net: phy: sfp: enable i2c-bus detection on ACPI based systems

Lookup I2C adapter using the "i2c-bus" device property on ACPI based
systems similar to how it's done with DT.

An example DSD describing an SFP on an ACPI based system:

Device (SFP0)
{
    Name (_HID, "PRP0001")
    Name (_CRS, ResourceTemplate()
    {
        GpioIo(Exclusive, PullDefault, 0, 0, IoRestrictionNone,
               "\\_SB.PCI0.RP01.GPIO", 0, ResourceConsumer)
            { 0, 1, 2, 3, 4 }
    })
    Name (_DSD, Package ()
    {
        ToUUID ("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
        Package () {
            Package () { "compatible", "sff,sfp" },
            Package () { "i2c-bus", \_SB.PCI0.RP01.I2C.MUX.CH0 },
            Package () { "maximum-power-milliwatt", 1000 },
            Package () { "tx-disable-gpios", Package () { ^SFP0, 0, 0, 1} },
            Package () { "reset-gpio",       Package () { ^SFP0, 0, 1, 1} },
            Package () { "mod-def0-gpios",   Package () { ^SFP0, 0, 2, 1} },
            Package () { "tx-fault-gpios",   Package () { ^SFP0, 0, 3, 0} },
            Package () { "los-gpios",        Package () { ^SFP0, 0, 4, 1} },
        },
    })
}

Device (PHY0)
{
    Name (_HID, "PRP0001")
    Name (_DSD, Package ()
    {
        ToUUID ("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
        Package () {
            Package () { "compatible", "ethernet-phy-ieee802.3-c45" },
            Package () { "sfp", \_SB.PCI0.RP01.SFP0 },
            Package () { "managed", "in-band-status" },
            Package () { "phy-mode", "sgmii" },
        },
    })
}
Signed-off-by: Ruslan Babayev <ruslan@babayev.com>
Cc: xe-linux-external@cisco.com
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/sfp.c

 // SPDX-License-Identifier: GPL-2.0
+#include <linux/acpi.h>
 #include <linux/ctype.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
@@ -1782,6 +1783,7 @@ static void sfp_cleanup(void *data)
 static int sfp_probe(struct platform_device *pdev)
 {
 	const struct sff_data *sff;
+	struct i2c_adapter *i2c;
 	struct sfp *sfp;
 	bool poll = false;
 	int irq, err, i;
@@ -1801,7 +1803,6 @@ static int sfp_probe(struct platform_device *pdev)
 	if (pdev->dev.of_node) {
 		struct device_node *node = pdev->dev.of_node;
 		const struct of_device_id *id;
-		struct i2c_adapter *i2c;
 		struct device_node *np;
 
 		id = of_match_node(sfp_of_match, node);
@@ -1818,6 +1819,25 @@ static int sfp_probe(struct platform_device *pdev)
 
 		i2c = of_find_i2c_adapter_by_node(np);
 		of_node_put(np);
+	} else if (has_acpi_companion(&pdev->dev)) {
+		struct acpi_device *adev = ACPI_COMPANION(&pdev->dev);
+		struct fwnode_handle *fw = acpi_fwnode_handle(adev);
+		struct fwnode_reference_args args;
+		struct acpi_handle *acpi_handle;
+		int ret;
+
+		ret = acpi_node_get_property_reference(fw, "i2c-bus", 0, &args);
+		if (ACPI_FAILURE(ret) || !is_acpi_device_node(args.fwnode)) {
+			dev_err(&pdev->dev, "missing 'i2c-bus' property\n");
+			return -ENODEV;
+		}
+
+		acpi_handle = ACPI_HANDLE_FWNODE(args.fwnode);
+		i2c = i2c_acpi_find_adapter_by_handle(acpi_handle);
+	} else {
+		return -EINVAL;
+	}
+
 	if (!i2c)
 		return -EPROBE_DEFER;
 
@@ -1826,7 +1846,6 @@ static int sfp_probe(struct platform_device *pdev)
 		i2c_put_adapter(i2c);
 		return err;
 	}
-	}
 
 	for (i = 0; i < GPIO_MAX; i++)
 		if (sff->gpios & BIT(i)) {