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

[Ilya Lipnitskiy]

On Thu, Apr 22, 2021 at 5:33 AM Felix Fietkau <nbd at nbd.name> wrote:
>
>
> On 2021-04-22 06:09, Ilya Lipnitskiy wrote:
> > From: Felix Fietkau <nbd at nbd.name>
> >
> > 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 at nbd.name>
> > [Ilya: use readx_poll_timeout_atomic instead of cond_resched]
> I still prefer the cond_resched() variant.
No problem, I will respin with your original change. Looks like we
can't take advantage of iopoll.h routine in this case, but that's not
the end of the world!

> On a fully loaded system, I'd
> prefer to let the MDIO access take longer instead of wasting cycles on
> udelay.
>
> - Felix

Ilya