[LEDE-DEV] Transmit timeouts with mtk_eth_soc and MT7621

[Mingyu Li]

Hi.

i guest the problem is there are some tx data not free. but tx
interrupt is clean. cause tx timeout. the old code will free data
first then clean interrupt. but there maybe new data arrive after free
data before clean interrupt.
so change it to clean interrupt first then clean all tx data( also
remove the budget limit). if new tx data arrive. hardware will set tx
interrupt flag. then we will free it next time.
i also apply this to rx flow.