Subject: Re: [PATCH v2 1/3] net: phy: mdio: add IPQ40xx MDIO driver

From: Russell King - ARM Linux admin <[email-masked]>
Date: Wed, 15 Apr 2020 10:33:34 +0100

On Tue, Apr 14, 2020 at 08:10:11PM +0200, Robert Marko wrote:
> diff --git a/drivers/net/phy/mdio-ipq40xx.c b/drivers/net/phy/mdio-ipq40xx.c
> new file mode 100644
> index 000000000000..d8c11c621f20
> --- /dev/null
> +++ b/drivers/net/phy/mdio-ipq40xx.c
> @@ -0,0 +1,176 @@
> +// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
> +/* Copyright (c) 2015, The Linux Foundation. All rights reserved. */
> +/* Copyright (c) 2020 Sartura Ltd. */
> +
> +#include <linux/delay.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/io.h>
> +#include <linux/of_address.h>
> +#include <linux/of_mdio.h>
> +#include <linux/phy.h>
> +#include <linux/platform_device.h>
> +

Looking at how these registers are used, they could be renamed:

> +#define MDIO_CTRL_0_REG		0x40

This seems to be unused.

> +#define MDIO_CTRL_1_REG		0x44

MDIO_ADDR_REG

> +#define MDIO_CTRL_2_REG		0x48

MDIO_DATA_WRITE_REG

> +#define MDIO_CTRL_3_REG		0x4c

MDIO_DATA_READ_REG

> +#define MDIO_CTRL_4_REG		0x50
> +#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

MDIO_CMD_* ?

> +
> +#define IPQ40XX_MDIO_RETRY	1000
> +#define IPQ40XX_MDIO_DELAY	10
> +
> +struct ipq40xx_mdio_data {
> +	void __iomem	*membase;
> +};
> +
> +static int ipq40xx_mdio_wait_busy(struct mii_bus *bus)
> +{
> +	struct ipq40xx_mdio_data *priv = bus->priv;
> +	int i;
> +
> +	for (i = 0; i < IPQ40XX_MDIO_RETRY; i++) {
> +		unsigned int busy;
> +
> +		busy = readl(priv->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(bus->parent, "MDIO operation timed out\n");
> +
> +	return -ETIMEDOUT;
> +}
> +
> +static int ipq40xx_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
> +{
> +	struct ipq40xx_mdio_data *priv = bus->priv;
> +	int value = 0;
> +	unsigned int cmd = 0;

No need to initialise either of these, and you can eliminate "value"
which will then satisfy davem's requirement for reverse-christmas-tree
ordering of variable declarations.

> +
> +	/* Reject clause 45 */
> +	if (regnum & MII_ADDR_C45)
> +		return -EOPNOTSUPP;
> +
> +	if (ipq40xx_mdio_wait_busy(bus))
> +		return -ETIMEDOUT;
> +
> +	/* issue the phy address and reg */
> +	writel((mii_id << 8) | regnum, priv->membase + MDIO_CTRL_1_REG);
> +
> +	cmd = MDIO_CTRL_4_ACCESS_START | MDIO_CTRL_4_ACCESS_CODE_READ;
> +
> +	/* issue read command */
> +	writel(cmd, priv->membase + MDIO_CTRL_4_REG);
> +
> +	/* Wait read complete */
> +	if (ipq40xx_mdio_wait_busy(bus))
> +		return -ETIMEDOUT;
> +
> +	/* Read data */
> +	value = readl(priv->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 *priv = bus->priv;
> +	unsigned int cmd = 0;

No need to initialise cmd.

-- 
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