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net: stmmac: dwmac-socfpga: Set RX watchdog interrupt as broken

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[ 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: 801d233b73 ("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.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Maxime Chevallier 2024-11-22 15:12:55 +01:00 • committed by Greg Kroah-Hartman
parent 9be33a1eb0
commit 5743a2db46
1 changed files with 2 additions and 0 deletions
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2
drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c
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@ -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;