RE: [PATCH net 1/2] dt: ar803x: Document disable-hibernation property

Wei Fang
2022-08-18T02:01:15Z

> -----Original Message-----
> From: Andrew Lunn <andrew@lunn.ch>
> Sent: 2022年8月18日 9:44
> To: Wei Fang <wei.fang@nxp.com>
> Cc: hkallweit1@gmail.com; linux@armlinux.org.uk; davem@davemloft.net;
> edumazet@google.com; kuba@kernel.org; pabeni@redhat.com;
> robh+dt@kernel.org; krzysztof.kozlowski+dt@linaro.org; f.fainelli@gmail.com;
> netdev@vger.kernel.org; devicetree@vger.kernel.org;
> linux-kernel@vger.kernel.org
> Subject: Re: [PATCH net 1/2] dt: ar803x: Document disable-hibernation
> property
>
> > Yes, after the PHY enters hibernation mode that the RX_CLK stop
> > ticking, but for stmmac, it is essential that RX_CLK of PHY is present
> > for software reset completion. Otherwise, the stmmac is failed to
> > complete the software reset and can not init DMA.
>
> So the RX_CLK is more than the recovered clock from the bit stream on the
> wire. The PHY has a way to generate a clock when there is no bit stream?
>
Yes, when disable hibernation mode, the RX_CLK always output a valid clock.

> To me, it sounds like your hardware design is wrong, and it should be using the
> 25MHz reference clock. And what you are proposing is a workaround for this
> hardware problem.
>
> Anyway, i agree with Russell, a DT property is fine. But please make it clear in
> the binding documentation that disabling hibernation has the side affect of
> keeping the RX_CLK ticking when there is no link. That is probably what people
> want this for, not to actual disable hibernation.
>
> Andrew