There is a possibility that the context descriptor still owned by the DMA even the previous normal descriptor own bit is already cleared. Checking the context descriptor readiness without delay might be not enough time for the DMA to update the descriptor field, which causing failure in getting HW Rx timestamp.
This patch introduces a 1us fsleep() in HW Rx timestamp checking loop to give time for DMA to update/complete the context descriptor.
ptp4l Timestamp log without this patch: ----------------------------------------------------------- $ echo 10000 > /sys/class/net/enp0s30f4/gro_flush_timeout $ echo 10000 > /sys/class/net/enp0s30f4/napi_defer_hard_irqs $ ptp4l -P2Hi enp0s30f4 --step_threshold=1 -m ptp4l: selected /dev/ptp2 as PTP clock ptp4l: port 1: INITIALIZING to LISTENING on INIT_COMPLETE ptp4l: selected local clock 901210.fffe.b57df7 as best master ptp4l: port 1: new foreign master 22bb22.fffe.bb22bb-1 ptp4l: selected best master clock 22bb22.fffe.bb22bb ptp4l: port 1: LISTENING to UNCALIBRATED on RS_SLAVE ptp4l: port 1: UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED ptp4l: port 1: received SYNC without timestamp ptp4l: rms 49 max 63 freq -9573 +/- 34 delay 71 +/- 1 ptp4l: rms 15 max 25 freq -9553 +/- 20 delay 72 +/- 0 ptp4l: port 1: received SYNC without timestamp ptp4l: rms 9 max 18 freq -9540 +/- 11 delay 70 +/- 0 ptp4l: port 1: received PDELAY_REQ without timestamp ptp4l: rms 16 max 29 freq -9519 +/- 12 delay 72 +/- 0 ptp4l: port 1: received PDELAY_REQ without timestamp ptp4l: rms 9 max 18 freq -9527 +/- 12 delay 72 +/- 0 ptp4l: rms 5 max 9 freq -9530 +/- 7 delay 70 +/- 0 ptp4l: rms 11 max 20 freq -9530 +/- 16 delay 72 +/- 0 ptp4l: rms 5 max 11 freq -9530 +/- 7 delay 74 +/- 0 ptp4l: rms 6 max 9 freq -9522 +/- 7 delay 72 +/- 0 ptp4l: port 1: received PDELAY_REQ without timestamp -----------------------------------------------------------
ptp4l Timestamp log with this patch: ----------------------------------------------------------- $ echo 10000 > /sys/class/net/enp0s30f4/gro_flush_timeout $ echo 10000 > /sys/class/net/enp0s30f4/napi_defer_hard_irqs $ ptp4l -P2Hi enp0s30f4 --step_threshold=1 -m ptp4l: selected /dev/ptp2 as PTP clock ptp4l: port 1: INITIALIZING to LISTENING on INIT_COMPLETE ptp4l: selected local clock 901210.fffe.b57df7 as best master ptp4l: port 1: new foreign master 22bb22.fffe.bb22bb-1 ptp4l: selected best master clock 22bb22.fffe.bb22bb ptp4l: port 1: LISTENING to UNCALIBRATED on RS_SLAVE ptp4l: port 1: UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED ptp4l: rms 30 max 45 freq -9400 +/- 23 delay 72 +/- 0 ptp4l: rms 7 max 16 freq -9414 +/- 10 delay 70 +/- 0 ptp4l: rms 6 max 9 freq -9422 +/- 6 delay 72 +/- 0 ptp4l: rms 13 max 20 freq -9436 +/- 13 delay 74 +/- 0 ptp4l: rms 12 max 27 freq -9446 +/- 11 delay 72 +/- 0 ptp4l: rms 9 max 12 freq -9453 +/- 6 delay 74 +/- 0 ptp4l: rms 9 max 15 freq -9438 +/- 11 delay 74 +/- 0 ptp4l: rms 10 max 16 freq -9435 +/- 12 delay 74 +/- 0 ptp4l: rms 8 max 18 freq -9428 +/- 8 delay 72 +/- 0 ptp4l: rms 8 max 18 freq -9423 +/- 8 delay 72 +/- 0 ptp4l: rms 9 max 16 freq -9431 +/- 12 delay 70 +/- 0 ptp4l: rms 9 max 18 freq -9441 +/- 9 delay 72 +/- 0 -----------------------------------------------------------
Fixes: ba1ffd74df74 ("stmmac: fix PTP support for GMAC4") Cc: stable@vger.kernel.org # 5.4.x Signed-off-by: Song Yoong Siang yoong.siang.song@intel.com Signed-off-by: Tan Tee Min tee.min.tan@intel.com --- drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c index d3b4765c1a5b..289bf26a6105 100644 --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c @@ -279,10 +279,11 @@ static int dwmac4_wrback_get_rx_timestamp_status(void *desc, void *next_desc, /* Check if timestamp is OK from context descriptor */ do { ret = dwmac4_rx_check_timestamp(next_desc); - if (ret < 0) + if (ret <= 0) goto exit; i++;
+ fsleep(1); } while ((ret == 1) && (i < 10));
if (i == 10)