[PATCH] net: phy: micrel: workaround for errata #2 for KSZ9031

[Marco Felsch]

From: Markus Niebel <markus.nie...@tqs.de>

handle errata #2 for KSZ9031: force 1000Base-T master

Attention: enabling the workaround will cause no link to
other GIGE master.

Signed-off-by: Markus Niebel <markus.nie...@tqs.de>
[m.fel...@pengutronix.de: move dt binding to the KSZ9031 entry]
Signed-off-by: Marco Felsch <m.fel...@pengutronix.de>
---
 .../devicetree/bindings/net/micrel-ksz90x1.txt |  3 +++
 drivers/net/phy/micrel.c                       | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt 
b/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt
index 42a248301615..e2465fbbbcef 100644
--- a/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt
+++ b/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt
@@ -57,6 +57,9 @@ KSZ9031:
       - txd2-skew-ps : Skew control of TX data 2 pad
       - txd3-skew-ps : Skew control of TX data 3 pad
 
+    - force-master: Boolean, force phy to master mode. This is a
+                    workaround at least for KSZ9031 errata #2.
+
 Examples:
 
        mdio {
diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index f41b224a9cdb..3e4243e4f7a7 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c
@@ -528,6 +528,8 @@ static int ksz9031_enable_edpd(struct phy_device *phydev)
 
 static int ksz9031_config_init(struct phy_device *phydev)
 {
+       int rc;
+       u16 val;
        const struct device *dev = &phydev->mdio.dev;
        const struct device_node *of_node = dev->of_node;
        static const char *clk_skews[2] = {"rxc-skew-ps", "txc-skew-ps"};
@@ -573,6 +575,22 @@ static int ksz9031_config_init(struct phy_device *phydev)
                ksz9031_of_load_skew_values(phydev, of_node,
                                MII_KSZ9031RN_TX_DATA_PAD_SKEW, 4,
                                tx_data_skews, 4);
+
+               /* force master mode -> errata #2
+                * attention: Master <-> Master will not work
+                */
+               if (of_property_read_bool(of_node, "force-master")) {
+                       rc = phy_read(phydev, MII_CTRL1000);
+                       if (rc >= 0) {
+                               val = (u16)rc;
+                               /* enable master mode, config &
+                                * prefer master
+                                */
+                               val |= (CTL1000_ENABLE_MASTER |
+                                       CTL1000_AS_MASTER);
+                               phy_write(phydev, MII_CTRL1000, val);
+                       }
+               }
        }
 
        return ksz9031_center_flp_timing(phydev);
-- 
2.17.0