Re: [PATCH net-next] net: phy: broadcom: Implement suspend/resume for AC131 and BCM5241

[Florian Fainelli]

On 8/15/22 11:09, Florian Fainelli wrote:
> On 8/15/22 11:00, Russell King (Oracle) wrote:
> > On Mon, Aug 15, 2022 at 10:43:56AM -0700, Florian Fainelli wrote:
> > > +    /* We cannot use a read/modify/write here otherwise the PHY 
> > > continues
> > > +     * to drive LEDs which defeats the purpose of low power mode.
> > > +     */
> > ...
> > > +    /* Set standby mode */
> > > +    reg = phy_read(phydev, MII_BRCM_FET_SHDW_AUXMODE4);
> > > +    if (reg < 0) {
> > > +        err = reg;
> > > +        goto done;
> > > +    }
> > > +
> > > +    reg |= MII_BRCM_FET_SHDW_AM4_STANDBY;
> > > +
> > > +    err = phy_write(phydev, MII_BRCM_FET_SHDW_AUXMODE4, reg);
> >
> > Does the read-modify-write problem extend to this register? Why would
> > the PHY behave differently whether you used phy_modify() here or not?
> > On the mdio bus, it should be exactly the same - the only difference
> > is that we're guaranteed to hold the lock over the sequence whereas
> > this drops and re-acquires the lock.
>
> What read-modify-write problem are you referring to, that is, are you 
> talking about my statement about setting BMCR.PDOWN only or something else?

Sorry, hit send too quickly, I see what problem you are referring to. v2 
coming up shortly utilizing phy_modify() and simplifying the return path 
(no need for done label, etc.)

Thanks
--
Florian