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

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Message-ID: <CA+HBbNEYkQKy-WjxB+QDasknH8gAChddcbtNX6xxE3a+GoNC2g@mail.gmail.com>
Date:   Wed, 15 Apr 2020 17:07:17 +0200
From:   Robert Marko <robert.marko@...tura.hr>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        robh+dt@...nel.org, Mark Rutland <mark.rutland@....com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        devicetree@...r.kernel.org,
        Christian Lamparter <chunkeey@...il.com>,
        Luka Perkov <luka.perkov@...tura.hr>
Subject: Re: [PATCH v2 1/3] net: phy: mdio: add IPQ40xx MDIO driver

I have sent a v3.

I tried to incorporate all of your remarks there.

Thanks
Robert

On Wed, Apr 15, 2020 at 11:33 AM Russell King - ARM Linux admin
<linux@...linux.org.uk> wrote:
>
> 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.
>
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line in suburbia: sync at 10.2Mbps down 587kbps up