In the current implementation, IP coalescing is always enabled and cannot be disabled. As setting maximum frames to 0 or 1, or setting delay to zero implies immediate delivery of single packets/IRQs, disable coalescing in hardware in these cases. This also guarantees that coalescing is never enabled with ICFT or ICTT set to zero, a configuration that could lead to unpredictable behaviour according to i.MX8MP reference manual. Signed-off-by: Jonas Rebmann --- Changes in v2: - Adjust type of rx_itr, tx_itr (Thanks, Wei) - Set multiple FEC_ITR_ flags in one line for more compact code (Thanks, Wei) - Commit Message: mention ICFT/CTT fields constraints (Thanks, Andrew) - Link to v1: https://lore.kernel.org/r/20250625-fec_deactivate_coalescing-v1-1-57a1e41a45d3@pengutronix.de --- drivers/net/ethernet/freescale/fec_main.c | 34 +++++++++++++++---------------- 1 file changed, 16 insertions(+), 18 deletions(-) diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c index 63dac42720453a8b8a847bdd1eec76ac072030bf..d4eed252ad4098a7962f615bce98338bc3d12f5c 100644 --- a/drivers/net/ethernet/freescale/fec_main.c +++ b/drivers/net/ethernet/freescale/fec_main.c @@ -3121,27 +3121,25 @@ static int fec_enet_us_to_itr_clock(struct net_device *ndev, int us) static void fec_enet_itr_coal_set(struct net_device *ndev) { struct fec_enet_private *fep = netdev_priv(ndev); - int rx_itr, tx_itr; + u32 rx_itr = 0, tx_itr = 0; + int rx_ictt, tx_ictt; - /* Must be greater than zero to avoid unpredictable behavior */ - if (!fep->rx_time_itr || !fep->rx_pkts_itr || - !fep->tx_time_itr || !fep->tx_pkts_itr) - return; - - /* Select enet system clock as Interrupt Coalescing - * timer Clock Source - */ - rx_itr = FEC_ITR_CLK_SEL; - tx_itr = FEC_ITR_CLK_SEL; + rx_ictt = fec_enet_us_to_itr_clock(ndev, fep->rx_time_itr); + tx_ictt = fec_enet_us_to_itr_clock(ndev, fep->tx_time_itr); - /* set ICFT and ICTT */ - rx_itr |= FEC_ITR_ICFT(fep->rx_pkts_itr); - rx_itr |= FEC_ITR_ICTT(fec_enet_us_to_itr_clock(ndev, fep->rx_time_itr)); - tx_itr |= FEC_ITR_ICFT(fep->tx_pkts_itr); - tx_itr |= FEC_ITR_ICTT(fec_enet_us_to_itr_clock(ndev, fep->tx_time_itr)); + if (rx_ictt > 0 && fep->rx_pkts_itr > 1) { + /* Enable with enet system clock as Interrupt Coalescing timer Clock Source */ + rx_itr = FEC_ITR_EN | FEC_ITR_CLK_SEL; + rx_itr |= FEC_ITR_ICFT(fep->rx_pkts_itr); + rx_itr |= FEC_ITR_ICTT(rx_ictt); + } - rx_itr |= FEC_ITR_EN; - tx_itr |= FEC_ITR_EN; + if (tx_ictt > 0 && fep->tx_pkts_itr > 1) { + /* Enable with enet system clock as Interrupt Coalescing timer Clock Source */ + tx_itr = FEC_ITR_EN | FEC_ITR_CLK_SEL; + tx_itr |= FEC_ITR_ICFT(fep->tx_pkts_itr); + tx_itr |= FEC_ITR_ICTT(tx_ictt); + } writel(tx_itr, fep->hwp + FEC_TXIC0); writel(rx_itr, fep->hwp + FEC_RXIC0); --- base-commit: 8dacfd92dbefee829ca555a860e86108fdd1d55b change-id: 20250625-fec_deactivate_coalescing-c6f8d14a1d66 Best regards, -- Jonas Rebmann