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

[Wei Fang]

> -----Original Message-----
> From: Andrew Lunn <andrew@xxxxxxx>
> Sent: 2022年8月18日 9:44
> To: Wei Fang <wei.fang@xxxxxxx>
> Cc: hkallweit1@xxxxxxxxx; linux@xxxxxxxxxxxxxxx; davem@xxxxxxxxxxxxx;
> edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx;
> robh+dt@xxxxxxxxxx; krzysztof.kozlowski+dt@xxxxxxxxxx; f.fainelli@xxxxxxxxx;
> netdev@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> 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