> -----Original Message----- > From: Pascal Kneuper <[email protected]> > Sent: Thursday, September 10, 2026 4:39 AM > To: Nguyen, Anthony L <[email protected]>; Kitszel, Przemyslaw > <[email protected]>; Andrew Lunn <[email protected]>; David S > . Miller <[email protected]>; Eric Dumazet <[email protected]>; Jakub > Kicinski <[email protected]>; Paolo Abeni <[email protected]> > Cc: Baldin, Daniel <[email protected]>; [email protected]; > [email protected]; [email protected]; Kneuper, Paskal > <[email protected]> > Subject: [PATCH net 1/2] igb: Preserve RXPBS.CFG_TS_EN in igb_setup_tx_mode > > 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 <[email protected]> > --- > drivers/net/ethernet/intel/igb/igb_main.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-)
Tested-by: Alexander Nowlin <[email protected]>
