RE: [PATCH net-next] net: phy: micrel: Adding SQI support for lan8814 phy

[<Divya.Koppera@microchip.com>]

Hi Michael,

> -----Original Message-----
> From: Michael Walle <michael@walle.cc>
> Sent: Friday, August 26, 2022 2:13 PM
> To: Divya Koppera - I30481 <Divya.Koppera@microchip.com>
> Cc: UNGLinuxDriver <UNGLinuxDriver@microchip.com>; andrew@lunn.ch;
> davem@davemloft.net; edumazet@google.com; hkallweit1@gmail.com;
> kuba@kernel.org; linux-kernel@vger.kernel.org; linux@armlinux.org.uk;
> netdev@vger.kernel.org; pabeni@redhat.com; Michael Walle
> <michael@walle.cc>
> Subject: Re: [PATCH net-next] net: phy: micrel: Adding SQI support for
> lan8814 phy
> 
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the
> content is safe
> 
> Hi,
> 
> > Supports SQI(Signal Quality Index) for lan8814 phy, where it has SQI
> > index of 0-7 values and this indicator can be used for cable integrity
> > diagnostic and investigating other noise sources.
> >
> > Signed-off-by: Divya Koppera <Divya.Koppera@microchip.com>
> > ---
> >  drivers/net/phy/micrel.c | 35 +++++++++++++++++++++++++++++++++++
> >  1 file changed, 35 insertions(+)
> >
> > diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c index
> > e78d0bf69bc3..3775da7afc64 100644
> > --- a/drivers/net/phy/micrel.c
> > +++ b/drivers/net/phy/micrel.c
> > @@ -1975,6 +1975,13 @@ static int ksz886x_cable_test_get_status(struct
> phy_device *phydev,
> >  #define LAN8814_CLOCK_MANAGEMENT                     0xd
> >  #define LAN8814_LINK_QUALITY                         0x8e
> >
> > +#define LAN8814_DCQ_CTRL                             0xe6
> > +#define LAN8814_DCQ_CTRL_READ_CAPTURE_                       BIT(15)
> 
> Why does it end with an underscore?
> 

All LAN8814 Macros that carries bit numbers are ending with _ in this driver. So following same.

> > +#define LAN8814_DCQ_CTRL_CHANNEL_MASK                        GENMASK(1,
> 0)
> > +#define LAN8814_DCQ_SQI                                      0xe4
> > +#define LAN8814_DCQ_SQI_MAX                          7
> > +#define LAN8814_DCQ_SQI_VAL_MASK                     GENMASK(3, 1)
> > +
> >  static int lanphy_read_page_reg(struct phy_device *phydev, int page,
> > u32 addr)  {
> >       int data;
> > @@ -2927,6 +2934,32 @@ static int lan8814_probe(struct phy_device
> *phydev)
> >       return 0;
> >  }
> >
> > +static int lan8814_get_sqi(struct phy_device *phydev) {
> > +     int rc, val;
> > +
> > +     val = lanphy_read_page_reg(phydev, 1, LAN8814_DCQ_CTRL);
> > +     if (val < 0)
> > +             return val;
> > +
> > +     val &= ~LAN8814_DCQ_CTRL_CHANNEL_MASK;
> 
> I do have a datasheet for this PHY, but it doesn't mention 0xe6 on EP1.

This register values are present in GPHY hard macro as below

4.2.225	DCQ Control Register
Index (In Decimal):	EP 1.230	Size:	16 bits

Can you give me the name of the datasheet which you are following, so that I'll check and let you know the reason.

> So I can only guess that this "channel mask" is for the 4 rx/tx pairs on GbE?

Yes channel mask is for wire pair.

> And you only seem to evaluate one of them. Is that the correct thing to do
> here?
> 

I found in below link is that, get_SQI returns sqi value for 100 base-t1 phy's
https://lore.kernel.org/netdev/20200519075200.24631-2-o.rempel@pengutronix.de/T/

In lan8814 phy only channel 0 is used for 100base-tx. So returning SQI value for channel 0.

> -michael
> 
> 
> > +     val |= LAN8814_DCQ_CTRL_READ_CAPTURE_;
> > +     rc = lanphy_write_page_reg(phydev, 1, LAN8814_DCQ_CTRL, val);
> > +     if (rc < 0)
> > +             return rc;
> > +
> > +     rc = lanphy_read_page_reg(phydev, 1, LAN8814_DCQ_SQI);
> > +     if (rc < 0)
> > +             return rc;
> > +
> > +     return FIELD_GET(LAN8814_DCQ_SQI_VAL_MASK, rc); }