[PATCH 0/3] net: phy: bcm54811: Fix the PHY initialization

[PATCH 0/3] net: phy: bcm54811: Fix the PHY initialization

[Kamil Horák (2N)]

PATCH 1 - Fix the BCM54811 PHY initialization so that it conforms
   to the datasheet regarding a reserved bit in the LRE Control
   register, which must be written to zero after every device reset.

PATCH 2 - Fix the BCM54811 PHY initialization by implementing MII-Lite
   mode switch

PATCH 3 - Add optional mii-lite-mode flag to switch the PHY to MII-Lite

Kamil Horák (2N) (3):
  net: phy: bcm54811: Fix the PHY initialization
  net: phy: bcm5481x: Implement MII-Lite mode
  dt-bindings: ethernet-phy: add optional mii-lite-mode flag

 .../devicetree/bindings/net/ethernet-phy.yaml |  8 +++
 drivers/net/phy/broadcom.c                    | 54 +++++++++++++++++--
 include/linux/brcmphy.h                       |  7 +++
 3 files changed, 66 insertions(+), 3 deletions(-)

-- 
2.39.5

[PATCH 2/3] net: phy: bcm5481x: Implement MII-Lite mode

[Kamil Horák (2N)]

The Broadcom bcm54810 and bcm54811 PHYs are capable to operate in
simplified MII mode, without TXER, RXER, CRS and COL signals as defined
for the MII. While the PHY can be strapped for MII mode, the selection
between MII and MII-Lite must be done by software.

Signed-off-by: Kamil Horák (2N) <kamilh@axis.com>
---
 drivers/net/phy/broadcom.c | 32 +++++++++++++++++++++++++++++++-
 include/linux/brcmphy.h    |  6 ++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/broadcom.c b/drivers/net/phy/broadcom.c
index 75dbb88bec5a..d0ecb12d2d2e 100644
--- a/drivers/net/phy/broadcom.c
+++ b/drivers/net/phy/broadcom.c
@@ -16,7 +16,6 @@
 #include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/phy.h>
-#include <linux/device.h>
 #include <linux/brcmphy.h>
 #include <linux/of.h>
 #include <linux/interrupt.h>
@@ -39,6 +38,7 @@ struct bcm54xx_phy_priv {
 	int	wake_irq;
 	bool	wake_irq_enabled;
 	bool	brr_mode;
+	bool	mii_lite_mode;
 };
 
 /* Link modes for BCM58411 PHY */
@@ -680,6 +680,12 @@ static int bcm5481x_read_abilities(struct phy_device *phydev)
 
 	priv->brr_mode = of_property_read_bool(np, "brr-mode");
 
+	/* Enable MII Lite (No TXER, RXER, CRS, COL) if configured */
+	err = bcm_phy_modify_exp(phydev, BCM_EXP_SYNC_ETHERNET,
+				 BCM_EXP_SYNC_ETHERNET_MII_LITE,
+				 priv->mii_lite_mode ?
+				 BCM_EXP_SYNC_ETHERNET_MII_LITE : 0);
+
 	/* Set BroadR-Reach mode as configured in the DT. */
 	err = bcm5481x_set_brrmode(phydev, priv->brr_mode);
 	if (err)
@@ -1140,6 +1146,7 @@ static int bcm54xx_phy_probe(struct phy_device *phydev)
 	struct bcm54xx_phy_priv *priv;
 	struct gpio_desc *wakeup_gpio;
 	int ret = 0;
+	struct device_node *np = phydev->mdio.dev.of_node;
 
 	priv = devm_kzalloc(&phydev->mdio.dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
@@ -1159,6 +1166,29 @@ static int bcm54xx_phy_probe(struct phy_device *phydev)
 	if (IS_ERR(priv->ptp))
 		return PTR_ERR(priv->ptp);
 
+	priv->mii_lite_mode = of_property_read_bool(np, "mii-lite-mode");
+	if (!phy_interface_is_rgmii(phydev) ||
+	    phydev->interface == PHY_INTERFACE_MODE_MII) {
+		/* Enable MII Lite (No TXER, RXER, CRS, COL) if configured */
+		ret = bcm_phy_modify_exp(phydev, BCM_EXP_SYNC_ETHERNET,
+					 BCM_EXP_SYNC_ETHERNET_MII_LITE,
+					 priv->mii_lite_mode ?
+					 BCM_EXP_SYNC_ETHERNET_MII_LITE : 0);
+		if (ret < 0)
+			return ret;
+		/* Misc Control: GMII/MII Mode (not RGMII) */
+		ret = phy_write(phydev, MII_BCM54XX_AUX_CTL,
+				MII_BCM54XX_AUXCTL_MISC_WREN |
+				MII_BCM54XX_AUXCTL_SHDWSEL_MASK |
+				MII_BCM54XX_AUXCTL_SHDWSEL_MISC |
+				(MII_BCM54XX_AUXCTL_SHDWSEL_MISC
+				  << MII_BCM54XX_AUXCTL_SHDWSEL_READ_SHIFT) |
+				MII_BCM54XX_AUXCTL_SHDWSEL_MISC_RGMII_SKEW_EN |
+				MII_BCM54XX_AUXCTL_SHDWSEL_MISC_RSVD);
+		if (ret < 0)
+			return ret;
+	}
+
 	/* We cannot utilize the _optional variant here since we want to know
 	 * whether the GPIO descriptor exists or not to advertise Wake-on-LAN
 	 * support or not.
diff --git a/include/linux/brcmphy.h b/include/linux/brcmphy.h
index 350846b010e9..115a964f3006 100644
--- a/include/linux/brcmphy.h
+++ b/include/linux/brcmphy.h
@@ -183,6 +183,12 @@
 #define BCM_LED_MULTICOLOR_ACT		0x9
 #define BCM_LED_MULTICOLOR_PROGRAM	0xa
 
+/*
+ * Broadcom Synchronous Ethernet Controls (expansion register 0x0E)
+ */
+#define BCM_EXP_SYNC_ETHERNET		(MII_BCM54XX_EXP_SEL_ER + 0x0E)
+#define BCM_EXP_SYNC_ETHERNET_MII_LITE	BIT(11)
+
 /*
  * BCM5482: Shadow registers
  * Shadow values go into bits [14:10] of register 0x1c to select a shadow
-- 
2.39.5

Re: [PATCH 2/3] net: phy: bcm5481x: Implement MII-Lite mode

[Andrew Lunn]

On Fri, Jun 20, 2025 at 03:44:28PM +0200, Kamil Horák (2N) wrote:
> The Broadcom bcm54810 and bcm54811 PHYs are capable to operate in
> simplified MII mode, without TXER, RXER, CRS and COL signals as defined
> for the MII. While the PHY can be strapped for MII mode, the selection
> between MII and MII-Lite must be done by software.

Please could you say more about what mii-lite is. Rather than adding a
bool DT property, i'm asking myself should we add interface mode for
it?

Is it a mode of its own? MII normally means Fast Ethernet, 100Mbps. Is
that what MII-Lite supports? How does it differ from RMII? Should we
be calling this PHY_INTERFACE_MODE_LMII?

	Andrew

Re: [PATCH 2/3] net: phy: bcm5481x: Implement MII-Lite mode

[Kamil Horák (2N)]

I wouldn't consider MII-Lite a separate mode (like eg. RMII), only a 
special case of MII with just those four signals not connected. As far I 
understand it, there is no need to configure the MAC for MII-Lite if the 
MAC input signals (RXER, CRS, COL) stay inactive. Because if missing COL 
(Collision), half duplex cannot be supported. The clock is limited to 25 
MHz, thus no gigabit. Besides 100Mbps, also 10Mbps, full duplex is 
supported with 2.5 MHz MII clock.
At least in the case of Broadcom PHYs, only the PHY must be explicitly 
told to switch to MII-Lite. No problem with the impossibility of half 
duplex, because all BroadR-Reach modes are full duplex only.
In turn, the RMII has less data lines (only two) and the MAC needs to be 
configured differently so it is clearly a another mode.

   Kamil

On 6/20/25 17:19, Andrew Lunn wrote:
> On Fri, Jun 20, 2025 at 03:44:28PM +0200, Kamil Horák (2N) wrote:
>> The Broadcom bcm54810 and bcm54811 PHYs are capable to operate in
>> simplified MII mode, without TXER, RXER, CRS and COL signals as defined
>> for the MII. While the PHY can be strapped for MII mode, the selection
>> between MII and MII-Lite must be done by software.
> 
> Please could you say more about what mii-lite is. Rather than adding a
> bool DT property, i'm asking myself should we add interface mode for
> it?
> 
> Is it a mode of its own? MII normally means Fast Ethernet, 100Mbps. Is
> that what MII-Lite supports? How does it differ from RMII? Should we
> be calling this PHY_INTERFACE_MODE_LMII?
> 
> 	Andrew

[PATCH 1/3] net: phy: bcm54811: Fix the PHY initialization

[Kamil Horák (2N)]

Reset the bit 12 in PHY's LRE Control register upon initialization.
According to the datasheet, this bit must be written to zero after
every device reset.

Signed-off-by: Kamil Horák (2N) <kamilh@axis.com>
---
 drivers/net/phy/broadcom.c | 22 ++++++++++++++++++++--
 include/linux/brcmphy.h    |  1 +
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/broadcom.c b/drivers/net/phy/broadcom.c
index 9b1de54fd483..75dbb88bec5a 100644
--- a/drivers/net/phy/broadcom.c
+++ b/drivers/net/phy/broadcom.c
@@ -420,11 +420,29 @@ static int bcm54811_config_init(struct phy_device *phydev)
 			return err;
 	}
 
+	err = bcm5481x_set_brrmode(phydev, priv->brr_mode);
+	if (err < 0)
+		return err;
+
 	/* With BCM54811, BroadR-Reach implies no autoneg */
-	if (priv->brr_mode)
+	if (priv->brr_mode) {
 		phydev->autoneg = 0;
+		/* Disable Long Distance Signaling, the BRR mode autoneg */
+		err = phy_modify(phydev, MII_BCM54XX_LRECR, LRECR_LDSEN, 0);
+		if (err < 0)
+			return err;
+	}
 
-	return bcm5481x_set_brrmode(phydev, priv->brr_mode);
+	if (!phy_interface_is_rgmii(phydev) ||
+	    phydev->interface == PHY_INTERFACE_MODE_MII) {
+		/* Misc Control: GMII/MII Mode (not RGMII) */
+		err = bcm54xx_auxctl_write(phydev,
+					   MII_BCM54XX_AUXCTL_SHDWSEL_MISC,
+					   MII_BCM54XX_AUXCTL_SHDWSEL_MISC_RGMII_SKEW_EN |
+					   MII_BCM54XX_AUXCTL_SHDWSEL_MISC_RSVD
+		);
+	}
+	return err;
 }
 
 static int bcm54xx_config_init(struct phy_device *phydev)
diff --git a/include/linux/brcmphy.h b/include/linux/brcmphy.h
index 028b3e00378e..350846b010e9 100644
--- a/include/linux/brcmphy.h
+++ b/include/linux/brcmphy.h
@@ -137,6 +137,7 @@
 
 #define MII_BCM54XX_AUXCTL_SHDWSEL_MISC			0x07
 #define MII_BCM54XX_AUXCTL_SHDWSEL_MISC_WIRESPEED_EN	0x0010
+#define MII_BCM54XX_AUXCTL_SHDWSEL_MISC_RSVD		0x0060
 #define MII_BCM54XX_AUXCTL_SHDWSEL_MISC_RGMII_EN	0x0080
 #define MII_BCM54XX_AUXCTL_SHDWSEL_MISC_RGMII_SKEW_EN	0x0100
 #define MII_BCM54XX_AUXCTL_MISC_FORCE_AMDIX		0x0200
-- 
2.39.5

[PATCH 3/3] dt-bindings: ethernet-phy: add optional mii-lite-mode flag

[Kamil Horák (2N)]

The Broadcom bcm54810 and bcm54811 PHYs support MII and MII-Lite
interface modes. The MII-Lite mode does not use TXR, RXER, CRS and COL
signals. However, the hardware strapping only selects MII mode,
distinction between MII and MII-Lite must be done by software.

Add optional mii-lite-mode flag to switch the PHY to MII-Lite mode.

Signed-off-by: Kamil Horák (2N) <kamilh@axis.com>
---
 Documentation/devicetree/bindings/net/ethernet-phy.yaml | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/ethernet-phy.yaml b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
index 71e2cd32580f..edfd16044770 100644
--- a/Documentation/devicetree/bindings/net/ethernet-phy.yaml
+++ b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
@@ -101,6 +101,14 @@ properties:
       1BR-10 names. The PHY must be configured to operate in BroadR-Reach mode
       by software.
 
+  mii-lite-mode:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      If set, indicates the use of MII-Lite variant of MII, without the
+      functions of TXER, RXER, CRS and COL signals for Broadcom PHYs. These
+      PHYs can be strapped to use MII mode but the MII or MII-Lite selection
+      must be done by software.
+
   clocks:
     maxItems: 1
     description:
-- 
2.39.5