[PATCH net-next v2 05/11] net: pcs: lynx: Convert to an MDIO driver

[Sean Anderson]

This partially converts the lynx PCS driver to a proper MDIO driver.
This allows using a more conventional driver lifecycle (e.g. with a
probe and remove). For compatibility with existing drivers, we retain
the old lynx_pcs_create/destroy functions. This may result in two
"drivers" attached to the same device (one real driver, and one attached
with lynx_pcs_create). However, this should not cause problems because
consumers will only use one or the other.

To assist in conversion of existing drivers to the PCS API, we provide a
lynx_pcs_create_on_bus function which will create an MDIO device on a
bus, bind our driver, and get the PCS. This should make it easy to
convert drivers which do not use devicetree.

Because this driver may be a direct child of its consumers (especially
when created with lynx_pcs_create_on_bus), we set suppress_bind_attrs.
This prevents userspace from causing a segfault by removing the PCS
before the consumer.

Signed-off-by: Sean Anderson <sean.anderson@xxxxxxxx>
---

Changes in v2:
- Call mdio_device_register
- Squash in lynx parts of "use pcs_get_by_provider to get PCS"
- Rewrite probe/remove functions to use create/destroy. This lets us
  convert existing drivers one at a time, instead of needing a flag day.

 drivers/net/pcs/Kconfig    | 11 +++--
 drivers/net/pcs/pcs-lynx.c | 83 +++++++++++++++++++++++++++++++++++---
 include/linux/pcs-lynx.h   |  7 +++-
 3 files changed, 91 insertions(+), 10 deletions(-)

diff --git a/drivers/net/pcs/Kconfig b/drivers/net/pcs/Kconfig
index 8d70fc52a803..5e169e87db74 100644
--- a/drivers/net/pcs/Kconfig
+++ b/drivers/net/pcs/Kconfig
@@ -25,10 +25,15 @@ config PCS_XPCS
 	  controllers.
 
 config PCS_LYNX
-	tristate
+	tristate "NXP Lynx PCS driver"
+	depends on PCS && MDIO_DEVICE
 	help
-	  This module provides helpers to phylink for managing the Lynx PCS
-	  which is part of the Layerscape and QorIQ Ethernet SERDES.
+	  This module provides driver support for the PCSs in Lynx 10g and 28g
+	  SerDes devices. These devices are present in NXP QorIQ SoCs,
+	  including the Layerscape series.
+
+	  If you want to use Ethernet on a QorIQ SoC, say "Y". If compiled as a
+	  module, it will be called "pcs-lynx".
 
 config PCS_RZN1_MIIC
 	tristate "Renesas RZ/N1 MII converter"
diff --git a/drivers/net/pcs/pcs-lynx.c b/drivers/net/pcs/pcs-lynx.c
index 7d5fc7f54b2f..3ea402049ef1 100644
--- a/drivers/net/pcs/pcs-lynx.c
+++ b/drivers/net/pcs/pcs-lynx.c
@@ -1,11 +1,14 @@
-// SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
-/* Copyright 2020 NXP
+// SPDX-License-Identifier: GPL-2.0+
+/* Copyright (C) 2022 Sean Anderson <seanga2@xxxxxxxxx>
+ * Copyright 2020 NXP
  * Lynx PCS MDIO helpers
  */
 
 #include <linux/mdio.h>
-#include <linux/phylink.h>
+#include <linux/of.h>
+#include <linux/pcs.h>
 #include <linux/pcs-lynx.h>
+#include <linux/phylink.h>
 
 #define SGMII_CLOCK_PERIOD_NS		8 /* PCS is clocked at 125 MHz */
 #define LINK_TIMER_VAL(ns)		((u32)((ns) / SGMII_CLOCK_PERIOD_NS))
@@ -333,7 +336,26 @@ struct phylink_pcs *lynx_pcs_create(struct mdio_device *mdio)
 
 	return lynx_to_phylink_pcs(lynx);
 }
-EXPORT_SYMBOL(lynx_pcs_create);
+EXPORT_SYMBOL_GPL(lynx_pcs_create);
+
+static int lynx_pcs_probe(struct mdio_device *mdio)
+{
+	struct device *dev = &mdio->dev;
+	struct phylink_pcs *pcs;
+	int ret;
+
+	pcs = lynx_pcs_create(mdio);
+	if (!pcs)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, pcs);
+	pcs->dev = dev;
+	ret = pcs_register(pcs);
+	if (ret)
+		return dev_err_probe(dev, ret, "could not register PCS\n");
+	dev_info(dev, "probed\n");
+	return 0;
+}
 
 void lynx_pcs_destroy(struct phylink_pcs *pcs)
 {
@@ -343,4 +365,55 @@ void lynx_pcs_destroy(struct phylink_pcs *pcs)
 }
 EXPORT_SYMBOL(lynx_pcs_destroy);
 
-MODULE_LICENSE("Dual BSD/GPL");
+static void lynx_pcs_remove(struct mdio_device *mdio)
+{
+	struct phylink_pcs *pcs = dev_get_drvdata(&mdio->dev);
+
+	pcs_unregister(pcs);
+	lynx_pcs_destroy(pcs);
+}
+
+static const struct of_device_id lynx_pcs_of_match[] = {
+	{ .compatible = "fsl,lynx-pcs" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, lynx_pcs_of_match);
+
+static struct mdio_driver lynx_pcs_driver = {
+	.probe = lynx_pcs_probe,
+	.remove = lynx_pcs_remove,
+	.mdiodrv.driver = {
+		.name = "lynx-pcs",
+		.of_match_table = of_match_ptr(lynx_pcs_of_match),
+		.suppress_bind_attrs = true,
+	},
+};
+mdio_module_driver(lynx_pcs_driver);
+
+struct phylink_pcs *lynx_pcs_create_on_bus(struct device *dev,
+					   struct mii_bus *bus, int addr)
+{
+	struct mdio_device *mdio;
+	struct phylink_pcs *pcs;
+	int err;
+
+	mdio = mdio_device_create(bus, addr);
+	if (IS_ERR(mdio))
+		return ERR_CAST(mdio);
+
+	mdio->bus_match = mdio_device_bus_match;
+	strncpy(mdio->modalias, "lynx-pcs", sizeof(mdio->modalias));
+	err = mdio_device_register(mdio);
+	if (err) {
+		mdio_device_free(mdio);
+		return ERR_PTR(err);
+	}
+
+	pcs = pcs_get_by_dev(dev, &mdio->dev);
+	mdio_device_free(mdio);
+	return pcs;
+}
+EXPORT_SYMBOL(lynx_pcs_create_on_bus);
+
+MODULE_DESCRIPTION("NXP Lynx 10G/28G PCS driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/pcs-lynx.h b/include/linux/pcs-lynx.h
index 5712cc2ce775..ef073b28fae9 100644
--- a/include/linux/pcs-lynx.h
+++ b/include/linux/pcs-lynx.h
@@ -6,12 +6,15 @@
 #ifndef __LINUX_PCS_LYNX_H
 #define __LINUX_PCS_LYNX_H
 
-#include <linux/mdio.h>
-#include <linux/phylink.h>
+struct device;
+struct mii_bus;
+struct phylink_pcs;
 
 struct mdio_device *lynx_get_mdio_device(struct phylink_pcs *pcs);
 
 struct phylink_pcs *lynx_pcs_create(struct mdio_device *mdio);
+struct phylink_pcs *lynx_pcs_create_on_bus(struct device *dev,
+					   struct mii_bus *bus, int addr);
 
 void lynx_pcs_destroy(struct phylink_pcs *pcs);
 
-- 
2.35.1.1320.gc452695387.dirty