Subject: Re: [PATCH V3 net-next 3/4] net: phy: realtek: add dt property to enable ALDPS mode

From: Jisheng Zhang <[email-masked]>
Date: Wed, 9 Jun 2021 09:56:33 +0800

On Tue, 8 Jun 2021 10:14:40 +0000
Joakim Zhang <[email-masked]> wrote:

> Hi Jisheng,

Hi,

> 
> > -----Original Message-----
> > From: Jisheng Zhang <[email-masked]>
> > Sent: 2021年6月8日 17:51
> > To: Joakim Zhang <[email-masked]>
> > Cc: [email-masked]; [email-masked]; [email-masked];
> > [email-masked]; [email-masked]; [email-masked];
> > [email-masked]; dl-linux-imx <[email-masked]>;
> > [email-masked]; [email-masked];
> > [email-masked]
> > Subject: Re: [PATCH V3 net-next 3/4] net: phy: realtek: add dt property to
> > enable ALDPS mode
> >
> > On Tue,  8 Jun 2021 11:15:34 +0800
> > Joakim Zhang <[email-masked]> wrote:
> >
> >  
> > >
> > >
> > > If enable Advance Link Down Power Saving (ALDPS) mode, it will change
> > > crystal/clock behavior, which cause RXC clock stop for dozens to
> > > hundreds of miliseconds. This is comfirmed by Realtek engineer. For
> > > some MACs, it needs RXC clock to support RX logic, after this patch,
> > > PHY can generate continuous RXC clock during auto-negotiation.
> > >
> > > ALDPS default is disabled after hardware reset, it's more reasonable
> > > to add a property to enable this feature, since ALDPS would introduce side  
> > effect.  
> > > This patch adds dt property "realtek,aldps-enable" to enable ALDPS
> > > mode per users' requirement.
> > >
> > > Jisheng Zhang enables this feature, changes the default behavior.
> > > Since mine patch breaks the rule that new implementation should not
> > > break existing design, so Cc'ed let him know to see if it can be accepted.
> > >
> > > Cc: Jisheng Zhang <[email-masked]>
> > > Signed-off-by: Joakim Zhang <[email-masked]>
> > > ---
> > >  drivers/net/phy/realtek.c | 20 +++++++++++++++++---
> > >  1 file changed, 17 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
> > > index ca258f2a9613..79dc55bb4091 100644
> > > --- a/drivers/net/phy/realtek.c
> > > +++ b/drivers/net/phy/realtek.c
> > > @@ -76,6 +76,7 @@ MODULE_AUTHOR("Johnson Leung");
> > > MODULE_LICENSE("GPL");
> > >
> > >  struct rtl821x_priv {
> > > +       u16 phycr1;
> > >         u16 phycr2;
> > >  };
> > >
> > > @@ -98,6 +99,14 @@ static int rtl821x_probe(struct phy_device *phydev)
> > >         if (!priv)
> > >                 return -ENOMEM;
> > >
> > > +       priv->phycr1 = phy_read_paged(phydev, 0xa43,  
> > RTL8211F_PHYCR1);  
> > > +       if (priv->phycr1 < 0)
> > > +               return priv->phycr1;
> > > +
> > > +       priv->phycr1 &= (RTL8211F_ALDPS_PLL_OFF |
> > > + RTL8211F_ALDPS_ENABLE | RTL8211F_ALDPS_XTAL_OFF); 

I believe your intention is

priv->phycr1 &= ~(RTL8211F_ALDPS_PLL_OFF | RTL8211F_ALDPS_ENABLE | RTL8211F_ALDPS_XTAL_OFF); 
However, this is not necessary. See below.

> >
> > priv->phycr1 is 0 by default, so above 5 LoCs can be removed  
> 
> The intention of this is to take bootloader into account. Such as uboot configure the PHY before.

The last param "set" of phy_modify_paged_changed() means *bit mask of bits to set*
If we don't want to enable ALDPS, 0 is enough.

Even if uboot configured the PHY before linux, I believe phy_modify_paged_changed()
can clear ALDPS bits w/o above 5 LoCs. 

Thanks

> 
> Best Regards,
> Joakim Zhang
> > > +       if (of_property_read_bool(dev->of_node, "realtek,aldps-enable"))
> > > +               priv->phycr1 |= RTL8211F_ALDPS_PLL_OFF |
> > > + RTL8211F_ALDPS_ENABLE | RTL8211F_ALDPS_XTAL_OFF;
> > > +
> > >         priv->phycr2 = phy_read_paged(phydev, 0xa43,  
> > RTL8211F_PHYCR2);  
> > >         if (priv->phycr2 < 0)
> > >                 return priv->phycr2;
> > > @@ -324,11 +333,16 @@ static int rtl8211f_config_init(struct phy_device  
> > *phydev)  
> > >         struct rtl821x_priv *priv = phydev->priv;
> > >         struct device *dev = &phydev->mdio.dev;
> > >         u16 val_txdly, val_rxdly;
> > > -       u16 val;
> > >         int ret;
> > >
> > > -       val = RTL8211F_ALDPS_ENABLE | RTL8211F_ALDPS_PLL_OFF |  
> > RTL8211F_ALDPS_XTAL_OFF;  
> > > -       phy_modify_paged_changed(phydev, 0xa43, RTL8211F_PHYCR1, val,  
> > val);  
> > > +       ret = phy_modify_paged_changed(phydev, 0xa43,  
> > RTL8211F_PHYCR1,  
> > > +                                      RTL8211F_ALDPS_PLL_OFF |  
> > RTL8211F_ALDPS_ENABLE | RTL8211F_ALDPS_XTAL_OFF,  
> > > +                                      priv->phycr1);
> > > +       if (ret < 0) {
> > > +               dev_err(dev, "aldps mode  configuration failed: %pe\n",
> > > +                       ERR_PTR(ret));
> > > +               return ret;
> > > +       }
> > >
> > >         switch (phydev->interface) {
> > >         case PHY_INTERFACE_MODE_RGMII:
> > > --
> > > 2.17.1
> > >  
>