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Fixed HW timestamping of RX UDP P2P packets. #58

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Fixed HW timestamping of RX UDP P2P packets. #58

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16 changes: 13 additions & 3 deletions hw_atl/hw_atl_b0.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1481,9 +1481,19 @@ static u16 hw_atl_b0_rx_extract_ts(struct aq_hw_s *self, u8 *p,
*timestamp = (be64_to_cpu(sec) & 0xffffffffffffllu) * NSEC_PER_SEC +
be32_to_cpu(ns) + self->ptp_clk_offset;

eth = (struct ethhdr *)p;

return (eth->h_proto == htons(ETH_P_1588)) ? 12 : 14;
return 12;
// This is super weird. It seems that the timestamps occupy the last 14
// bytes, but for some reason, the packet is only extended by 12 bytes.
// No idea what happens to the last 2 bytes of the payload, but it is
// probably wrong (fortunately, there's hopefully not too much interesting
// data there in the timestamped PTP packets, and the first 2 bytes of sec
// will always be 00 00, so basically the last 2 bytes will get zeroed out).
// Following is an even weirder construct that used to be in the driver,
// giving some proof that removing just 12 of the 14 bytes is not a complete
// nonsense. However, in my experience, both L2 and UDP packets suffer from
// this weirdness.
//eth = (struct ethhdr *)p;
//return (eth->h_proto == htons(ETH_P_1588)) ? 12 : 14;
}

static int hw_atl_b0_extract_hwts(struct aq_hw_s *self, u8 *p, unsigned int len,
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