[PATCH net-next v4 1/4] net: mdio: Introduce a regmap-based mdio driver

Maxime Chevallier
2023-06-01T14:15:26Z

There exists several examples today of devices that embed an ethernet
PHY or PCS directly inside an SoC. In this situation, either the device
is controlled through a vendor-specific register set, or sometimes
exposes the standard 802.3 registers that are typically accessed over
MDIO.

As phylib and phylink are designed to use mdiodevices, this driver
allows creating a virtual MDIO bus, that translates mdiodev register
accesses to regmap accesses.

The reason we use regmap is because there are at least 3 such devices
known today, 2 of them are Altera TSE PCS's, memory-mapped, exposed
with a 4-byte stride in stmmac's dwmac-socfpga variant, and a 2-byte
stride in altera-tse. The other one (nxp,sja1110-base-tx-mdio) is
exposed over SPI.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
V3->V4 :
- Clarify the KConfig description with the need for REGMAP
- Put the correct #include in the new header, as per Vlad's review
V2->V3 :
- Introduce struct mdio_regmap_priv for priv elements instead of plain
reuse of the config struct
- Use ~O instead of ~0UL
V1->V2 :
- Use phy_mask to avoid unnecessary scanning, suggested by Andrew
- Allow entirely disabling scanning, suggested by Vlad

MAINTAINERS | 7 +++
drivers/net/mdio/Kconfig | 11 ++++
drivers/net/mdio/Makefile | 1 +
drivers/net/mdio/mdio-regmap.c | 93 ++++++++++++++++++++++++++++++++
include/linux/mdio/mdio-regmap.h | 26 +++++++++
5 files changed, 138 insertions(+)
create mode 100644 drivers/net/mdio/mdio-regmap.c
create mode 100644 include/linux/mdio/mdio-regmap.h

diff --git a/MAINTAINERS b/MAINTAINERS
index c904dba1733b..f68269b39e09 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12835,6 +12835,13 @@ F: Documentation/devicetree/bindings/net/ieee802154/mcr20a.txt
F: drivers/net/ieee802154/mcr20a.c
F: drivers/net/ieee802154/mcr20a.h

+MDIO REGMAP DRIVER
+M: Maxime Chevallier <maxime.chevallier@bootlin.com>
+L: netdev@vger.kernel.org
+S: Maintained
+F: drivers/net/mdio/mdio-regmap.c
+F: include/linux/mdio/mdio-regmap.h
+
MEASUREMENT COMPUTING CIO-DAC IIO DRIVER
M: William Breathitt Gray <william.gray@linaro.org>
L: linux-iio@vger.kernel.org
diff --git a/drivers/net/mdio/Kconfig b/drivers/net/mdio/Kconfig
index 9ff2e6f22f3f..4a7a303be2f7 100644
--- a/drivers/net/mdio/Kconfig
+++ b/drivers/net/mdio/Kconfig
@@ -185,6 +185,17 @@ config MDIO_IPQ8064
This driver supports the MDIO interface found in the network
interface units of the IPQ8064 SoC

+config MDIO_REGMAP
+ tristate
+ help
+ This driver allows using MDIO devices that are not sitting on a
+ regular MDIO bus, but still exposes the standard 802.3 register
+ layout. It's regmap-based so that it can be used on integrated,
+ memory-mapped PHYs, SPI PHYs and so on. A new virtual MDIO bus is
+ created, and its read/write operations are mapped to the underlying
+ regmap. Users willing to use this driver must explicitly select
+ REGMAP.
+
config MDIO_THUNDER
tristate "ThunderX SOCs MDIO buses"
depends on 64BIT
diff --git a/drivers/net/mdio/Makefile b/drivers/net/mdio/Makefile
index 7d4cb4c11e4e..1015f0db4531 100644
--- a/drivers/net/mdio/Makefile
+++ b/drivers/net/mdio/Makefile
@@ -19,6 +19,7 @@ obj-$(CONFIG_MDIO_MOXART) += mdio-moxart.o
obj-$(CONFIG_MDIO_MSCC_MIIM) += mdio-mscc-miim.o
obj-$(CONFIG_MDIO_MVUSB) += mdio-mvusb.o
obj-$(CONFIG_MDIO_OCTEON) += mdio-octeon.o
+obj-$(CONFIG_MDIO_REGMAP) += mdio-regmap.o
obj-$(CONFIG_MDIO_SUN4I) += mdio-sun4i.o
obj-$(CONFIG_MDIO_THUNDER) += mdio-thunder.o
obj-$(CONFIG_MDIO_XGENE) += mdio-xgene.o
diff --git a/drivers/net/mdio/mdio-regmap.c b/drivers/net/mdio/mdio-regmap.c
new file mode 100644
index 000000000000..8a742a8d6387
--- /dev/null
+++ b/drivers/net/mdio/mdio-regmap.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Driver for MMIO-Mapped MDIO devices. Some IPs expose internal PHYs or PCS
+ * within the MMIO-mapped area
+ *
+ * Copyright (C) 2023 Maxime Chevallier <maxime.chevallier@bootlin.com>
+ */
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/mdio.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_mdio.h>
+#include <linux/phy.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/mdio/mdio-regmap.h>
+
+#define DRV_NAME "mdio-regmap"
+
+struct mdio_regmap_priv {
+ struct regmap *regmap;
+ u8 valid_addr;
+};
+
+static int mdio_regmap_read_c22(struct mii_bus *bus, int addr, int regnum)
+{
+ struct mdio_regmap_priv *ctx = bus->priv;
+ unsigned int val;
+ int ret;
+
+ if (ctx->valid_addr != addr)
+ return -ENODEV;
+
+ ret = regmap_read(ctx->regmap, regnum, &val);
+ if (ret < 0)
+ return ret;
+
+ return val;
+}
+
+static int mdio_regmap_write_c22(struct mii_bus *bus, int addr, int regnum,
+ u16 val)
+{
+ struct mdio_regmap_priv *ctx = bus->priv;
+
+ if (ctx->valid_addr != addr)
+ return -ENODEV;
+
+ return regmap_write(ctx->regmap, regnum, val);
+}
+
+struct mii_bus *devm_mdio_regmap_register(struct device *dev,
+ const struct mdio_regmap_config *config)
+{
+ struct mdio_regmap_priv *mr;
+ struct mii_bus *mii;
+ int rc;
+
+ if (!config->parent)
+ return ERR_PTR(-EINVAL);
+
+ mii = devm_mdiobus_alloc_size(config->parent, sizeof(*mr));
+ if (!mii)
+ return ERR_PTR(-ENOMEM);
+
+ mr = mii->priv;
+ mr->regmap = config->regmap;
+ mr->valid_addr = config->valid_addr;
+
+ mii->name = DRV_NAME;
+ strscpy(mii->id, config->name, MII_BUS_ID_SIZE);
+ mii->parent = config->parent;
+ mii->read = mdio_regmap_read_c22;
+ mii->write = mdio_regmap_write_c22;
+
+ if (config->autoscan)
+ mii->phy_mask = ~BIT(config->valid_addr);
+ else
+ mii->phy_mask = ~0;
+
+ rc = devm_mdiobus_register(dev, mii);
+ if (rc) {
+ dev_err(config->parent, "Cannot register MDIO bus![%s] (%d)\n", mii->id, rc);
+ return ERR_PTR(rc);
+ }
+
+ return mii;
+}
+EXPORT_SYMBOL_GPL(devm_mdio_regmap_register);
+
+MODULE_DESCRIPTION("MDIO API over regmap");
+MODULE_AUTHOR("Maxime Chevallier <maxime.chevallier@bootlin.com>");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/mdio/mdio-regmap.h b/include/linux/mdio/mdio-regmap.h
new file mode 100644
index 000000000000..679d9069846b
--- /dev/null
+++ b/include/linux/mdio/mdio-regmap.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Driver for MMIO-Mapped MDIO devices. Some IPs expose internal PHYs or PCS
+ * within the MMIO-mapped area
+ *
+ * Copyright (C) 2023 Maxime Chevallier <maxime.chevallier@bootlin.com>
+ */
+#ifndef MDIO_REGMAP_H
+#define MDIO_REGMAP_H
+
+#include <linux/phy.h>
+
+struct device;
+struct regmap;
+
+struct mdio_regmap_config {
+ struct device *parent;
+ struct regmap *regmap;
+ char name[MII_BUS_ID_SIZE];
+ u8 valid_addr;
+ bool autoscan;
+};
+
+struct mii_bus *devm_mdio_regmap_register(struct device *dev,
+ const struct mdio_regmap_config *config);
+
+#endif
--
2.40.1