diff --git a/drivers/net/ethernet/intel/igc/igc_ptp.c b/drivers/net/ethernet/intel/igc/igc_ptp.c index cf963a12a92fe..32ef112f8291a 100644 --- a/drivers/net/ethernet/intel/igc/igc_ptp.c +++ b/drivers/net/ethernet/intel/igc/igc_ptp.c @@ -685,14 +685,49 @@ static void igc_ptp_tx_hwtstamp(struct igc_adapter *adapter) struct sk_buff *skb = adapter->ptp_tx_skb; struct skb_shared_hwtstamps shhwtstamps; struct igc_hw *hw = &adapter->hw; + u32 tsynctxctl; int adjust = 0; u64 regval; if (WARN_ON_ONCE(!skb)) return; - regval = rd32(IGC_TXSTMPL); - regval |= (u64)rd32(IGC_TXSTMPH) << 32; + tsynctxctl = rd32(IGC_TSYNCTXCTL); + tsynctxctl &= IGC_TSYNCTXCTL_TXTT_0; + if (tsynctxctl) { + regval = rd32(IGC_TXSTMPL); + regval |= (u64)rd32(IGC_TXSTMPH) << 32; + } else { + /* There's a bug in the hardware that could cause + * missing interrupts for TX timestamping. The issue + * is that for new interrupts to be triggered, the + * IGC_TXSTMPH_0 register must be read. + * + * To avoid discarding a valid timestamp that just + * happened at the "wrong" time, we need to confirm + * that there was no timestamp captured, we do that by + * assuming that no two timestamps in sequence have + * the same nanosecond value. + * + * So, we read the "low" register, read the "high" + * register (to latch a new timestamp) and read the + * "low" register again, if "old" and "new" versions + * of the "low" register are different, a valid + * timestamp was captured, we can read the "high" + * register again. + */ + u32 txstmpl_old, txstmpl_new; + + txstmpl_old = rd32(IGC_TXSTMPL); + rd32(IGC_TXSTMPH); + txstmpl_new = rd32(IGC_TXSTMPL); + + if (txstmpl_old == txstmpl_new) + return; + + regval = txstmpl_new; + regval |= (u64)rd32(IGC_TXSTMPH) << 32; + } if (igc_ptp_systim_to_hwtstamp(adapter, &shhwtstamps, regval)) return; @@ -730,22 +765,13 @@ static void igc_ptp_tx_hwtstamp(struct igc_adapter *adapter) */ void igc_ptp_tx_tstamp_event(struct igc_adapter *adapter) { - struct igc_hw *hw = &adapter->hw; unsigned long flags; - u32 tsynctxctl; spin_lock_irqsave(&adapter->ptp_tx_lock, flags); if (!adapter->ptp_tx_skb) goto unlock; - tsynctxctl = rd32(IGC_TSYNCTXCTL); - tsynctxctl &= IGC_TSYNCTXCTL_TXTT_0; - if (!tsynctxctl) { - WARN_ONCE(1, "Received a TSTAMP interrupt but no TSTAMP is ready.\n"); - goto unlock; - } - igc_ptp_tx_hwtstamp(adapter); unlock: