Basic support for MIIM bus access. Support only includes clause-22
register access, with 5-bit addresses, and 16-bit wide registers.

Signed-off-by: Sander Vanheule <san...@svanheule.net>
---
 drivers/base/regmap/Kconfig       |  6 +++-
 drivers/base/regmap/Makefile      |  1 +
 drivers/base/regmap/regmap-miim.c | 58 +++++++++++++++++++++++++++++++
 include/linux/regmap.h            | 36 +++++++++++++++++++
 4 files changed, 100 insertions(+), 1 deletion(-)
 create mode 100644 drivers/base/regmap/regmap-miim.c

diff --git a/drivers/base/regmap/Kconfig b/drivers/base/regmap/Kconfig
index 50b1e2d06a25..5bcd9789284e 100644
--- a/drivers/base/regmap/Kconfig
+++ b/drivers/base/regmap/Kconfig
@@ -4,7 +4,7 @@
 # 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_MIIM)
        select IRQ_DOMAIN if REGMAP_IRQ
        bool
 
@@ -36,6 +36,10 @@ config REGMAP_W1
        tristate
        depends on W1
 
+config REGMAP_MIIM
+       tristate
+       depends on MDIO_DEVICE
+
 config REGMAP_MMIO
        tristate
 
diff --git a/drivers/base/regmap/Makefile b/drivers/base/regmap/Makefile
index 33f63adb5b3d..d80920bd42ce 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_MIIM) += regmap-miim.o
diff --git a/drivers/base/regmap/regmap-miim.c 
b/drivers/base/regmap/regmap-miim.c
new file mode 100644
index 000000000000..a560d2910417
--- /dev/null
+++ b/drivers/base/regmap/regmap-miim.c
@@ -0,0 +1,58 @@
+// 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_miim_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_miim_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_miim_bus = {
+       .reg_write = regmap_miim_write,
+       .reg_read = regmap_miim_read,
+};
+
+struct regmap *__regmap_init_miim(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(-ENOTSUPP);
+
+       return __regmap_init(&mdio_dev->dev, &regmap_miim_bus, mdio_dev, config,
+               lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__regmap_init_miim);
+
+struct regmap *__devm_regmap_init_miim(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(-ENOTSUPP);
+
+       return __devm_regmap_init(&mdio_dev->dev, &regmap_miim_bus, mdio_dev,
+               config, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__devm_regmap_init_miim);
+
+MODULE_AUTHOR("Sander Vanheule <san...@svanheule.net>");
+MODULE_DESCRIPTION("Regmap MIIM Module");
+MODULE_LICENSE("GPL v2");
+
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 2cc4ecd36298..f25630f793c3 100644
--- a/include/linux/regmap.h
+++ b/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_miim(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_miim(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_miim() - 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_miim(mdio_dev, config)                             \
+       __regmap_lockdep_wrapper(__regmap_init_miim, #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_miim() - 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_miim(mdio_dev, config)                                
\
+       __regmap_lockdep_wrapper(__devm_regmap_init_miim, #config,      \
+                               mdio_dev, config)
+
 /**
  * devm_regmap_init_sccb() - Initialise managed register map
  *
-- 
2.30.2

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