[PATCH net-next] net: phy: micrel: Add Fast link failure support for lan8842

[PATCH net-next] net: phy: micrel: Add Fast link failure support for lan8842

[Horatiu Vultur]

Add support for fast link failure for lan8842, when this is enabled the
PHY will detect link down immediately (~1ms). The disadvantage of this
is that also small instability might be reported as link down.
Therefore add this feature as a tunable configuration and the user will
know when to enable or not. By default it is not enabled.

Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
---
 drivers/net/phy/micrel.c | 77 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 75 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index e403cbbcead5b..a946c34dbbf79 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c
@@ -107,6 +107,7 @@
 #define LAN8814_INTC				0x18
 #define LAN8814_INTS				0x1B
 
+#define LAN8814_INT_FLF				BIT(15)
 #define LAN8814_INT_LINK_DOWN			BIT(2)
 #define LAN8814_INT_LINK_UP			BIT(0)
 #define LAN8814_INT_LINK			(LAN8814_INT_LINK_UP |\
@@ -2805,6 +2806,14 @@ static int ksz886x_cable_test_get_status(struct phy_device *phydev,
 	return ret;
 }
 
+/**
+ * LAN8814_PAGE_PCS - Selects Extended Page 0.
+ *
+ * This page appaers to control the fast link failure and there are different
+ * debug info registers.
+ */
+#define LAN8814_PAGE_PCS 0
+
 /**
  * LAN8814_PAGE_AFE_PMA - Selects Extended Page 1.
  *
@@ -5910,7 +5919,8 @@ static int lan8842_config_intr(struct phy_device *phydev)
 		if (err)
 			return err;
 
-		err = phy_write(phydev, LAN8814_INTC, LAN8814_INT_LINK);
+		err = phy_write(phydev, LAN8814_INTC,
+				LAN8814_INT_LINK | LAN8814_INT_FLF);
 	} else {
 		err = phy_write(phydev, LAN8814_INTC, 0);
 		if (err)
@@ -5986,7 +5996,7 @@ static irqreturn_t lan8842_handle_interrupt(struct phy_device *phydev)
 		return IRQ_NONE;
 	}
 
-	if (irq_status & LAN8814_INT_LINK) {
+	if (irq_status & (LAN8814_INT_LINK | LAN8814_INT_FLF)) {
 		phy_trigger_machine(phydev);
 		ret = IRQ_HANDLED;
 	}
@@ -6055,6 +6065,67 @@ static int lan8842_update_stats(struct phy_device *phydev)
 	return 0;
 }
 
+#define LAN8842_FLF				15 /* 0x0e */
+#define LAN8842_FLF_ENA				BIT(1)
+#define LAN8842_FLF_ENA_LINK_DOWN		BIT(0)
+
+static int lan8842_get_fast_down(struct phy_device *phydev, u8 *msecs)
+{
+	int ret;
+
+	ret = lanphy_read_page_reg(phydev, LAN8814_PAGE_PCS, LAN8842_FLF);
+	if (ret < 0)
+		return ret;
+
+	if (ret & LAN8842_FLF_ENA)
+		*msecs = ETHTOOL_PHY_FAST_LINK_DOWN_ON;
+	else
+		*msecs = ETHTOOL_PHY_FAST_LINK_DOWN_OFF;
+
+	return 0;
+}
+
+static int lan8842_set_fast_down(struct phy_device *phydev, const u8 *msecs)
+{
+	if (*msecs == ETHTOOL_PHY_FAST_LINK_DOWN_ON)
+		return lanphy_modify_page_reg(phydev, LAN8814_PAGE_PCS,
+					      LAN8842_FLF,
+					      LAN8842_FLF_ENA |
+					      LAN8842_FLF_ENA_LINK_DOWN,
+					      LAN8842_FLF_ENA |
+					      LAN8842_FLF_ENA_LINK_DOWN);
+
+	if (*msecs == ETHTOOL_PHY_FAST_LINK_DOWN_OFF)
+		return lanphy_modify_page_reg(phydev, LAN8814_PAGE_PCS,
+					      LAN8842_FLF,
+					      LAN8842_FLF_ENA |
+					      LAN8842_FLF_ENA_LINK_DOWN, 0);
+
+	return -EINVAL;
+}
+
+static int lan8842_get_tunable(struct phy_device *phydev,
+			       struct ethtool_tunable *tuna, void *data)
+{
+	switch (tuna->id) {
+	case ETHTOOL_PHY_FAST_LINK_DOWN:
+		return lan8842_get_fast_down(phydev, data);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static int lan8842_set_tunable(struct phy_device *phydev,
+			       struct ethtool_tunable *tuna, const void *data)
+{
+	switch (tuna->id) {
+	case ETHTOOL_PHY_FAST_LINK_DOWN:
+		return lan8842_set_fast_down(phydev, data);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
 static void lan8842_get_phy_stats(struct phy_device *phydev,
 				  struct ethtool_eth_phy_stats *eth_stats,
 				  struct ethtool_phy_stats *stats)
@@ -6299,6 +6370,8 @@ static struct phy_driver ksphy_driver[] = {
 	.handle_interrupt = lan8842_handle_interrupt,
 	.get_phy_stats	= lan8842_get_phy_stats,
 	.update_stats	= lan8842_update_stats,
+	.get_tunable	= lan8842_get_tunable,
+	.set_tunable	= lan8842_set_tunable,
 	.cable_test_start	= lan8814_cable_test_start,
 	.cable_test_get_status	= ksz886x_cable_test_get_status,
 }, {
-- 
2.34.1

Re: [PATCH net-next] net: phy: micrel: Add Fast link failure support for lan8842

[Russell King (Oracle)]

On Mon, Sep 15, 2025 at 11:11:49AM +0200, Horatiu Vultur wrote:
> +static int lan8842_set_fast_down(struct phy_device *phydev, const u8 *msecs)
> +{
> +	if (*msecs == ETHTOOL_PHY_FAST_LINK_DOWN_ON)
> +		return lanphy_modify_page_reg(phydev, LAN8814_PAGE_PCS,
> +					      LAN8842_FLF,
> +					      LAN8842_FLF_ENA |
> +					      LAN8842_FLF_ENA_LINK_DOWN,
> +					      LAN8842_FLF_ENA |
> +					      LAN8842_FLF_ENA_LINK_DOWN);
> +
> +	if (*msecs == ETHTOOL_PHY_FAST_LINK_DOWN_OFF)
> +		return lanphy_modify_page_reg(phydev, LAN8814_PAGE_PCS,
> +					      LAN8842_FLF,
> +					      LAN8842_FLF_ENA |
> +					      LAN8842_FLF_ENA_LINK_DOWN, 0);

Would this be more readable?

	u16 flf;

	switch (*msecs) {
	case ETHTOOL_PHY_FAST_LINK_DOWN_OFF:
		flf = 0;
		break;

	case ETHTOOL_PHY_FAST_LINK_DOWN_ON:
		flf = LAN8842_FLF_ENA | LAN8842_FLF_ENA_LINK_DOWN;
		break;

	default:
		return -EINVAL;
	}

	return lanphy_modify_page_reg(phydev, LAN8814_PAGE_PCS,
				      LAN8842_FLF,
				      LAN8842_FLF_ENA |
				      LAN8842_FLF_ENA_LINK_DOWN, flf);

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!

Re: [PATCH net-next] net: phy: micrel: Add Fast link failure support for lan8842

[Andrew Lunn]

> +/**
> + * LAN8814_PAGE_PCS - Selects Extended Page 0.
> + *
> + * This page appaers to control the fast link failure and there are different

appears.

And just curious. Why appears? Don't you have access to the data sheet?

	Andrew

Re: [PATCH net-next] net: phy: micrel: Add Fast link failure support for lan8842

[Horatiu Vultur]

The 09/15/2025 13:01, Russell King (Oracle) wrote:

Hi Russell,

> 
> On Mon, Sep 15, 2025 at 11:11:49AM +0200, Horatiu Vultur wrote:
> > +static int lan8842_set_fast_down(struct phy_device *phydev, const u8 *msecs)
> > +{
> > +     if (*msecs == ETHTOOL_PHY_FAST_LINK_DOWN_ON)
> > +             return lanphy_modify_page_reg(phydev, LAN8814_PAGE_PCS,
> > +                                           LAN8842_FLF,
> > +                                           LAN8842_FLF_ENA |
> > +                                           LAN8842_FLF_ENA_LINK_DOWN,
> > +                                           LAN8842_FLF_ENA |
> > +                                           LAN8842_FLF_ENA_LINK_DOWN);
> > +
> > +     if (*msecs == ETHTOOL_PHY_FAST_LINK_DOWN_OFF)
> > +             return lanphy_modify_page_reg(phydev, LAN8814_PAGE_PCS,
> > +                                           LAN8842_FLF,
> > +                                           LAN8842_FLF_ENA |
> > +                                           LAN8842_FLF_ENA_LINK_DOWN, 0);
> 
> Would this be more readable?
> 
>         u16 flf;
> 
>         switch (*msecs) {
>         case ETHTOOL_PHY_FAST_LINK_DOWN_OFF:
>                 flf = 0;
>                 break;
> 
>         case ETHTOOL_PHY_FAST_LINK_DOWN_ON:
>                 flf = LAN8842_FLF_ENA | LAN8842_FLF_ENA_LINK_DOWN;
>                 break;
> 
>         default:
>                 return -EINVAL;
>         }
> 
>         return lanphy_modify_page_reg(phydev, LAN8814_PAGE_PCS,
>                                       LAN8842_FLF,
>                                       LAN8842_FLF_ENA |
>                                       LAN8842_FLF_ENA_LINK_DOWN, flf);

Yes, I think it looks nicer.
I will update this in the next version.

> 
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!

-- 
/Horatiu

Re: [PATCH net-next] net: phy: micrel: Add Fast link failure support for lan8842

[Horatiu Vultur]

The 09/15/2025 14:42, Andrew Lunn wrote:

Hi Andrew,

> 
> > +/**
> > + * LAN8814_PAGE_PCS - Selects Extended Page 0.
> > + *
> > + * This page appaers to control the fast link failure and there are different
> 
> appears.

Good catch.

> 
> And just curious. Why appears? Don't you have access to the data sheet?

I have access to datasheet. It is public here:
https://www.microchip.com/en-us/product/lan8842#Documentation

The problem is that now the register are described in a different
document and this one is not yet public. I have asked and they are
working to publish also this one but I can't say if it takes a day or a
month.

And the reason why I say it 'appears' is because I have seen most of the
registers are for debug and some timers.

> 
>         Andrew

-- 
/Horatiu

Re: [PATCH net-next] net: phy: micrel: Add Fast link failure support for lan8842

[Andrew Lunn]

On Tue, Sep 16, 2025 at 09:34:27AM +0200, Horatiu Vultur wrote:
> The 09/15/2025 14:42, Andrew Lunn wrote:
> 
> Hi Andrew,
> 
> > 
> > > +/**
> > > + * LAN8814_PAGE_PCS - Selects Extended Page 0.
> > > + *
> > > + * This page appaers to control the fast link failure and there are different

> And the reason why I say it 'appears' is because I have seen most of the
> registers are for debug and some timers.

So maybe change the comment to

	This page contains timers and debug registers...

It does not matter if the document is public or not, the description
is then correct and does not give the suggestion it is guesswork.

	Andrew

Re: [PATCH net-next] net: phy: micrel: Add Fast link failure support for lan8842

[Horatiu Vultur]

The 09/16/2025 14:53, Andrew Lunn wrote:
> 
> On Tue, Sep 16, 2025 at 09:34:27AM +0200, Horatiu Vultur wrote:
> > The 09/15/2025 14:42, Andrew Lunn wrote:
> >
> > Hi Andrew,
> >
> > >
> > > > +/**
> > > > + * LAN8814_PAGE_PCS - Selects Extended Page 0.
> > > > + *
> > > > + * This page appaers to control the fast link failure and there are different
> 
> > And the reason why I say it 'appears' is because I have seen most of the
> > registers are for debug and some timers.
> 
> So maybe change the comment to
> 
>         This page contains timers and debug registers...
> 
> It does not matter if the document is public or not, the description
> is then correct and does not give the suggestion it is guesswork.

Yes, I will change this in the next version.

> 
>         Andrew

-- 
/Horatiu