Re: [PATCH net-next 05/14] net: ethernet: mtk_eth_soc: reduce MDIO bus access latency

[Felix Fietkau]

On 2021-04-22 06:09, Ilya Lipnitskiy wrote:
> From: Felix Fietkau <nbd@xxxxxxxx>
> 
> usleep_range often ends up sleeping much longer than the 10-20us provided
> as a range here. This causes significant latency in mdio bus acceses,
> which easily adds multiple seconds to the boot time on MT7621 when polling
> DSA slave ports.
> 
> Use udelay via readx_poll_timeout_atomic, since the MDIO access does not
> take much time
> 
> Signed-off-by: Felix Fietkau <nbd@xxxxxxxx>
> [Ilya: use readx_poll_timeout_atomic instead of cond_resched]
I still prefer the cond_resched() variant. On a fully loaded system, I'd
prefer to let the MDIO access take longer instead of wasting cycles on
udelay.

- Felix