linux-kernel - Re: [PATCH net-next 2/2] net: phy: micrel: lan8814 cable improvement errata

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Date: Wed, 28 Feb 2024 15:02:06 +0100
From: Horatiu Vultur <horatiu.vultur@...rochip.com>
To: Wojciech Drewek <wojciech.drewek@...el.com>
CC: <andrew@...n.ch>, <hkallweit1@...il.com>, <linux@...linux.org.uk>,
	<davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <UNGLinuxDriver@...rochip.com>
Subject: Re: [PATCH net-next 2/2] net: phy: micrel: lan8814 cable improvement
 errata

The 02/28/2024 11:03, Wojciech Drewek wrote:

Hi Wojciech,

> 
> On 28.02.2024 07:28, Horatiu Vultur wrote:
> > When the length of the cable is more than 100m and the lan8814 is
> > configured to run in 1000Base-T Slave then the register of the device
> > needs to be optimized.
> >
> > Workaround this by setting the measure time to a value of 0xb. This
> > value can be set regardless of the configuration.
> >
> > This issue is described in 'LAN8814 Silicon Errata and Data Sheet
> > Clarification' and according to that, this will not be corrected in a
> > future silicon revision.
> >
> > Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com>
> > ---
> >  drivers/net/phy/micrel.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
> > index 5a0cc89eaebdd..1e3b0436e161e 100644
> > --- a/drivers/net/phy/micrel.c
> > +++ b/drivers/net/phy/micrel.c
> > @@ -117,6 +117,10 @@
> >  #define LAN8814_EEE_STATE                    0x38
> >  #define LAN8814_EEE_STATE_MASK2P5P           BIT(10)
> >
> > +#define LAN8814_PD_CONTROLS                  0x9d
> > +#define LAN8814_PD_CONTROLS_PD_MEAS_TIME_MASK_       GENMASK(3, 0)
> > +#define LAN8814_PD_CONTROLS_PD_MEAS_TIME_VAL_        0xb
> > +
> >  /* Represents 1ppm adjustment in 2^32 format with
> >   * each nsec contains 4 clock cycles.
> >   * The value is calculated as following: (1/1000000)/((2^-32)/4)
> > @@ -3302,6 +3306,12 @@ static void lan8814_errata_fixes(struct phy_device *phydev)
> >       val = lanphy_read_page_reg(phydev, 2, LAN8814_EEE_STATE);
> >       val &= ~LAN8814_EEE_STATE_MASK2P5P;
> >       lanphy_write_page_reg(phydev, 2, LAN8814_EEE_STATE, val);
> > +
> > +     /* Improve cable reach beyond 100m */
> > +     val = lanphy_read_page_reg(phydev, 1, LAN8814_PD_CONTROLS);
> > +     val &= ~LAN8814_PD_CONTROLS_PD_MEAS_TIME_MASK_;
> > +     val |= LAN8814_PD_CONTROLS_PD_MEAS_TIME_VAL_;
> > +     lanphy_write_page_reg(phydev, 1, LAN8814_PD_CONTROLS, val);
> 
> Ok, now I see that the second fix is also in lan8814_errata_fixes.
> I'd suggest to split both fixes to separate functions and name them
> in more descriptive way.

Yes, I can do that. Then I will create a separate function for each
errata fix and I will do the same also for future erratas.

> 
> >  }
> >
> >  static int lan8814_probe(struct phy_device *phydev)

-- 
/Horatiu