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net: lan78xx: Support auto-downshift to 100Mb/s

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Ethernet cables with faulty or missing pairs (specifically pairs C and
D) allow auto-negotiation to 1000Mbs, but do not support the successful
establishment of a link. Add a DT property, "microchip,downshift-after",
to configure the number of auto-negotiation failures after which it
falls back to 100Mbs. Valid values are 2, 3, 4, 5 and 0, where 0 means
never downshift.

Signed-off-by: Phil Elwell <phil@raspberrypi.org>
This commit is contained in:
Phil Elwell
2018-11-26 19:46:58 +00:00
committed by popcornmix
parent fefe3f117b
commit 9726dcb571
3 changed files with 38 additions and 0 deletions
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3
Documentation/devicetree/bindings/net/microchip,lan78xx.txt
View File

@@ -15,6 +15,9 @@ Optional properties of the embedded PHY:
- microchip,led-modes: a 0..4 element vector, with each element configuring
the operating mode of an LED. Omitted LEDs are turned off. Allowed values
are defined in "include/dt-bindings/net/microchip-lan78xx.h".
- microchip,downshift-after: sets the number of failed auto-negotiation
attempts after which the link is downgraded from 1000BASE-T. Should be one of
2, 3, 4, 5 or 0, where 0 means never downshift.
Example:

27
drivers/net/phy/microchip.c
View File

@@ -217,6 +217,7 @@ static int lan88xx_probe(struct phy_device *phydev)
struct device *dev = &phydev->mdio.dev;
struct lan88xx_priv *priv;
u32 led_modes[4];
u32 downshift_after = 0;
int len;
priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
@@ -246,6 +247,32 @@ static int lan88xx_probe(struct phy_device *phydev)
return -EINVAL;
}
if (!of_property_read_u32(dev->of_node,
"microchip,downshift-after",
&downshift_after)) {
u32 mask = LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_MASK;
u32 val= LAN78XX_PHY_CTRL3_AUTO_DOWNSHIFT;
switch (downshift_after) {
case 2: val |= LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_2;
break;
case 3: val |= LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_3;
break;
case 4: val |= LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_4;
break;
case 5: val |= LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_5;
break;
case 0: // Disable completely
mask = LAN78XX_PHY_CTRL3_AUTO_DOWNSHIFT;
val = 0;
break;
default:
return -EINVAL;
}
(void)phy_modify_paged(phydev, 1, LAN78XX_PHY_CTRL3,
mask, val);
}
/* these values can be used to identify internal PHY */
priv->chip_id = phy_read_mmd(phydev, 3, LAN88XX_MMD3_CHIP_ID);
priv->chip_rev = phy_read_mmd(phydev, 3, LAN88XX_MMD3_CHIP_REV);

8
include/linux/microchipphy.h
View File

@@ -73,6 +73,14 @@
/* Registers specific to the LAN7800/LAN7850 embedded phy */
#define LAN78XX_PHY_LED_MODE_SELECT (0x1D)
#define LAN78XX_PHY_CTRL3 (0x14)
#define LAN78XX_PHY_CTRL3_AUTO_DOWNSHIFT (0x0010)
#define LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_MASK (0x000c)
#define LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_2 (0x0000)
#define LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_3 (0x0004)
#define LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_4 (0x0008)
#define LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_5 (0x000c)
/* DSP registers */
#define PHY_ARDENNES_MMD_DEV_3_PHY_CFG (0x806A)
#define PHY_ARDENNES_MMD_DEV_3_PHY_CFG_ZD_DLY_EN_ (0x2000)