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.net
Signed-off-by: Mark Brown <broonie@kernel.org>

3 files changed, 63 insertions, 1 deletions

diff --git a/drivers/base/regmap/Kconfig b/drivers/base/regmap/Kconfig
index 50b1e2d06a25..159bac6c5046 100644
--- a/drivers/base/regmap/Kconfig
+++ b/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
 
diff --git a/drivers/base/regmap/Makefile b/drivers/base/regmap/Makefile
index 33f63adb5b3d..11facb32a027 100644
--- a/drivers/base/regmap/Makefile
+++ b/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
diff --git a/drivers/base/regmap/regmap-mdio.c b/drivers/base/regmap/regmap-mdio.c
new file mode 100644
index 000000000000..5f18fe409f56
--- /dev/null
+++ b/drivers/base/regmap/regmap-mdio.c
@@ -0,0 +1,57 @@
+// 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");