Date:   Sun, 5 Feb 2017 14:44:54 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Christian Lamparter <chunkeey@...glemail.com>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org
Cc:     Christian Lamparter <chunkeey@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Ivan Mikhaylov <ivan@...ibm.com>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [RFC 2/2] net: emac: add support for device-tree based PHY
 discovery and setup

Le 02/05/17 à 14:25, Christian Lamparter a écrit :
> From: Christian Lamparter <chunkeey@...il.com>
> 
> This patch adds glue-code that allows the EMAC driver to interface
> with the existing dt-supported PHYs in drivers/net/phy.
> 
> Because currently, the emac driver maintains a small library of
> supported phys for in a private phy.c file located in the drivers
> directory.
> 
> The support is limited to mostly single ethernet transceiver like the:
> CIS8201, BCM5248, ET1011C, Marvell 88E1111 and 88E1112, AR8035.
> However, routers like the Netgear WNDR4700 and Cisco Meraki MX60(W)
> have a 5-port switch (QCA8327N) attached to the MDIO of the EMAC.
> The switch chip has already a proper phy-driver (qca8k) that uses
> the generic phy library.

Technically, it's a mdio_device in the upstream kernel that registers a
switch with DSA (and a PHY device in the OpenWrt/LEDE downstream
kernel). If your goal is to specifically support that device you should
consider making the EMAC interface with a fixed link PHY to properly
initialize the EMAC <=> CPU port of the switch link, and then declare
the qca8k device as a child MDIO device (not a PHY), similar to what is
done in arch/arm/boot/dts/vf610-zii-dev-rev-b.dts for instance.

> 
> Signed-off-by: Christian Lamparter <chunkeey@...glemail.com>
> ---
>  drivers/net/ethernet/ibm/emac/core.c | 188 +++++++++++++++++++++++++++++++++++
>  drivers/net/ethernet/ibm/emac/core.h |   4 +
>  2 files changed, 192 insertions(+)
> 
> diff --git a/drivers/net/ethernet/ibm/emac/core.c b/drivers/net/ethernet/ibm/emac/core.c
> index 6ead2335a169..ea9234cdb227 100644
> --- a/drivers/net/ethernet/ibm/emac/core.c
> +++ b/drivers/net/ethernet/ibm/emac/core.c
> @@ -42,6 +42,7 @@
>  #include <linux/of_address.h>
>  #include <linux/of_irq.h>
>  #include <linux/of_net.h>
> +#include <linux/of_mdio.h>
>  #include <linux/slab.h>
>  
>  #include <asm/processor.h>
> @@ -2420,6 +2421,179 @@ static int emac_read_uint_prop(struct device_node *np, const char *name,
>  	return 0;
>  }
>  
> +static void emac_adjust_link(struct net_device *ndev)
> +{
> +	struct emac_instance *dev = netdev_priv(ndev);
> +	struct phy_device *phy = dev->phy_dev;
> +
> +	mutex_lock(&dev->link_lock);
> +	dev->phy.autoneg = phy->autoneg;
> +	dev->phy.speed = phy->speed;
> +	dev->phy.duplex = phy->duplex;
> +	dev->phy.pause = phy->pause;
> +	dev->phy.asym_pause = phy->asym_pause;
> +	dev->phy.advertising = phy->advertising;
> +	mutex_unlock(&dev->link_lock);

PHYLIB already executes grabbing the phy device's mutex, is this really
needed here?

> +}
> +
> +static int emac_mii_bus_read(struct mii_bus *bus, int addr, int regnum)
> +{
> +	return emac_mdio_read(bus->priv, addr, regnum);
> +}
> +
> +static int emac_mii_bus_write(struct mii_bus *bus, int addr, int regnum,
> +			      u16 val)
> +{
> +	emac_mdio_write(bus->priv, addr, regnum, val);
> +	return 0;
> +}
> +
> +static int emac_mii_bus_reset(struct mii_bus *bus)
> +{
> +	struct emac_instance *dev = netdev_priv(bus->priv);
> +
> +	emac_mii_reset_phy(&dev->phy);

This seems wrong, emac_mii_reset_phy() does a BMCR software reset, which
PHYLIB is already going to do (phy_init_hw), yet you do this here at the
MDIO bus level towards a specify PHY, whereas this should be affecting
the MDIO bus itself (and/or *all* PHY child devices for quirks).

> +	return 0;
> +}
> +
> +static int emac_mdio_probe(struct emac_instance *dev)
> +{
> +	struct device_node *mii_np;
> +	struct mii_bus *bus;
> +	int res;
> +
> +	bus = mdiobus_alloc();
> +	if (!bus)
> +		return -ENOMEM;
> +
> +	mii_np = of_get_child_by_name(dev->ofdev->dev.of_node, "mdio");
> +	if (!mii_np) {
> +		dev_err(&dev->ndev->dev, "no mdio definition found.");
> +		return -ENODEV;
> +	}
> +
> +	if (!of_device_is_available(mii_np))
> +		return 0;
> +
> +	bus->priv = dev->ndev;
> +	bus->parent = dev->ndev->dev.parent;
> +	bus->name = "emac_mdio";
> +	bus->read = &emac_mii_bus_read;
> +	bus->write = &emac_mii_bus_write;
> +	bus->reset = &emac_mii_bus_reset;
> +
> +	snprintf(bus->id, MII_BUS_ID_SIZE, "%s", bus->name);

You should pick a more unique name here, if you ever have a second
instance it would just clash with the previous one.

> +
> +	res = of_mdiobus_register(bus, mii_np);
> +	if (res) {
> +		dev_err(&dev->ndev->dev, "cannot register MDIO bus %s\n",
> +			bus->name);
> +		mdiobus_free(bus);
> +	}
> +
> +	dev->mii_bus = bus;
> +	return res;
> +}
> +
> +static void emac_mdio_cleanup(struct emac_instance *dev)
> +{
> +	if (dev->mii_bus) {
> +		if (dev->mii_bus->state == MDIOBUS_REGISTERED)
> +			mdiobus_unregister(dev->mii_bus);

If you need to make that kind of check, why not separate how the mdio
bus structure's lifecycle is managed? This seems to be avoiding to hit
the BUG_ON() in mdiobus_unregister..

> +		mdiobus_free(dev->mii_bus);
> +		dev->mii_bus = NULL;
> +		kfree(dev->phy.def);
> +	}
> +}
> +
> +static int stub_setup_aneg(struct mii_phy *phy, u32 advertise)
> +{
> +	return 0;
> +}
> +
> +static int stub_setup_forced(struct mii_phy *phy, int speed, int fd)
> +{
> +	return 0;
> +}
> +
> +static int stub_poll_link(struct mii_phy *phy)
> +{
> +	struct net_device *ndev = phy->dev;
> +	struct emac_instance *dev = netdev_priv(ndev);
> +
> +	return dev->opened;
> +}
> +
> +static int stub_read_link(struct mii_phy *phy)
> +{
> +	struct net_device *ndev = phy->dev;
> +	struct emac_instance *dev = netdev_priv(ndev);
> +
> +	phy_start(dev->phy_dev);

Are you sure the read_link function is supposed to start the PHY state
machine? Either the name is confusing, or it's not the right thing to do
here.

> +	return 0;
> +}
> +
> +static const struct mii_phy_ops emac_stub_phy_ops = {
> +	.setup_aneg	= stub_setup_aneg,
> +	.setup_forced	= stub_setup_forced,
> +	.poll_link	= stub_poll_link,
> +	.read_link	= stub_read_link,
> +};
> +
> +static int emac_probe_dt_phy(struct emac_instance *dev)
> +{
> +	struct device_node *np = dev->ofdev->dev.of_node;
> +	struct device_node *phy_handle;
> +	struct net_device *ndev = dev->ndev;
> +	int res;
> +
> +	phy_handle = of_parse_phandle(np, "phy-handle", 0);
> +
> +	if (phy_handle) {
> +		res = emac_mdio_probe(dev);
> +		if (res)
> +			goto err_cleanup;
> +
> +		dev->phy.def = kzalloc(sizeof(*dev->phy.def), GFP_KERNEL);
> +		if (!dev->phy.def) {
> +			res = -ENOMEM;
> +			goto err_cleanup;
> +		}
> +
> +		dev->phy_dev = of_phy_connect(ndev, phy_handle,
> +					      &emac_adjust_link, 0,
> +					      PHY_INTERFACE_MODE_RGMII);

You should call of_get_phy_mode() since there should be a proper
"phy-mode" or "phy-connection-type" property describing how it's
connected to the EMAC.

> +		if (!dev->phy_dev) {
> +			res = -ENODEV;
> +			goto err_cleanup;
> +		}
> +
> +		of_node_put(phy_handle);
> +		dev->phy.def->phy_id = dev->phy_dev->drv->phy_id;
> +		dev->phy.def->phy_id_mask = dev->phy_dev->drv->phy_id_mask;
> +		dev->phy.def->name = dev->phy_dev->drv->name;
> +		dev->phy.def->ops = &emac_stub_phy_ops;
> +		/* Disable any PHY features not supported by the platform */
> +		dev->phy.def->features =  dev->phy_dev->drv->features &
> +					  ~dev->phy_feat_exc;
> +		dev->phy.features = dev->phy.def->features;
> +		dev->phy.address = dev->phy_dev->mdio.addr;
> +		dev->phy.mode = dev->phy_dev->interface;
> +		return 0;
> +	}
> +
> +	/* if the device tree didn't specifiy the the phy, then
> +	 * we simply fallback to the old emac_phy.c probe code
> +	 * for compatibility reasons.
> +	 */
> +	return 1;
> +
> + err_cleanup:
> +	of_node_put(phy_handle);
> +	kfree(dev->phy.def);
> +	return res;
> +}
> +
>  static int emac_init_phy(struct emac_instance *dev)
>  {
>  	struct device_node *np = dev->ofdev->dev.of_node;
> @@ -2490,6 +2664,13 @@ static int emac_init_phy(struct emac_instance *dev)
>  
>  	emac_configure(dev);
>  
> +	if (emac_has_feature(dev, EMAC_FTR_HAS_RGMII)) {
> +		int res = emac_probe_dt_phy(dev);
> +
> +		if (res <= 0)
> +			return res;
> +	}

Why is this limited to EMAC_FTR_HAS_RGMII here?

> +
>  	if (dev->phy_address != 0xffffffff)
>  		phy_map = ~(1 << dev->phy_address);
>  
> @@ -2938,6 +3119,8 @@ static int emac_probe(struct platform_device *ofdev)
>  	/* I have a bad feeling about this ... */
>  
>   err_detach_tah:
> +	emac_mdio_cleanup(dev);
> +
>  	if (emac_has_feature(dev, EMAC_FTR_HAS_TAH))
>  		tah_detach(dev->tah_dev, dev->tah_port);
>   err_detach_rgmii:
> @@ -2988,6 +3171,11 @@ static int emac_remove(struct platform_device *ofdev)
>  	if (emac_has_feature(dev, EMAC_FTR_HAS_ZMII))
>  		zmii_detach(dev->zmii_dev, dev->zmii_port);
>  
> +	if (dev->phy_dev)
> +		phy_disconnect(dev->phy_dev);
> +
> +	emac_mdio_cleanup(dev);
> +
>  	busy_phy_map &= ~(1 << dev->phy.address);
>  	DBG(dev, "busy_phy_map now %#x" NL, busy_phy_map);
>  
> diff --git a/drivers/net/ethernet/ibm/emac/core.h b/drivers/net/ethernet/ibm/emac/core.h
> index 93ae11494810..0710a6685489 100644
> --- a/drivers/net/ethernet/ibm/emac/core.h
> +++ b/drivers/net/ethernet/ibm/emac/core.h
> @@ -199,6 +199,10 @@ struct emac_instance {
>  	struct emac_instance		*mdio_instance;
>  	struct mutex			mdio_lock;
>  
> +	/* Device-tree based phy configuration */
> +	struct mii_bus			*mii_bus;
> +	struct phy_device		*phy_dev;
> +
>  	/* ZMII infos if any */
>  	u32				zmii_ph;
>  	u32				zmii_port;
> 


-- 
Florian

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