phy: phy-ocelot-serdes: add ability to be used in a non-syscon configuration

The phy-ocelot-serdes module has exclusively been used in a syscon setup,
from an internal CPU. The addition of external control of ocelot switches
via an existing MFD implementation means that syscon is no longer the only
interface that phy-ocelot-serdes will see.

In the MFD configuration, an IORESOURCE_REG resource will exist for the
device. Utilize this resource to be able to function in both syscon and
non-syscon configurations.
Signed-off-by: Colin Foster <colin.foster@in-advantage.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/phy/mscc/phy-ocelot-serdes.c

@@ -494,6 +494,7 @@ static int serdes_probe(struct platform_device *pdev)
 {
 	struct phy_provider *provider;
 	struct serdes_ctrl *ctrl;
+	struct resource *res;
 	unsigned int i;
 	int ret;
 
@@ -503,6 +504,14 @@ static int serdes_probe(struct platform_device *pdev)
 
 	ctrl->dev = &pdev->dev;
 	ctrl->regs = syscon_node_to_regmap(pdev->dev.parent->of_node);
+	if (IS_ERR(ctrl->regs)) {
+		/* Fall back to using IORESOURCE_REG, if possible */
+		res = platform_get_resource(pdev, IORESOURCE_REG, 0);
+		if (res)
+			ctrl->regs = dev_get_regmap(ctrl->dev->parent,
+						    res->name);
+	}
+
 	if (IS_ERR(ctrl->regs))
 		return PTR_ERR(ctrl->regs);