RE: [PATCH v2 1/2] net: phy: adin: Add flags to allow disabling of fast link down

[Ken Sloat]

Hi Nuno,

> -----Original Message-----
> From: Nuno Sá <noname.nuno@xxxxxxxxx>
> Sent: Wednesday, March 1, 2023 2:34 AM
> To: Ken Sloat <ken.s@xxxxxxxxxxxxx>
> Cc: pabeni@xxxxxxxxxx; edumazet@xxxxxxxxxx; Michael Hennerich
> <michael.hennerich@xxxxxxxxxx>; David S. Miller
> <davem@xxxxxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Rob Herring
> <robh+dt@xxxxxxxxxx>; Andrew Lunn <andrew@xxxxxxx>; Heiner Kallweit
> <hkallweit1@xxxxxxxxx>; Russell King <linux@xxxxxxxxxxxxxxx>; Alexandru
> Tachici <alexandru.tachici@xxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2 1/2] net: phy: adin: Add flags to allow disabling of fast
> link down
> 
> On Tue, 2023-02-28 at 13:49 -0500, Ken Sloat wrote:
> > "Enhanced Link Detection" is an ADI PHY feature that allows for
> > earlier detection of link down if certain signal conditions are met.
> > Also known on other PHYs as "Fast Link Down," this feature is for the
> > most part enabled by default on the PHY. This is not suitable for all
> > applications and breaks the IEEE standard as explained in the ADI
> > datasheet.
> >
> > To fix this, add override flags to disable fast link down for
> > 1000BASE-T and 100BASE-TX respectively by clearing any related feature
> > enable bits.
> >
> > This new feature was tested on an ADIN1300 but according to the
> > datasheet applies equally for 100BASE-TX on the ADIN1200.
> >
> > Signed-off-by: Ken Sloat <ken.s@xxxxxxxxxxxxx>
> > ---
> > Changes in v2:
> >  -Change "FLD" nomenclature to commonly used "Fast Link Down" phrase
> > in
> >     source code and bindings. Also document this in the commit
> > comments.
> >  -Utilize phy_clear_bits_mmd() in register bit operations.
> >
> >  drivers/net/phy/adin.c | 43
> > ++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 43 insertions(+)
> >
> > diff --git a/drivers/net/phy/adin.c b/drivers/net/phy/adin.c index
> > da65215d19bb..0bab7e4d3e29 100644
> > --- a/drivers/net/phy/adin.c
> > +++ b/drivers/net/phy/adin.c
> > @@ -69,6 +69,15 @@
> >  #define ADIN1300_EEE_CAP_REG                   0x8000
> >  #define ADIN1300_EEE_ADV_REG                   0x8001
> >  #define ADIN1300_EEE_LPABLE_REG                        0x8002
> > +#define ADIN1300_FLD_EN_REG                            0x8E27 #define
> > +ADIN1300_FLD_PCS_ERR_100_EN                  BIT(7) #define
> > +ADIN1300_FLD_PCS_ERR_1000_EN                 BIT(6) #define
> > +ADIN1300_FLD_SLCR_OUT_STUCK_100_EN   BIT(5) #define
> > +ADIN1300_FLD_SLCR_OUT_STUCK_1000_EN  BIT(4) #define
> > +ADIN1300_FLD_SLCR_IN_ZDET_100_EN             BIT(3) #define
> > +ADIN1300_FLD_SLCR_IN_ZDET_1000_EN            BIT(2) #define
> > +ADIN1300_FLD_SLCR_IN_INVLD_100_EN            BIT(1) #define
> > +ADIN1300_FLD_SLCR_IN_INVLD_1000_EN   BIT(0)
> >  #define ADIN1300_CLOCK_STOP_REG                        0x9400
> >  #define ADIN1300_LPI_WAKE_ERR_CNT_REG          0xa000
> >
> > @@ -508,6 +517,36 @@ static int adin_config_clk_out(struct phy_device
> > *phydev)
> >                               ADIN1300_GE_CLK_CFG_MASK, sel);
> >  }
> >
> > +static int adin_fast_down_disable(struct phy_device *phydev) {
> > +       struct device *dev = &phydev->mdio.dev;
> > +       int rc;
> > +
> > +       if (device_property_read_bool(dev, "adi,disable-fast-down-
> > 1000base-t")) {
> > +               rc = phy_clear_bits_mmd(phydev, MDIO_MMD_VEND1,
> > +                                         ADIN1300_FLD_EN_REG,
> > +
> > ADIN1300_FLD_PCS_ERR_1000_EN |
> > +
> > ADIN1300_FLD_SLCR_OUT_STUCK_1000_EN |
> > +
> > ADIN1300_FLD_SLCR_IN_ZDET_1000_EN |
> > +
> > ADIN1300_FLD_SLCR_IN_INVLD_1000_EN);
> > +               if (rc < 0)
> > +                       return rc;
> > +       }
> > +
> > +       if (device_property_read_bool(dev, "adi,disable-fast-down-
> > 100base-tx")) {
> > +               phy_clear_bits_mmd(phydev, MDIO_MMD_VEND1,
> > +                                         ADIN1300_FLD_EN_REG,
> > +                                         ADIN1300_FLD_PCS_ERR_100_EN
> > |
> > +
> > ADIN1300_FLD_SLCR_OUT_STUCK_100_EN |
> > +
> > ADIN1300_FLD_SLCR_IN_ZDET_100_EN |
> > +
> > ADIN1300_FLD_SLCR_IN_INVLD_100_EN);
> > +               if (rc < 0)
> > +                       return rc;
> > +       }
> 
> This is not exactly what I had in mind... I was suggesting something like
> caching the complete "bits word" in both of your if() statements and then
> just calling phy_clear_bits_mmd() once. If I'm not missing something
> obvious, something like this:
> 
> u16 bits = 0; //or any other name more appropriate
> 
> if (device_property_read_bool(...))
> 	bits = ADIN1300_FLD_PCS_ERR_1000_EN | ...
> 
> if (device_property_read_bool())
> 	bits |= ...
> 
> if (!bits)
> 	return 0;
> 
> return phy_clear_bits_mmd();
> 
> Does this sound sane to you?
> 
> Anyways, this is also not a big deal...
Yes, I agree that would be cleaner. I will adjust.

> 
> - Nuno Sá

Thanks

Sincerely,
Ken Sloat