Re: [PATCH 1/2] net: mdio: add ipq8064 mdio driver

[Russell King - ARM Linux admin <linux@armlinux.org.uk>]

On Thu, Feb 20, 2020 at 04:12:55PM +0100, Ansuel Smith wrote:
> Currently ipq806x soc use generi bitbang driver to
> comunicate with the gmac ethernet interface.
> Add a dedicated driver created by chunkeey to fix this.
> 
> Christian Lamparter <chunkeey@gmail.com>
> Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
> ---
>  drivers/net/phy/Kconfig        |   8 ++
>  drivers/net/phy/Makefile       |   1 +
>  drivers/net/phy/mdio-ipq8064.c | 163 +++++++++++++++++++++++++++++++++
>  3 files changed, 172 insertions(+)
>  create mode 100644 drivers/net/phy/mdio-ipq8064.c
> 
> diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
> index 9dabe03a668c..ec2a5493a7e8 100644
> --- a/drivers/net/phy/Kconfig
> +++ b/drivers/net/phy/Kconfig
> @@ -157,6 +157,14 @@ config MDIO_I2C
>  
>  	  This is library mode.
>  
> +config MDIO_IPQ8064
> +	tristate "Qualcomm IPQ8064 MDIO interface support"
> +	depends on HAS_IOMEM && OF_MDIO
> +	depends on MFD_SYSCON
> +	help
> +	  This driver supports the MDIO interface found in the network
> +	  interface units of the IPQ8064 SoC
> +
>  config MDIO_MOXART
>  	tristate "MOXA ART MDIO interface support"
>  	depends on ARCH_MOXART || COMPILE_TEST
> diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
> index fe5badf13b65..8f02bd2089f3 100644
> --- a/drivers/net/phy/Makefile
> +++ b/drivers/net/phy/Makefile
> @@ -36,6 +36,7 @@ obj-$(CONFIG_MDIO_CAVIUM)	+= mdio-cavium.o
>  obj-$(CONFIG_MDIO_GPIO)		+= mdio-gpio.o
>  obj-$(CONFIG_MDIO_HISI_FEMAC)	+= mdio-hisi-femac.o
>  obj-$(CONFIG_MDIO_I2C)		+= mdio-i2c.o
> +obj-$(CONFIG_MDIO_IPQ8064)	+= mdio-ipq8064.o
>  obj-$(CONFIG_MDIO_MOXART)	+= mdio-moxart.o
>  obj-$(CONFIG_MDIO_MSCC_MIIM)	+= mdio-mscc-miim.o
>  obj-$(CONFIG_MDIO_OCTEON)	+= mdio-octeon.o
> diff --git a/drivers/net/phy/mdio-ipq8064.c b/drivers/net/phy/mdio-ipq8064.c
> new file mode 100644
> index 000000000000..c76e6a647787
> --- /dev/null
> +++ b/drivers/net/phy/mdio-ipq8064.c
> @@ -0,0 +1,163 @@
> +// SPDX-License-Identifier: GPL-2.0
> +//
> +// Qualcomm IPQ8064 MDIO interface driver
> +//
> +// Copyright (C) 2019 Christian Lamparter <chunkeey@gmail.com>
> +
> +#include <linux/delay.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/regmap.h>
> +#include <linux/of_mdio.h>
> +#include <linux/phy.h>
> +#include <linux/platform_device.h>
> +#include <linux/mfd/syscon.h>
> +
> +/* MII address register definitions */
> +#define MII_ADDR_REG_ADDR                       0x10
> +#define MII_BUSY                                BIT(0)
> +#define MII_WRITE                               BIT(1)
> +#define MII_CLKRANGE_60_100M                    (0 << 2)
> +#define MII_CLKRANGE_100_150M                   (1 << 2)
> +#define MII_CLKRANGE_20_35M                     (2 << 2)
> +#define MII_CLKRANGE_35_60M                     (3 << 2)
> +#define MII_CLKRANGE_150_250M                   (4 << 2)
> +#define MII_CLKRANGE_250_300M                   (5 << 2)
> +#define MII_CLKRANGE_MASK			GENMASK(4, 2)
> +#define MII_REG_SHIFT				6
> +#define MII_REG_MASK				GENMASK(10, 6)
> +#define MII_ADDR_SHIFT				11
> +#define MII_ADDR_MASK				GENMASK(15, 11)
> +
> +#define MII_DATA_REG_ADDR                       0x14
> +
> +#define MII_MDIO_DELAY                          (1000)
> +#define MII_MDIO_RETRY                          (10)
> +
> +struct ipq8064_mdio {
> +	struct regmap *base; /* NSS_GMAC0_BASE */
> +};
> +
> +static int
> +ipq8064_mdio_wait_busy(struct ipq8064_mdio *priv)
> +{
> +	int i;
> +
> +	for (i = 0; i < MII_MDIO_RETRY; i++) {
> +		unsigned int busy;
> +
> +		regmap_read(priv->base, MII_ADDR_REG_ADDR, &busy);
> +		if (!(busy & MII_BUSY))
> +			return 0;
> +
> +		udelay(MII_MDIO_DELAY);
> +	}

On the last loop, this will delay MII_MDIO_DELAY and then return
-ETIMEDOUT, which is not nice behaviour.  Have you considered using
regmap_read_poll_timeout() here?

> +
> +	return -ETIMEDOUT;
> +}
> +
> +static int
> +ipq8064_mdio_read(struct mii_bus *bus, int phy_addr, int reg_offset)
> +{
> +	struct ipq8064_mdio *priv = bus->priv;
> +	u32 miiaddr = MII_BUSY | MII_CLKRANGE_250_300M;
> +	u32 ret_val;
> +	int err;
> +
> +	miiaddr |= ((phy_addr << MII_ADDR_SHIFT) & MII_ADDR_MASK) |
> +		   ((reg_offset << MII_REG_SHIFT) & MII_REG_MASK);

This looks like it only supports Clause 22 accesses, so shouldn't it
reject Clause 45 accesses (signified by reg_offset & MII_ADDR_C45) ?

> +	regmap_write(priv->base, MII_ADDR_REG_ADDR, miiaddr);
> +	usleep_range(10, 20);
> +
> +	err = ipq8064_mdio_wait_busy(priv);
> +	if (err)
> +		return err;
> +
> +	regmap_read(priv->base, MII_DATA_REG_ADDR, &ret_val);
> +	return (int)ret_val;
> +}
> +
> +static int
> +ipq8064_mdio_write(struct mii_bus *bus, int phy_addr, int reg_offset, u16 data)
> +{
> +	struct ipq8064_mdio *priv = bus->priv;
> +	u32 miiaddr = MII_WRITE | MII_BUSY | MII_CLKRANGE_250_300M;
> +
> +	regmap_write(priv->base, MII_DATA_REG_ADDR, data);
> +
> +	miiaddr |= ((phy_addr << MII_ADDR_SHIFT) & MII_ADDR_MASK) |
> +		   ((reg_offset << MII_REG_SHIFT) & MII_REG_MASK);

Same here as for ipq8064_mdio_read().

> +
> +	regmap_write(priv->base, MII_ADDR_REG_ADDR, miiaddr);
> +	usleep_range(10, 20);
> +
> +	return ipq8064_mdio_wait_busy(priv);
> +}
> +
> +static int
> +ipq8064_mdio_probe(struct platform_device *pdev)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	struct ipq8064_mdio *priv;
> +	struct mii_bus *bus;
> +	int ret;
> +
> +	bus = devm_mdiobus_alloc_size(&pdev->dev, sizeof(*priv));
> +	if (!bus)
> +		return -ENOMEM;
> +
> +	bus->name = "ipq8064_mdio_bus";
> +	bus->read = ipq8064_mdio_read;
> +	bus->write = ipq8064_mdio_write;
> +	snprintf(bus->id, MII_BUS_ID_SIZE, "%s-mii", dev_name(&pdev->dev));
> +	bus->parent = &pdev->dev;
> +
> +	priv = bus->priv;
> +	priv->base = syscon_node_to_regmap(np);
> +	if (IS_ERR_OR_NULL(priv->base)) {
> +		priv->base = syscon_regmap_lookup_by_phandle(np, "master");
> +		if (IS_ERR_OR_NULL(priv->base)) {
> +			pr_err("master phandle not found\n");
> +			return -EINVAL;
> +		}
> +	}

Does syscon_node_to_regmap() return NULL?  From what I can see in
drivers/mfd/syscon.c, both that and syscon_regmap_lookup_by_phandle()
returns an error pointer, and if there's an error code, it should be
propagated.

Using dev_err(&pdev->dev, ...) for that error print is also nice -
imagine a kernel log where you have a line appear that only says
"master phandle not found" - you don't know where in the kernel it
came from, or even what device it's referring to.

> +
> +	ret = of_mdiobus_register(bus, np);
> +	if (ret)
> +		return ret;
> +
> +	platform_set_drvdata(pdev, bus);
> +	return 0;
> +}
> +
> +static int
> +ipq8064_mdio_remove(struct platform_device *pdev)
> +{
> +	struct mii_bus *bus = platform_get_drvdata(pdev);
> +
> +	mdiobus_unregister(bus);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id ipq8064_mdio_dt_ids[] = {
> +	{ .compatible = "qcom,ipq8064-mdio" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, ipq8064_mdio_dt_ids);
> +
> +static struct platform_driver ipq8064_mdio_driver = {
> +	.probe = ipq8064_mdio_probe,
> +	.remove = ipq8064_mdio_remove,
> +	.driver = {
> +		.name = "ipq8064-mdio",
> +		.of_match_table = ipq8064_mdio_dt_ids,
> +	},
> +};
> +
> +module_platform_driver(ipq8064_mdio_driver);
> +
> +MODULE_DESCRIPTION("Qualcomm IPQ8064 MDIO interface driver");
> +MODULE_AUTHOR("Christian Lamparter <chunkeey@gmail.com>");
> +MODULE_LICENSE("GPL");
> -- 
> 2.25.0
> 
> 

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