[PATCH v3 5/7] net: phy: realtek: Support SSC for the RTL8211E

[Matthias Kaehlcke <mka@chromium.org>]

By default Spread-Spectrum Clocking (SSC) is disabled on the RTL8211E.
Enable it if the device tree property 'realtek,enable-ssc' exists.

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---
TODO: DT validation

Changes in v3:
- use phydev_err() instead of dev_err()

Changes in v2:
- enable SSC in config_init() instead of probe()
- fixed error check after enabling SSC
---
 drivers/net/phy/realtek.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
index fa11ae5ebd91..5854412403b5 100644
--- a/drivers/net/phy/realtek.c
+++ b/drivers/net/phy/realtek.c
@@ -9,6 +9,7 @@
  * Copyright (c) 2004 Freescale Semiconductor, Inc.
  */
 #include <linux/bitops.h>
+#include <linux/device.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/phy.h>
@@ -33,6 +34,10 @@
 #define RTL8211E_EEE_LED_MODE1			0x05
 #define RTL8211E_EEE_LED_MODE2			0x06
 
+/* RTL8211E extension page 160 */
+#define RTL8211E_SCR				0x1a
+#define RTL8211E_SCR_DISABLE_RXC_SSC		BIT(2)
+
 #define RTL8211F_INSR				0x1d
 
 #define RTL8211F_TX_DELAY			BIT(8)
@@ -250,8 +255,18 @@ static int rtl8211f_config_init(struct phy_device *phydev)
 static int rtl8211e_config_init(struct phy_device *phydev)
 {
 	struct device *dev = &phydev->mdio.dev;
+	int ret;
 	u16 val;
 
+	if (of_property_read_bool(dev->of_node, "realtek,enable-ssc")) {
+		ret = rtl8211e_modify_ext_paged(phydev, 0xa0, RTL8211E_SCR,
+						RTL8211E_SCR_DISABLE_RXC_SSC,
+						0);
+		if (ret < 0)
+			phydev_err(phydev, "failed to enable SSC on RXC: %d\n",
+				   ret);
+	}
+
 	if (of_property_read_bool(dev->of_node, "realtek,eee-led-mode-disable"))
 		rtl8211e_disable_eee_led_mode(phydev);
 
-- 
2.22.0.410.gd8fdbe21b5-goog