Commit 05f9d3e1ae6e ("igb: Add support for CBS offload") restores the i210 Rx packet buffer size with an unmasked write to RXPBS. Bit 31 of RXPBS is CFG_TS_EN, which enables per-packet Rx timestamping. Writing the register unconditionally clears this bit on every igb_up() (link down/up, MTU change, or driver reset). Like other drivers (igc, i40e, ice), igb intends timestamping settings to persist across link changes: igb_reset() calls igb_ptp_reset() to re-apply tstamp_config and set CFG_TS_EN with queues stopped. igb_up() then clears it immediately afterwards, undoing its own restore. igb_ptp_hwtstamp_get() returns cached settings and never reads the register, masking the fallback to software timestamps. On an i210, a link flap increases PTP path delay from <1us to tens of microseconds. Fix by masking the buffer size field, as the FQTSS branch already does. Fixes: 05f9d3e1ae6e ("igb: Add support for CBS offload") Signed-off-by: Pascal Kneuper --- drivers/net/ethernet/intel/igb/igb_main.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c index d4a897a8c82c6..0f3c728a07fb1 100644 --- a/drivers/net/ethernet/intel/igb/igb_main.c +++ b/drivers/net/ethernet/intel/igb/igb_main.c @@ -1947,7 +1947,12 @@ static void igb_setup_tx_mode(struct igb_adapter *adapter) igb_config_tx_modes(adapter, i); } } else { - wr32(E1000_RXPBS, I210_RXPBSIZE_DEFAULT); + /* Preserve RXPBS.CFG_TS_EN so Rx timestamping settings + * persist across link changes. + */ + val = rd32(E1000_RXPBS) & E1000_RXPBS_CFG_TS_EN; + wr32(E1000_RXPBS, val | I210_RXPBSIZE_DEFAULT); + wr32(E1000_TXPBS, I210_TXPBSIZE_DEFAULT); wr32(E1000_I210_DTXMXPKTSZ, I210_DTXMXPKTSZ_DEFAULT); -- 2.47.3