linux-kernel - Re: [PATCH 1/3] net: phy: mdio: add IPQ40xx MDIO driver

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Date:   Mon, 13 Apr 2020 20:42:19 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Robert Marko <robert.marko@...tura.hr>
Cc:     f.fainelli@...il.com, hkallweit1@...il.com, linux@...linux.org.uk,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        agross@...nel.org, bjorn.andersson@...aro.org, robh+dt@...nel.org,
        mark.rutland@....com, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org,
        Christian Lamparter <chunkeey@...il.com>,
        Luka Perkov <luka.perkov@...tura.hr>
Subject: Re: [PATCH 1/3] net: phy: mdio: add IPQ40xx MDIO driver

> --- 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-$(CONFIG_MDIO_IPQ40XX)	+= mdio-ipq40xx.o
>  obj-$(CONFIG_MDIO_MOXART)	+= mdio-moxart.o
>  obj-$(CONFIG_MDIO_MSCC_MIIM)	+= mdio-mscc-miim.o

Hi Robert

That looks odd. What happened to the

obj-$(CONFIG_MDIO_IPQ8064)      += mdio-ipq8064.o

>  obj-$(CONFIG_MDIO_OCTEON)	+= mdio-octeon.o
> diff --git a/drivers/net/phy/mdio-ipq40xx.c b/drivers/net/phy/mdio-ipq40xx.c
> new file mode 100644
> index 000000000000..8068f1e6a077
> --- /dev/null
> +++ b/drivers/net/phy/mdio-ipq40xx.c
> @@ -0,0 +1,180 @@
> +// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
> +/* Copyright (c) 2015, The Linux Foundation. All rights reserved. */
> +
> +#include <linux/delay.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/io.h>
> +#include <linux/of_address.h>
> +#include <linux/of_mdio.h>
> +#include <linux/phy.h>
> +#include <linux/platform_device.h>
> +
> +#define MDIO_CTRL_0_REG		0x40
> +#define MDIO_CTRL_1_REG		0x44
> +#define MDIO_CTRL_2_REG		0x48
> +#define MDIO_CTRL_3_REG		0x4c
> +#define MDIO_CTRL_4_REG		0x50

Can we have better names than as. It seems like 3 is read data, 2 is
write data, etc.

> +#define MDIO_CTRL_4_ACCESS_BUSY		BIT(16)
> +#define MDIO_CTRL_4_ACCESS_START		BIT(8)
> +#define MDIO_CTRL_4_ACCESS_CODE_READ		0
> +#define MDIO_CTRL_4_ACCESS_CODE_WRITE	1
> +#define CTRL_0_REG_DEFAULT_VALUE	0x150FF

No magic numbers please. Try to explain what each of these bits
do. I'm guessing they are clock speed, preamble enable, maybe C22/C45?

> +
> +#define IPQ40XX_MDIO_RETRY	1000
> +#define IPQ40XX_MDIO_DELAY	10
> +
> +struct ipq40xx_mdio_data {
> +	struct mii_bus	*mii_bus;
> +	void __iomem	*membase;
> +	struct device	*dev;
> +};
> +
> +static int ipq40xx_mdio_wait_busy(struct ipq40xx_mdio_data *am)
> +{
> +	int i;
> +
> +	for (i = 0; i < IPQ40XX_MDIO_RETRY; i++) {
> +		unsigned int busy;
> +
> +		busy = readl(am->membase + MDIO_CTRL_4_REG) &
> +			MDIO_CTRL_4_ACCESS_BUSY;
> +		if (!busy)
> +			return 0;
> +
> +		/* BUSY might take to be cleard by 15~20 times of loop */
> +		udelay(IPQ40XX_MDIO_DELAY);
> +	}
> +
> +	dev_err(am->dev, "%s: MDIO operation timed out\n", am->mii_bus->name);

dev_err() should give you enough to identify the device. No need to
print am->mii_bus->name as well.

> +
> +	return -ETIMEDOUT;
> +}
> +
> +static int ipq40xx_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
> +{
> +	struct ipq40xx_mdio_data *am = bus->priv;
> +	int value = 0;
> +	unsigned int cmd = 0;
> +
> +	lockdep_assert_held(&bus->mdio_lock);

Do you think the core is broken?

Please check if the request is for a C45 read, and return -EOPNOTSUPP
if so.


> +
> +	if (ipq40xx_mdio_wait_busy(am))
> +		return -ETIMEDOUT;
> +
> +	/* issue the phy address and reg */
> +	writel((mii_id << 8) | regnum, am->membase + MDIO_CTRL_1_REG);
> +
> +	cmd = MDIO_CTRL_4_ACCESS_START | MDIO_CTRL_4_ACCESS_CODE_READ;
> +
> +	/* issue read command */
> +	writel(cmd, am->membase + MDIO_CTRL_4_REG);
> +
> +	/* Wait read complete */
> +	if (ipq40xx_mdio_wait_busy(am))
> +		return -ETIMEDOUT;
> +
> +	/* Read data */
> +	value = readl(am->membase + MDIO_CTRL_3_REG);
> +
> +	return value;
> +}
> +
> +static int ipq40xx_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
> +							 u16 value)
> +{
> +	struct ipq40xx_mdio_data *am = bus->priv;
> +	unsigned int cmd = 0;
> +
> +	lockdep_assert_held(&bus->mdio_lock);
> +
> +	if (ipq40xx_mdio_wait_busy(am))
> +		return -ETIMEDOUT;
> +
> +	/* issue the phy address and reg */
> +	writel((mii_id << 8) | regnum, am->membase + MDIO_CTRL_1_REG);
> +
> +	/* issue write data */
> +	writel(value, am->membase + MDIO_CTRL_2_REG);
> +
> +	cmd = MDIO_CTRL_4_ACCESS_START | MDIO_CTRL_4_ACCESS_CODE_WRITE;
> +	/* issue write command */
> +	writel(cmd, am->membase + MDIO_CTRL_4_REG);
> +
> +	/* Wait write complete */
> +	if (ipq40xx_mdio_wait_busy(am))
> +		return -ETIMEDOUT;
> +
> +	return 0;
> +}
> +
> +static int ipq40xx_mdio_probe(struct platform_device *pdev)
> +{
> +	struct ipq40xx_mdio_data *am;

Why the name am? Generally priv is used. I could also understand bus,
or even data, but am?

   Andrew