5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>
[ Upstream commit 407618d66dba55e7db1278872e8be106808bbe91 ]
On DWMAC3 and later, there's a RX Watchdog interrupt that's used for
interrupt coalescing. It's known to be buggy on some platforms, and
dwmac-socfpga appears to be one of them. Changing the interrupt
coalescing from ethtool doesn't appear to have any effect here.
Without disabling RIWT (Received Interrupt Watchdog Timer, I
believe...), we observe latencies while receiving traffic that amount to
around ~0.4ms. This was discovered with NTP but can be easily reproduced
with a simple ping. Without this patch :
64 bytes from 192.168.5.2: icmp_seq=1 ttl=64 time=0.657 ms
With this patch :
64 bytes from 192.168.5.2: icmp_seq=1 ttl=64 time=0.254 ms
Fixes: 801d233b7302 ("net: stmmac: Add SOCFPGA glue driver")
Signed-off-by: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>
Link: https://patch.msgid.link/20241122141256.764578-1-maxime.chevallier@xxxxxxxxxxx
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c
index 934c34e98d55f..0333c97c2b995 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c
@@ -426,6 +426,8 @@ static int socfpga_dwmac_probe(struct platform_device *pdev)
plat_dat->bsp_priv = dwmac;
plat_dat->fix_mac_speed = socfpga_dwmac_fix_mac_speed;
+ plat_dat->riwt_off = 1;
+
ret = stmmac_dvr_probe(&pdev->dev, plat_dat, &stmmac_res);
if (ret)
goto err_remove_config_dt;
--
2.43.0
