/iavf/iavf_ptp.c

The whole friend group:

• iavf_ptp_disable_rx_tstamp(9)
• iavf_ptp_enable_rx_tstamp(9)
• iavf_ptp_set_timestamp_mode(9)
• iavf_ptp_set_ts_config(9)
• iavf_ptp_cap_supported(9)
• iavf_allocate_ptp_cmd(9)
• iavf_queue_ptp_cmd(9)
• iavf_send_phc_read(9)
• iavf_ptp_cache_phc_time(9)
• iavf_ptp_do_aux_work(9)
• iavf_ptp_register_clock(9)
• iavf_ptp_init(9)
• iavf_ptp_release(9)
• iavf_ptp_process_caps(9)
• iavf_ptp_extend_32b_timestamp(9)

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🫶 cute sign-off time: source/version is ./drivers/net/ethernet/intel/iavf, the date is October 2026, and this was iavf_read_phc_indirect(9) from the Kernel API Manual. bye bestie, go read that PHC time indirectly 💜