ramips: gsw_mt7621: disable PORT 5 MAC RX/TX flow control by default

Looking at the current upstream driver implementation, it seems like the
TX/RX flow control is enabled only if the flow control pause option is
resolved from the device/link partner advertisements (or otherwise set).

On the other hand, our current in-tree driver force enables TX/RX
flow control by default, thus possibly leading to TX timeouts if the
other end sends pause frames (which are not properly handled?):

 WARNING: CPU: 3 PID: 0 at net/sched/sch_generic.c:320 dev_watchdog+0x1ac/0x324
 NETDEV WATCHDOG: eth0 (mtk_soc_eth): transmit queue 0 timed out

Disabling the flow control on PORT 5 MAC seems to fix this issues as the
pause frames are then filtered out. While at it, I'm removing the if
condition completely as suggested, since this code is run only on mt7621
SoC, so there is no need to check for the silicon revisions.

Ref: https://lists.openwrt.org/pipermail/openwrt-devel/2017-November/009882.html
Ref: https://forum.openwrt.org/t/mtk-soc-eth-watchdog-timeout-after-r11573/50000/12
Suggested-by: Felix Fietkau <nbd@nbd.name>
Reported-by: Rosen Penev <rosenp@gmail.com>
Signed-off-by: Petr Štetiar <ynezz@true.cz>

diff --git a/target/linux/ramips/files-4.14/drivers/net/ethernet/mediatek/gsw_mt7621.c b/target/linux/ramips/files-4.14/drivers/net/ethernet/mediatek/gsw_mt7621.c
index 89be23900738095a8180532d5dd7e585f01bb7c4..232bcd8cf4ea5edbd34d815032ce72b1f1f85661 100644 (file)
--- a/target/linux/ramips/files-4.14/drivers/net/ethernet/mediatek/gsw_mt7621.c
+++ b/target/linux/ramips/files-4.14/drivers/net/ethernet/mediatek/gsw_mt7621.c
@@ -98,15 +98,9 @@ static void mt7621_hw_init(struct mt7620_gsw *gsw, struct device_node *np)
        mt7530_mdio_w32(gsw, 0x7000, 0x3);
        usleep_range(10, 20);
 
-       if ((rt_sysc_r32(SYSC_REG_CHIP_REV_ID) & 0xFFFF) == 0x0101) {
-               /* (GE1, Force 1000M/FD, FC ON, MAX_RX_LENGTH 1536) */
-               mtk_switch_w32(gsw, 0x2305e30b, GSW_REG_MAC_P0_MCR);
-               mt7530_mdio_w32(gsw, 0x3600, 0x5e30b);
-       } else {
-               /* (GE1, Force 1000M/FD, FC ON, MAX_RX_LENGTH 1536) */
-               mtk_switch_w32(gsw, 0x2305e33b, GSW_REG_MAC_P0_MCR);
-               mt7530_mdio_w32(gsw, 0x3600, 0x5e33b);
-       }
+       /* (GE1, Force 1000M/FD, FC OFF, MAX_RX_LENGTH 1536) */
+       mtk_switch_w32(gsw, 0x2305e30b, GSW_REG_MAC_P0_MCR);
+       mt7530_mdio_w32(gsw, 0x3600, 0x5e30b);
 
        /* (GE2, Link down) */
        mtk_switch_w32(gsw, 0x8000, GSW_REG_MAC_P1_MCR);