regmap: Add MDIO bus support

Basic support for MDIO bus access. Support only includes clause-22
register access, with 5-bit addresses, and 16-bit wide registers.
Signed-off-by: Sander Vanheule <sander@svanheule.net>
Link: https://lore.kernel.org/r/63b99a2fec2c4ea3c461d59d451af8d675ecf312.1621279162.git.sander@svanheule.netSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/base/regmap/Kconfig

@@ -4,8 +4,9 @@
 # subsystems should select the appropriate symbols.
 
 config REGMAP
-	default y if (REGMAP_I2C || REGMAP_SPI || REGMAP_SPMI || REGMAP_W1 || REGMAP_AC97 || REGMAP_MMIO || REGMAP_IRQ || REGMAP_SOUNDWIRE || REGMAP_SOUNDWIRE_MBQ || REGMAP_SCCB || REGMAP_I3C || REGMAP_SPI_AVMM)
+	default y if (REGMAP_I2C || REGMAP_SPI || REGMAP_SPMI || REGMAP_W1 || REGMAP_AC97 || REGMAP_MMIO || REGMAP_IRQ || REGMAP_SOUNDWIRE || REGMAP_SOUNDWIRE_MBQ || REGMAP_SCCB || REGMAP_I3C || REGMAP_SPI_AVMM || REGMAP_MDIO)
 	select IRQ_DOMAIN if REGMAP_IRQ
+	select MDIO_BUS if REGMAP_MDIO
 	bool
 
 config REGCACHE_COMPRESSED
@@ -36,6 +37,9 @@ config REGMAP_W1
 	tristate
 	depends on W1
 
+config REGMAP_MDIO
+	tristate
+
 config REGMAP_MMIO
 	tristate
 

drivers/base/regmap/Makefile

@@ -19,3 +19,4 @@ obj-$(CONFIG_REGMAP_SOUNDWIRE_MBQ) += regmap-sdw-mbq.o
 obj-$(CONFIG_REGMAP_SCCB) += regmap-sccb.o
 obj-$(CONFIG_REGMAP_I3C) += regmap-i3c.o
 obj-$(CONFIG_REGMAP_SPI_AVMM) += regmap-spi-avmm.o
+obj-$(CONFIG_REGMAP_MDIO) += regmap-mdio.o

drivers/base/regmap/regmap-mdio.c

+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/errno.h>
+#include <linux/mdio.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+static int regmap_mdio_read(void *context, unsigned int reg, unsigned int *val)
+{
+	struct mdio_device *mdio_dev = context;
+	int ret;
+
+	ret = mdiobus_read(mdio_dev->bus, mdio_dev->addr, reg);
+	*val = ret & 0xffff;
+
+	return ret < 0 ? ret : 0;
+}
+
+static int regmap_mdio_write(void *context, unsigned int reg, unsigned int val)
+{
+	struct mdio_device *mdio_dev = context;
+
+	return mdiobus_write(mdio_dev->bus, mdio_dev->addr, reg, val);
+}
+
+static const struct regmap_bus regmap_mdio_bus = {
+	.reg_write = regmap_mdio_write,
+	.reg_read = regmap_mdio_read,
+};
+
+struct regmap *__regmap_init_mdio(struct mdio_device *mdio_dev,
+	const struct regmap_config *config, struct lock_class_key *lock_key,
+	const char *lock_name)
+{
+	if (config->reg_bits != 5 || config->val_bits != 16)
+		return ERR_PTR(-EOPNOTSUPP);
+
+	return __regmap_init(&mdio_dev->dev, &regmap_mdio_bus, mdio_dev, config,
+		lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__regmap_init_mdio);
+
+struct regmap *__devm_regmap_init_mdio(struct mdio_device *mdio_dev,
+	const struct regmap_config *config, struct lock_class_key *lock_key,
+	const char *lock_name)
+{
+	if (config->reg_bits != 5 || config->val_bits != 16)
+		return ERR_PTR(-EOPNOTSUPP);
+
+	return __devm_regmap_init(&mdio_dev->dev, &regmap_mdio_bus, mdio_dev,
+		config, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__devm_regmap_init_mdio);
+
+MODULE_AUTHOR("Sander Vanheule <sander@svanheule.net>");
+MODULE_DESCRIPTION("Regmap MDIO Module");
+MODULE_LICENSE("GPL v2");

include/linux/regmap.h

@@ -27,6 +27,7 @@ struct device_node;
 struct i2c_client;
 struct i3c_device;
 struct irq_domain;
+struct mdio_device;
 struct slim_device;
 struct spi_device;
 struct spmi_device;
@@ -538,6 +539,10 @@ struct regmap *__regmap_init_i2c(struct i2c_client *i2c,
 				 const struct regmap_config *config,
 				 struct lock_class_key *lock_key,
 				 const char *lock_name);
+struct regmap *__regmap_init_mdio(struct mdio_device *mdio_dev,
+				 const struct regmap_config *config,
+				 struct lock_class_key *lock_key,
+				 const char *lock_name);
 struct regmap *__regmap_init_sccb(struct i2c_client *i2c,
 				  const struct regmap_config *config,
 				  struct lock_class_key *lock_key,
@@ -594,6 +599,10 @@ struct regmap *__devm_regmap_init_i2c(struct i2c_client *i2c,
 				      const struct regmap_config *config,
 				      struct lock_class_key *lock_key,
 				      const char *lock_name);
+struct regmap *__devm_regmap_init_mdio(struct mdio_device *mdio_dev,
+				      const struct regmap_config *config,
+				      struct lock_class_key *lock_key,
+				      const char *lock_name);
 struct regmap *__devm_regmap_init_sccb(struct i2c_client *i2c,
 				       const struct regmap_config *config,
 				       struct lock_class_key *lock_key,
@@ -697,6 +706,19 @@ int regmap_attach_dev(struct device *dev, struct regmap *map,
 	__regmap_lockdep_wrapper(__regmap_init_i2c, #config,		\
 				i2c, config)
 
+/**
+ * regmap_init_mdio() - Initialise register map
+ *
+ * @mdio_dev: Device that will be interacted with
+ * @config: Configuration for register map
+ *
+ * The return value will be an ERR_PTR() on error or a valid pointer to
+ * a struct regmap.
+ */
+#define regmap_init_mdio(mdio_dev, config)				\
+	__regmap_lockdep_wrapper(__regmap_init_mdio, #config,		\
+				mdio_dev, config)
+
 /**
  * regmap_init_sccb() - Initialise register map
  *
@@ -888,6 +910,20 @@ bool regmap_ac97_default_volatile(struct device *dev, unsigned int reg);
 	__regmap_lockdep_wrapper(__devm_regmap_init_i2c, #config,	\
 				i2c, config)
 
+/**
+ * devm_regmap_init_mdio() - Initialise managed register map
+ *
+ * @mdio_dev: Device that will be interacted with
+ * @config: Configuration for register map
+ *
+ * The return value will be an ERR_PTR() on error or a valid pointer
+ * to a struct regmap.  The regmap will be automatically freed by the
+ * device management code.
+ */
+#define devm_regmap_init_mdio(mdio_dev, config)				\
+	__regmap_lockdep_wrapper(__devm_regmap_init_mdio, #config,	\
+				mdio_dev, config)
+
 /**
  * devm_regmap_init_sccb() - Initialise managed register map
  *