5.15-stable review patch. If anyone has any objections, please let me know.
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From: Maxime Chevallier maxime.chevallier@bootlin.com
[ 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@bootlin.com Link: https://patch.msgid.link/20241122141256.764578-1-maxime.chevallier@bootlin.c... Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 6b447d8f0bd8a..9c726fe40acdf 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;