diff mbox series

[2/4] net: phy: Add mdio-aspeed

Message ID 20190729043926.32679-3-andrew@aj.id.au (mailing list archive)
State New, archived
Headers show
Series net: phy: Add AST2600 MDIO support | expand

Commit Message

Andrew Jeffery July 29, 2019, 4:39 a.m. UTC 
The AST2600 design separates the MDIO controllers from the MAC, which is
where they were placed in the AST2400 and AST2500. Further, the register
interface is reworked again, so now we have three possible different
interface implementations, however this driver only supports the
interface provided by the AST2600. The AST2400 and AST2500 will continue
to be supported by the MDIO support embedded in the FTGMAC100 driver.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
---
 drivers/net/phy/Kconfig       |  13 +++
 drivers/net/phy/Makefile      |   1 +
 drivers/net/phy/mdio-aspeed.c | 159 ++++++++++++++++++++++++++++++++++
 3 files changed, 173 insertions(+)
 create mode 100644 drivers/net/phy/mdio-aspeed.c

Comments

Andrew Lunn July 29, 2019, 1:32 p.m. UTC | #1 
On Mon, Jul 29, 2019 at 02:09:24PM +0930, Andrew Jeffery wrote:
> The AST2600 design separates the MDIO controllers from the MAC, which is
> where they were placed in the AST2400 and AST2500. Further, the register
> interface is reworked again, so now we have three possible different
> interface implementations, however this driver only supports the
> interface provided by the AST2600. The AST2400 and AST2500 will continue
> to be supported by the MDIO support embedded in the FTGMAC100 driver.
> 
> Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
> ---
>  drivers/net/phy/Kconfig       |  13 +++
>  drivers/net/phy/Makefile      |   1 +
>  drivers/net/phy/mdio-aspeed.c | 159 ++++++++++++++++++++++++++++++++++
>  3 files changed, 173 insertions(+)
>  create mode 100644 drivers/net/phy/mdio-aspeed.c
> 
> diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
> index 20f14c5fbb7e..206d8650ee7f 100644
> --- a/drivers/net/phy/Kconfig
> +++ b/drivers/net/phy/Kconfig
> @@ -21,6 +21,19 @@ config MDIO_BUS
>  
>  if MDIO_BUS
>  
> +config MDIO_ASPEED
> +	tristate "ASPEED MDIO bus controller"
> +	depends on ARCH_ASPEED || COMPILE_TEST
> +	depends on OF_MDIO && HAS_IOMEM
> +	help
> +	  This module provides a driver for the independent MDIO bus
> +	  controllers found in the ASPEED AST2600 SoC. This is a driver for the
> +	  third revision of the ASPEED MDIO register interface - the first two
> +	  revisions are the "old" and "new" interfaces found in the AST2400 and
> +	  AST2500, embedded in the MAC. For legacy reasons, FTGMAC100 driver
> +	  continues to drive the embedded MDIO controller for the AST2400 and
> +	  AST2500 SoCs, so say N if AST2600 support is not required.
> +
>  config MDIO_BCM_IPROC
>  	tristate "Broadcom iProc MDIO bus controller"
>  	depends on ARCH_BCM_IPROC || COMPILE_TEST
> diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
> index 839acb292c38..ba07c27e4208 100644
> --- a/drivers/net/phy/Makefile
> +++ b/drivers/net/phy/Makefile
> @@ -22,6 +22,7 @@ libphy-$(CONFIG_LED_TRIGGER_PHY)	+= phy_led_triggers.o
>  obj-$(CONFIG_PHYLINK)		+= phylink.o
>  obj-$(CONFIG_PHYLIB)		+= libphy.o
>  
> +obj-$(CONFIG_MDIO_ASPEED)	+= mdio-aspeed.o
>  obj-$(CONFIG_MDIO_BCM_IPROC)	+= mdio-bcm-iproc.o
>  obj-$(CONFIG_MDIO_BCM_UNIMAC)	+= mdio-bcm-unimac.o
>  obj-$(CONFIG_MDIO_BITBANG)	+= mdio-bitbang.o
> diff --git a/drivers/net/phy/mdio-aspeed.c b/drivers/net/phy/mdio-aspeed.c
> new file mode 100644
> index 000000000000..71496a9ff54a
> --- /dev/null
> +++ b/drivers/net/phy/mdio-aspeed.c
> @@ -0,0 +1,159 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/* Copyright (C) 2019 IBM Corp. */
> +
> +#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>
> +
> +#define DRV_NAME "mdio-aspeed"
> +
> +#define ASPEED_MDIO_CTRL		0x0
> +#define   ASPEED_MDIO_CTRL_FIRE		BIT(31)
> +#define   ASPEED_MDIO_CTRL_ST		BIT(28)
> +#define     ASPEED_MDIO_CTRL_ST_C45	0
> +#define     ASPEED_MDIO_CTRL_ST_C22	1
> +#define   ASPEED_MDIO_CTRL_OP		GENMASK(27, 26)
> +#define     MDIO_C22_OP_WRITE		0b01
> +#define     MDIO_C22_OP_READ		0b10
> +#define   ASPEED_MDIO_CTRL_PHYAD	GENMASK(25, 21)
> +#define   ASPEED_MDIO_CTRL_REGAD	GENMASK(20, 16)
> +#define   ASPEED_MDIO_CTRL_MIIWDATA	GENMASK(15, 0)
> +
> +#define ASPEED_MDIO_DATA		0x4
> +#define   ASPEED_MDIO_DATA_MDC_THRES	GENMASK(31, 24)
> +#define   ASPEED_MDIO_DATA_MDIO_EDGE	BIT(23)
> +#define   ASPEED_MDIO_DATA_MDIO_LATCH	GENMASK(22, 20)
> +#define   ASPEED_MDIO_DATA_IDLE		BIT(16)
> +#define   ASPEED_MDIO_DATA_MIIRDATA	GENMASK(15, 0)
> +
> +#define ASPEED_MDIO_RETRIES		10
> +
> +struct aspeed_mdio {
> +	void __iomem *base;
> +};
> +
> +static int aspeed_mdio_read(struct mii_bus *bus, int addr, int regnum)
> +{
> +	struct aspeed_mdio *ctx = bus->priv;
> +	u32 ctrl;
> +	int i;
> +
> +	dev_dbg(&bus->dev, "%s: addr: %d, regnum: %d\n", __func__, addr,
> +		regnum);
> +
> +	/* Just clause 22 for the moment */
> +	ctrl = ASPEED_MDIO_CTRL_FIRE

Hi Andrew

In the binding, you say C45 is supported. Here you don't. It would be
nice to be consistent.


> +		| FIELD_PREP(ASPEED_MDIO_CTRL_ST, ASPEED_MDIO_CTRL_ST_C22)
> +		| FIELD_PREP(ASPEED_MDIO_CTRL_OP, MDIO_C22_OP_READ)
> +		| FIELD_PREP(ASPEED_MDIO_CTRL_PHYAD, addr)
> +		| FIELD_PREP(ASPEED_MDIO_CTRL_REGAD, regnum);
> +
> +	iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL);
> +
> +	for (i = 0; i < ASPEED_MDIO_RETRIES; i++) {
> +		u32 data;
> +
> +		data = ioread32(ctx->base + ASPEED_MDIO_DATA);
> +		if (data & ASPEED_MDIO_DATA_IDLE)
> +			return FIELD_GET(ASPEED_MDIO_DATA_MIIRDATA, data);
> +
> +		udelay(100);
> +	}

One of the readx_poll_timeout functions could be used.

> +
> +	dev_err(&bus->dev, "MDIO read failed\n");
> +	return -EIO;
> +}
> +
> +static int aspeed_mdio_write(struct mii_bus *bus, int addr, int regnum, u16 val)
> +{
> +	struct aspeed_mdio *ctx = bus->priv;
> +	u32 ctrl;
> +	int i;
> +
> +	dev_dbg(&bus->dev, "%s: addr: %d, regnum: %d, val: 0x%x\n",
> +		__func__, addr, regnum, val);
> +
> +	/* Just clause 22 for the moment */
> +	ctrl = ASPEED_MDIO_CTRL_FIRE
> +		| FIELD_PREP(ASPEED_MDIO_CTRL_ST, ASPEED_MDIO_CTRL_ST_C22)
> +		| FIELD_PREP(ASPEED_MDIO_CTRL_OP, MDIO_C22_OP_WRITE)
> +		| FIELD_PREP(ASPEED_MDIO_CTRL_PHYAD, addr)
> +		| FIELD_PREP(ASPEED_MDIO_CTRL_REGAD, regnum)
> +		| FIELD_PREP(ASPEED_MDIO_CTRL_MIIWDATA, val);
> +
> +	iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL);
> +
> +	for (i = 0; i < ASPEED_MDIO_RETRIES; i++) {
> +		ctrl = ioread32(ctx->base + ASPEED_MDIO_CTRL);
> +		if (!(ctrl & ASPEED_MDIO_CTRL_FIRE))
> +			return 0;
> +
> +		udelay(100);
> +	}

readx_poll_timeout() here as well.

Otherwise this looks good.

	  Andrew
Andrew Jeffery July 30, 2019, 2:23 a.m. UTC | #2 
On Mon, 29 Jul 2019, at 23:03, Andrew Lunn wrote:
> On Mon, Jul 29, 2019 at 02:09:24PM +0930, Andrew Jeffery wrote:
> > The AST2600 design separates the MDIO controllers from the MAC, which is
> > where they were placed in the AST2400 and AST2500. Further, the register
> > interface is reworked again, so now we have three possible different
> > interface implementations, however this driver only supports the
> > interface provided by the AST2600. The AST2400 and AST2500 will continue
> > to be supported by the MDIO support embedded in the FTGMAC100 driver.
> > 
> > Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
> > ---
> >  drivers/net/phy/Kconfig       |  13 +++
> >  drivers/net/phy/Makefile      |   1 +
> >  drivers/net/phy/mdio-aspeed.c | 159 ++++++++++++++++++++++++++++++++++
> >  3 files changed, 173 insertions(+)
> >  create mode 100644 drivers/net/phy/mdio-aspeed.c
> > 
> > diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
> > index 20f14c5fbb7e..206d8650ee7f 100644
> > --- a/drivers/net/phy/Kconfig
> > +++ b/drivers/net/phy/Kconfig
> > @@ -21,6 +21,19 @@ config MDIO_BUS
> >  
> >  if MDIO_BUS
> >  
> > +config MDIO_ASPEED
> > +	tristate "ASPEED MDIO bus controller"
> > +	depends on ARCH_ASPEED || COMPILE_TEST
> > +	depends on OF_MDIO && HAS_IOMEM
> > +	help
> > +	  This module provides a driver for the independent MDIO bus
> > +	  controllers found in the ASPEED AST2600 SoC. This is a driver for the
> > +	  third revision of the ASPEED MDIO register interface - the first two
> > +	  revisions are the "old" and "new" interfaces found in the AST2400 and
> > +	  AST2500, embedded in the MAC. For legacy reasons, FTGMAC100 driver
> > +	  continues to drive the embedded MDIO controller for the AST2400 and
> > +	  AST2500 SoCs, so say N if AST2600 support is not required.
> > +
> >  config MDIO_BCM_IPROC
> >  	tristate "Broadcom iProc MDIO bus controller"
> >  	depends on ARCH_BCM_IPROC || COMPILE_TEST
> > diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
> > index 839acb292c38..ba07c27e4208 100644
> > --- a/drivers/net/phy/Makefile
> > +++ b/drivers/net/phy/Makefile
> > @@ -22,6 +22,7 @@ libphy-$(CONFIG_LED_TRIGGER_PHY)	+= phy_led_triggers.o
> >  obj-$(CONFIG_PHYLINK)		+= phylink.o
> >  obj-$(CONFIG_PHYLIB)		+= libphy.o
> >  
> > +obj-$(CONFIG_MDIO_ASPEED)	+= mdio-aspeed.o
> >  obj-$(CONFIG_MDIO_BCM_IPROC)	+= mdio-bcm-iproc.o
> >  obj-$(CONFIG_MDIO_BCM_UNIMAC)	+= mdio-bcm-unimac.o
> >  obj-$(CONFIG_MDIO_BITBANG)	+= mdio-bitbang.o
> > diff --git a/drivers/net/phy/mdio-aspeed.c b/drivers/net/phy/mdio-aspeed.c
> > new file mode 100644
> > index 000000000000..71496a9ff54a
> > --- /dev/null
> > +++ b/drivers/net/phy/mdio-aspeed.c
> > @@ -0,0 +1,159 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/* Copyright (C) 2019 IBM Corp. */
> > +
> > +#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>
> > +
> > +#define DRV_NAME "mdio-aspeed"
> > +
> > +#define ASPEED_MDIO_CTRL		0x0
> > +#define   ASPEED_MDIO_CTRL_FIRE		BIT(31)
> > +#define   ASPEED_MDIO_CTRL_ST		BIT(28)
> > +#define     ASPEED_MDIO_CTRL_ST_C45	0
> > +#define     ASPEED_MDIO_CTRL_ST_C22	1
> > +#define   ASPEED_MDIO_CTRL_OP		GENMASK(27, 26)
> > +#define     MDIO_C22_OP_WRITE		0b01
> > +#define     MDIO_C22_OP_READ		0b10
> > +#define   ASPEED_MDIO_CTRL_PHYAD	GENMASK(25, 21)
> > +#define   ASPEED_MDIO_CTRL_REGAD	GENMASK(20, 16)
> > +#define   ASPEED_MDIO_CTRL_MIIWDATA	GENMASK(15, 0)
> > +
> > +#define ASPEED_MDIO_DATA		0x4
> > +#define   ASPEED_MDIO_DATA_MDC_THRES	GENMASK(31, 24)
> > +#define   ASPEED_MDIO_DATA_MDIO_EDGE	BIT(23)
> > +#define   ASPEED_MDIO_DATA_MDIO_LATCH	GENMASK(22, 20)
> > +#define   ASPEED_MDIO_DATA_IDLE		BIT(16)
> > +#define   ASPEED_MDIO_DATA_MIIRDATA	GENMASK(15, 0)
> > +
> > +#define ASPEED_MDIO_RETRIES		10
> > +
> > +struct aspeed_mdio {
> > +	void __iomem *base;
> > +};
> > +
> > +static int aspeed_mdio_read(struct mii_bus *bus, int addr, int regnum)
> > +{
> > +	struct aspeed_mdio *ctx = bus->priv;
> > +	u32 ctrl;
> > +	int i;
> > +
> > +	dev_dbg(&bus->dev, "%s: addr: %d, regnum: %d\n", __func__, addr,
> > +		regnum);
> > +
> > +	/* Just clause 22 for the moment */
> > +	ctrl = ASPEED_MDIO_CTRL_FIRE
> 
> Hi Andrew
> 
> In the binding, you say C45 is supported. Here you don't. It would be
> nice to be consistent.

Right - but the bindings describe the hardware, and the hardware is capable.
Just that the driver as it stands can't drive it that way.

Having said that I do need to do more digging to understand how to cater to
C45 PHYs wrt the read/write calls.

> 
> 
> > +		| FIELD_PREP(ASPEED_MDIO_CTRL_ST, ASPEED_MDIO_CTRL_ST_C22)
> > +		| FIELD_PREP(ASPEED_MDIO_CTRL_OP, MDIO_C22_OP_READ)
> > +		| FIELD_PREP(ASPEED_MDIO_CTRL_PHYAD, addr)
> > +		| FIELD_PREP(ASPEED_MDIO_CTRL_REGAD, regnum);
> > +
> > +	iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL);
> > +
> > +	for (i = 0; i < ASPEED_MDIO_RETRIES; i++) {
> > +		u32 data;
> > +
> > +		data = ioread32(ctx->base + ASPEED_MDIO_DATA);
> > +		if (data & ASPEED_MDIO_DATA_IDLE)
> > +			return FIELD_GET(ASPEED_MDIO_DATA_MIIRDATA, data);
> > +
> > +		udelay(100);
> > +	}
> 
> One of the readx_poll_timeout functions could be used.

Thanks, I'll take a look.

> 
> > +
> > +	dev_err(&bus->dev, "MDIO read failed\n");
> > +	return -EIO;
> > +}
> > +
> > +static int aspeed_mdio_write(struct mii_bus *bus, int addr, int regnum, u16 val)
> > +{
> > +	struct aspeed_mdio *ctx = bus->priv;
> > +	u32 ctrl;
> > +	int i;
> > +
> > +	dev_dbg(&bus->dev, "%s: addr: %d, regnum: %d, val: 0x%x\n",
> > +		__func__, addr, regnum, val);
> > +
> > +	/* Just clause 22 for the moment */
> > +	ctrl = ASPEED_MDIO_CTRL_FIRE
> > +		| FIELD_PREP(ASPEED_MDIO_CTRL_ST, ASPEED_MDIO_CTRL_ST_C22)
> > +		| FIELD_PREP(ASPEED_MDIO_CTRL_OP, MDIO_C22_OP_WRITE)
> > +		| FIELD_PREP(ASPEED_MDIO_CTRL_PHYAD, addr)
> > +		| FIELD_PREP(ASPEED_MDIO_CTRL_REGAD, regnum)
> > +		| FIELD_PREP(ASPEED_MDIO_CTRL_MIIWDATA, val);
> > +
> > +	iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL);
> > +
> > +	for (i = 0; i < ASPEED_MDIO_RETRIES; i++) {
> > +		ctrl = ioread32(ctx->base + ASPEED_MDIO_CTRL);
> > +		if (!(ctrl & ASPEED_MDIO_CTRL_FIRE))
> > +			return 0;
> > +
> > +		udelay(100);
> > +	}
> 
> readx_poll_timeout() here as well.
> 
> Otherwise this looks good.

Thanks for the review!

Andrew
diff mbox series

Patch

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index 20f14c5fbb7e..206d8650ee7f 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -21,6 +21,19 @@  config MDIO_BUS
 
 if MDIO_BUS
 
+config MDIO_ASPEED
+	tristate "ASPEED MDIO bus controller"
+	depends on ARCH_ASPEED || COMPILE_TEST
+	depends on OF_MDIO && HAS_IOMEM
+	help
+	  This module provides a driver for the independent MDIO bus
+	  controllers found in the ASPEED AST2600 SoC. This is a driver for the
+	  third revision of the ASPEED MDIO register interface - the first two
+	  revisions are the "old" and "new" interfaces found in the AST2400 and
+	  AST2500, embedded in the MAC. For legacy reasons, FTGMAC100 driver
+	  continues to drive the embedded MDIO controller for the AST2400 and
+	  AST2500 SoCs, so say N if AST2600 support is not required.
+
 config MDIO_BCM_IPROC
 	tristate "Broadcom iProc MDIO bus controller"
 	depends on ARCH_BCM_IPROC || COMPILE_TEST
diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index 839acb292c38..ba07c27e4208 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile
@@ -22,6 +22,7 @@  libphy-$(CONFIG_LED_TRIGGER_PHY)	+= phy_led_triggers.o
 obj-$(CONFIG_PHYLINK)		+= phylink.o
 obj-$(CONFIG_PHYLIB)		+= libphy.o
 
+obj-$(CONFIG_MDIO_ASPEED)	+= mdio-aspeed.o
 obj-$(CONFIG_MDIO_BCM_IPROC)	+= mdio-bcm-iproc.o
 obj-$(CONFIG_MDIO_BCM_UNIMAC)	+= mdio-bcm-unimac.o
 obj-$(CONFIG_MDIO_BITBANG)	+= mdio-bitbang.o
diff --git a/drivers/net/phy/mdio-aspeed.c b/drivers/net/phy/mdio-aspeed.c
new file mode 100644
index 000000000000..71496a9ff54a
--- /dev/null
+++ b/drivers/net/phy/mdio-aspeed.c
@@ -0,0 +1,159 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Copyright (C) 2019 IBM Corp. */
+
+#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>
+
+#define DRV_NAME "mdio-aspeed"
+
+#define ASPEED_MDIO_CTRL		0x0
+#define   ASPEED_MDIO_CTRL_FIRE		BIT(31)
+#define   ASPEED_MDIO_CTRL_ST		BIT(28)
+#define     ASPEED_MDIO_CTRL_ST_C45	0
+#define     ASPEED_MDIO_CTRL_ST_C22	1
+#define   ASPEED_MDIO_CTRL_OP		GENMASK(27, 26)
+#define     MDIO_C22_OP_WRITE		0b01
+#define     MDIO_C22_OP_READ		0b10
+#define   ASPEED_MDIO_CTRL_PHYAD	GENMASK(25, 21)
+#define   ASPEED_MDIO_CTRL_REGAD	GENMASK(20, 16)
+#define   ASPEED_MDIO_CTRL_MIIWDATA	GENMASK(15, 0)
+
+#define ASPEED_MDIO_DATA		0x4
+#define   ASPEED_MDIO_DATA_MDC_THRES	GENMASK(31, 24)
+#define   ASPEED_MDIO_DATA_MDIO_EDGE	BIT(23)
+#define   ASPEED_MDIO_DATA_MDIO_LATCH	GENMASK(22, 20)
+#define   ASPEED_MDIO_DATA_IDLE		BIT(16)
+#define   ASPEED_MDIO_DATA_MIIRDATA	GENMASK(15, 0)
+
+#define ASPEED_MDIO_RETRIES		10
+
+struct aspeed_mdio {
+	void __iomem *base;
+};
+
+static int aspeed_mdio_read(struct mii_bus *bus, int addr, int regnum)
+{
+	struct aspeed_mdio *ctx = bus->priv;
+	u32 ctrl;
+	int i;
+
+	dev_dbg(&bus->dev, "%s: addr: %d, regnum: %d\n", __func__, addr,
+		regnum);
+
+	/* Just clause 22 for the moment */
+	ctrl = ASPEED_MDIO_CTRL_FIRE
+		| FIELD_PREP(ASPEED_MDIO_CTRL_ST, ASPEED_MDIO_CTRL_ST_C22)
+		| FIELD_PREP(ASPEED_MDIO_CTRL_OP, MDIO_C22_OP_READ)
+		| FIELD_PREP(ASPEED_MDIO_CTRL_PHYAD, addr)
+		| FIELD_PREP(ASPEED_MDIO_CTRL_REGAD, regnum);
+
+	iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL);
+
+	for (i = 0; i < ASPEED_MDIO_RETRIES; i++) {
+		u32 data;
+
+		data = ioread32(ctx->base + ASPEED_MDIO_DATA);
+		if (data & ASPEED_MDIO_DATA_IDLE)
+			return FIELD_GET(ASPEED_MDIO_DATA_MIIRDATA, data);
+
+		udelay(100);
+	}
+
+	dev_err(&bus->dev, "MDIO read failed\n");
+	return -EIO;
+}
+
+static int aspeed_mdio_write(struct mii_bus *bus, int addr, int regnum, u16 val)
+{
+	struct aspeed_mdio *ctx = bus->priv;
+	u32 ctrl;
+	int i;
+
+	dev_dbg(&bus->dev, "%s: addr: %d, regnum: %d, val: 0x%x\n",
+		__func__, addr, regnum, val);
+
+	/* Just clause 22 for the moment */
+	ctrl = ASPEED_MDIO_CTRL_FIRE
+		| FIELD_PREP(ASPEED_MDIO_CTRL_ST, ASPEED_MDIO_CTRL_ST_C22)
+		| FIELD_PREP(ASPEED_MDIO_CTRL_OP, MDIO_C22_OP_WRITE)
+		| FIELD_PREP(ASPEED_MDIO_CTRL_PHYAD, addr)
+		| FIELD_PREP(ASPEED_MDIO_CTRL_REGAD, regnum)
+		| FIELD_PREP(ASPEED_MDIO_CTRL_MIIWDATA, val);
+
+	iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL);
+
+	for (i = 0; i < ASPEED_MDIO_RETRIES; i++) {
+		ctrl = ioread32(ctx->base + ASPEED_MDIO_CTRL);
+		if (!(ctrl & ASPEED_MDIO_CTRL_FIRE))
+			return 0;
+
+		udelay(100);
+	}
+
+	dev_err(&bus->dev, "MDIO write failed\n");
+	return -EIO;
+}
+
+static int aspeed_mdio_probe(struct platform_device *pdev)
+{
+	struct aspeed_mdio *ctx;
+	struct mii_bus *bus;
+	int rc;
+
+	bus = devm_mdiobus_alloc_size(&pdev->dev, sizeof(*ctx));
+	if (!bus)
+		return -ENOMEM;
+
+	ctx = bus->priv;
+	ctx->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(ctx->base))
+		return PTR_ERR(ctx->base);
+
+	bus->name = DRV_NAME;
+	snprintf(bus->id, MII_BUS_ID_SIZE, "%s%d", pdev->name, pdev->id);
+	bus->parent = &pdev->dev;
+	bus->read = aspeed_mdio_read;
+	bus->write = aspeed_mdio_write;
+
+	rc = of_mdiobus_register(bus, pdev->dev.of_node);
+	if (rc) {
+		dev_err(&pdev->dev, "Cannot register MDIO bus!\n");
+		return rc;
+	}
+
+	platform_set_drvdata(pdev, bus);
+
+	return 0;
+}
+
+static int aspeed_mdio_remove(struct platform_device *pdev)
+{
+	mdiobus_unregister(platform_get_drvdata(pdev));
+
+	return 0;
+}
+
+static const struct of_device_id aspeed_mdio_of_match[] = {
+	{ .compatible = "aspeed,ast2600-mdio", },
+	{ },
+};
+
+static struct platform_driver aspeed_mdio_driver = {
+	.driver = {
+		.name = DRV_NAME,
+		.of_match_table = aspeed_mdio_of_match,
+	},
+	.probe = aspeed_mdio_probe,
+	.remove = aspeed_mdio_remove,
+};
+
+module_platform_driver(aspeed_mdio_driver);
+
+MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");
+MODULE_LICENSE("GPL");