drivers: net: xgene: Poll link status via GPIO

When 10GbE SFP+ module is not plugged in or cable is not connected,
the link status register does not report the proper state due
to floating signal. This patch checks the module present status via an
GPIO to determine whether to ignore the link status register and report
link down.
Signed-off-by: Quan Nguyen <qnguyen@apm.com>
Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Tested-by: Fushen Chen <fchen@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/apm/xgene/Kconfig

@@ -4,6 +4,7 @@ config NET_XGENE
 	depends on ARCH_XGENE || COMPILE_TEST
 	select PHYLIB
 	select MDIO_XGENE
+	select GPIOLIB
 	help
 	  This is the Ethernet driver for the on-chip ethernet interface on the
 	  APM X-Gene SoC.

drivers/net/ethernet/apm/xgene/xgene_enet_main.c

@@ -19,6 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/gpio.h>
 #include "xgene_enet_main.h"
 #include "xgene_enet_hw.h"
 #include "xgene_enet_sgmac.h"
@@ -1320,6 +1321,18 @@ static int xgene_enet_check_phy_handle(struct xgene_enet_pdata *pdata)
 	return 0;
 }
 
+static void xgene_enet_gpiod_get(struct xgene_enet_pdata *pdata)
+{
+	struct device *dev = &pdata->pdev->dev;
+
+	if (pdata->phy_mode != PHY_INTERFACE_MODE_XGMII)
+		return;
+
+	pdata->sfp_rdy = gpiod_get(dev, "rxlos", GPIOD_IN);
+	if (IS_ERR(pdata->sfp_rdy))
+		pdata->sfp_rdy = gpiod_get(dev, "sfp", GPIOD_IN);
+}
+
 static int xgene_enet_get_resources(struct xgene_enet_pdata *pdata)
 {
 	struct platform_device *pdev;
@@ -1409,6 +1422,8 @@ static int xgene_enet_get_resources(struct xgene_enet_pdata *pdata)
 	if (ret)
 		return ret;
 
+	xgene_enet_gpiod_get(pdata);
+
 	pdata->clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(pdata->clk)) {
 		/* Firmware may have set up the clock already. */

drivers/net/ethernet/apm/xgene/xgene_enet_main.h

@@ -217,6 +217,7 @@ struct xgene_enet_pdata {
 	u8 tx_delay;
 	u8 rx_delay;
 	bool mdio_driver;
+	struct gpio_desc *sfp_rdy;
 };
 
 struct xgene_indirect_ctl {

drivers/net/ethernet/apm/xgene/xgene_enet_xgmac.c

@@ -18,6 +18,8 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/of_gpio.h>
+#include <linux/gpio.h>
 #include "xgene_enet_main.h"
 #include "xgene_enet_hw.h"
 #include "xgene_enet_xgmac.h"
@@ -399,10 +401,14 @@ static void xgene_enet_link_state(struct work_struct *work)
 {
 	struct xgene_enet_pdata *pdata = container_of(to_delayed_work(work),
 					 struct xgene_enet_pdata, link_work);
+	struct gpio_desc *sfp_rdy = pdata->sfp_rdy;
 	struct net_device *ndev = pdata->ndev;
 	u32 link_status, poll_interval;
 
 	link_status = xgene_enet_link_status(pdata);
+	if (link_status && !IS_ERR(sfp_rdy) && !gpiod_get_value(sfp_rdy))
+		link_status = 0;
+
 	if (link_status) {
 		if (!netif_carrier_ok(ndev)) {
 			netif_carrier_on(ndev);