[net-next PATCH] drivers: net: cpsw: Add support to make gpio drive which slave connected to phy

[Mugunthan V N <mugunthanvnm@ti.com>]

In DRA72x EVM, by default slave 1 is connected to the onboard
phy, but slave 2 pins are also muxed with video input module
which is controlled by pcf857x gpio and currently to select slave
0 to connect to phy gpio hogging is used, but with
omap2plus_defconfig the pcf857x gpio is built as module. So when
using NFS on DRA72x EVM, board doesn't boot as gpio hogging do
not set proper gpio state to connect slave 0 to phy as it is
built as module and you do not see any errors for not setting
gpio and just mentions dhcp reply not got.

To solve this issue, introducing "select-slave-gpio" in DT when
gpio based muxing is required. This will through a warning when
vgpio get fails and returns probe defer. When gpio-pcf857x module
is installed, cpsw probes again and ethernet becomes functional.
Verified this on DRA72x with pcf as module and ramdisk [1]

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
---

This patch is texted on DRA72x, Logs [1] and pushed a branch [2]

[1]: http://pastebin.ubuntu.com/12244652/
[2]: git://git.ti.com/~mugunthanvnm/ti-linux-kernel/linux.git cpsw-gpio-optional

---
 Documentation/devicetree/bindings/net/cpsw.txt |  3 +++
 drivers/net/ethernet/ti/cpsw.c                 | 10 ++++++++++
 2 files changed, 13 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/cpsw.txt b/Documentation/devicetree/bindings/net/cpsw.txt
index 33fe846..cb693aa 100644
--- a/Documentation/devicetree/bindings/net/cpsw.txt
+++ b/Documentation/devicetree/bindings/net/cpsw.txt
@@ -26,6 +26,9 @@ Optional properties:
 - dual_emac		: Specifies Switch to act as Dual EMAC
 - syscon		: Phandle to the system control device node, which is
 			  the control module device of the am33x
+- select-slave-gpio	: Should be added if a gpio line is required to
+			  select which slave is connected to phy
+
 
 Slave Properties:
 Required properties:
diff --git a/drivers/net/ethernet/ti/cpsw.c b/drivers/net/ethernet/ti/cpsw.c
index 8fc90f1..ce965ad 100644
--- a/drivers/net/ethernet/ti/cpsw.c
+++ b/drivers/net/ethernet/ti/cpsw.c
@@ -29,6 +29,7 @@
 #include <linux/workqueue.h>
 #include <linux/delay.h>
 #include <linux/pm_runtime.h>
+#include <linux/gpio.h>
 #include <linux/of.h>
 #include <linux/of_net.h>
 #include <linux/of_device.h>
@@ -2207,6 +2208,7 @@ static int cpsw_probe(struct platform_device *pdev)
 	void __iomem			*ss_regs;
 	struct resource			*res, *ss_res;
 	const struct of_device_id	*of_id;
+	struct gpio_desc		*select_slave;
 	u32 slave_offset, sliver_offset, slave_size;
 	int ret = 0, i;
 	int irq;
@@ -2232,6 +2234,14 @@ static int cpsw_probe(struct platform_device *pdev)
 		goto clean_ndev_ret;
 	}
 
+	select_slave = devm_gpiod_get_optional(&pdev->dev, "select-slave",
+					       GPIOD_OUT_LOW);
+	if (IS_ERR(select_slave)) {
+		ret = PTR_ERR(select_slave);
+		dev_err(&pdev->dev, "gpio request failed, ret %d\n", ret);
+		goto clean_ndev_ret;
+	}
+
 	/*
 	 * This may be required here for child devices.
 	 */
-- 
2.5.0.474.g3a9835b