netdev - Re: [PATCH] smsc95xx: Add support for automated PHY address detection

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Date:   Sun, 23 Dec 2018 10:30:25 +0100
From:   Marek Vasut <marex@...x.de>
To:     linux-usb@...r.kernel.org
Cc:     "David S . Miller" <davem@...emloft.net>,
        Nisar Sayed <Nisar.Sayed@...rochip.com>,
        Woojung Huh <Woojung.Huh@...rochip.com>,
        netdev <netdev@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH] smsc95xx: Add support for automated PHY address detection

On 9/11/18 12:12 PM, Marek Vasut wrote:
> The SMSC95xx chip can use either the internal PHY or an external one.
> Currently, the driver hard-codes support for the internal PHY only.
> 
> This patch reads out the HW_CFG register to determine whether external
> PHY is attached or not. If an external PHY is not attached, the driver
> falls back to internal PHY with fixed PHY address 0x1.
> 
> If an external PHY is attached, the driver scans the entire address
> range of the MDIO bus to determine whether there is a valid external
> PHY attached. The scanning happens from the end of the address range,
> since some PHYs also respond to address 0, which is considered a MDIO
> broadcast address by them. We want to obtain their real MDIO address
> instead.
> 
> Signed-off-by: Marek Vasut <marex@...x.de>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: Nisar Sayed <Nisar.Sayed@...rochip.com>
> Cc: Woojung Huh <Woojung.Huh@...rochip.com>

Expanding the CC, since I received no feedback.
Still applies cleanly on next/master.

> ---
>  drivers/net/usb/smsc95xx.c | 42 +++++++++++++++++++++++++++++++++++++-
>  1 file changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
> index 06b4d290784d..014bb71ce8a8 100644
> --- a/drivers/net/usb/smsc95xx.c
> +++ b/drivers/net/usb/smsc95xx.c
> @@ -983,6 +983,40 @@ static int smsc95xx_start_rx_path(struct usbnet *dev, int in_pm)
>  	return __smsc95xx_write_reg(dev, MAC_CR, pdata->mac_cr, in_pm);
>  }
>  
> +static int smsc95xx_phy_address(struct usbnet *dev)
> +{
> +	u32 read_buf;
> +	int ret, id1, id2, phyad;
> +
> +	ret = smsc95xx_read_reg(dev, HW_CFG, &read_buf);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Check if using external PHY, if not, use internal PHY address */
> +	if (!(read_buf & HW_CFG_PSEL_))
> +		return SMSC95XX_INTERNAL_PHY_ID;
> +
> +	/*
> +	 * Detect external PHY address. Here we probe the MDIO bus from
> +	 * the highest address, since some PHYs respond also on address
> +	 * zero, which they consider MDIO broadcast address. We really
> +	 * want to get their proper address instead though, so we scan
> +	 * address zero last.
> +	 */
> +	for (phyad = 0x1f; phyad >= 0; phyad--) {
> +		id1 = smsc95xx_mdio_read(dev->net, phyad, MII_PHYSID1);
> +		id2 = smsc95xx_mdio_read(dev->net, phyad, MII_PHYSID2);
> +		/* Check for valid response from the PHY */
> +		if (id1 > 0 && id2 > 0 && id1 != 0x7fff && id2 != 0xffff)
> +			return phyad;
> +	}
> +
> +	/* No PHY found. */
> +	netdev_warn(dev->net, "cannot detect any PHY");
> +
> +	return -ENODEV;
> +}
> +
>  static int smsc95xx_phy_initialize(struct usbnet *dev)
>  {
>  	int bmcr, ret, timeout = 0;
> @@ -993,7 +1027,13 @@ static int smsc95xx_phy_initialize(struct usbnet *dev)
>  	dev->mii.mdio_write = smsc95xx_mdio_write;
>  	dev->mii.phy_id_mask = 0x1f;
>  	dev->mii.reg_num_mask = 0x1f;
> -	dev->mii.phy_id = SMSC95XX_INTERNAL_PHY_ID;
> +
> +	/* Determine PHY address */
> +	ret = smsc95xx_phy_address(dev);
> +	if (ret)
> +		return ret;
> +
> +	dev->mii.phy_id = ret;
>  
>  	/* reset phy and wait for reset to complete */
>  	smsc95xx_mdio_write(dev->net, dev->mii.phy_id, MII_BMCR, BMCR_RESET);
>