Re: [RFC PATCH 5/6] net: marvell: neta: add support for 2500base-X

[Russell King - ARM Linux <linux@armlinux.org.uk>]

On Wed, Nov 14, 2018 at 02:18:14PM +0530, Kishon Vijay Abraham I wrote:
> Hi,
> 
> On 12/11/18 6:01 PM, Russell King wrote:
> > Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
> > ---
> >  drivers/net/ethernet/marvell/mvneta.c | 58 ++++++++++++++++++++++++++++++-----
> >  1 file changed, 51 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> > index 5bfd349bf41a..7305d4cc0630 100644
> > --- a/drivers/net/ethernet/marvell/mvneta.c
> > +++ b/drivers/net/ethernet/marvell/mvneta.c
> > @@ -27,6 +27,7 @@
> >  #include <linux/of_irq.h>
> >  #include <linux/of_mdio.h>
> >  #include <linux/of_net.h>
> > +#include <linux/phy/phy.h>
> >  #include <linux/phy.h>
> >  #include <linux/phylink.h>
> >  #include <linux/platform_device.h>
> > @@ -437,6 +438,7 @@ struct mvneta_port {
> >  	struct device_node *dn;
> >  	unsigned int tx_csum_limit;
> >  	struct phylink *phylink;
> > +	struct phy *comphy;
> >  
> >  	struct mvneta_bm *bm_priv;
> >  	struct mvneta_bm_pool *pool_long;
> > @@ -3150,6 +3152,8 @@ static void mvneta_start_dev(struct mvneta_port *pp)
> >  {
> >  	int cpu;
> >  
> > +	WARN_ON(phy_power_on(pp->comphy));
> > +
> >  	mvneta_max_rx_size_set(pp, pp->pkt_size);
> >  	mvneta_txq_max_tx_size_set(pp, pp->pkt_size);
> >  
> > @@ -3212,6 +3216,8 @@ static void mvneta_stop_dev(struct mvneta_port *pp)
> >  
> >  	mvneta_tx_reset(pp);
> >  	mvneta_rx_reset(pp);
> > +
> > +	WARN_ON(phy_power_off(pp->comphy));
> >  }
> >  
> >  static void mvneta_percpu_enable(void *arg)
> > @@ -3337,6 +3343,7 @@ static int mvneta_set_mac_addr(struct net_device *dev, void *addr)
> >  static void mvneta_validate(struct net_device *ndev, unsigned long *supported,
> >  			    struct phylink_link_state *state)
> >  {
> > +	struct mvneta_port *pp = netdev_priv(ndev);
> >  	__ETHTOOL_DECLARE_LINK_MODE_MASK(mask) = { 0, };
> >  
> >  	/* We only support QSGMII, SGMII, 802.3z and RGMII modes */
> > @@ -3357,14 +3364,14 @@ static void mvneta_validate(struct net_device *ndev, unsigned long *supported,
> >  	/* Asymmetric pause is unsupported */
> >  	phylink_set(mask, Pause);
> >  
> > -	/* We cannot use 1Gbps when using the 2.5G interface. */
> > -	if (state->interface == PHY_INTERFACE_MODE_2500BASEX) {
> > -		phylink_set(mask, 2500baseT_Full);
> > -		phylink_set(mask, 2500baseX_Full);
> > -	} else {
> > +	/* Half-duplex at speeds higher than 100Mbit is unsupported */
> > +	if (pp->comphy || state->interface != PHY_INTERFACE_MODE_2500BASEX) {
> >  		phylink_set(mask, 1000baseT_Full);
> >  		phylink_set(mask, 1000baseX_Full);
> >  	}
> > +	if (pp->comphy || state->interface == PHY_INTERFACE_MODE_2500BASEX) {
> > +		phylink_set(mask, 2500baseX_Full);
> > +	}
> >  
> >  	if (!phy_interface_mode_is_8023z(state->interface)) {
> >  		/* 10M and 100M are only supported in non-802.3z mode */
> > @@ -3378,6 +3385,11 @@ static void mvneta_validate(struct net_device *ndev, unsigned long *supported,
> >  		   __ETHTOOL_LINK_MODE_MASK_NBITS);
> >  	bitmap_and(state->advertising, state->advertising, mask,
> >  		   __ETHTOOL_LINK_MODE_MASK_NBITS);
> > +
> > +	/* We can only operate at 2500BaseX or 1000BaseX.  If requested
> > +	 * to advertise both, only report advertising at 2500BaseX.
> > +	 */
> > +	phylink_helper_basex_speed(state);
> >  }
> >  
> >  static int mvneta_mac_link_state(struct net_device *ndev,
> > @@ -3389,7 +3401,9 @@ static int mvneta_mac_link_state(struct net_device *ndev,
> >  	gmac_stat = mvreg_read(pp, MVNETA_GMAC_STATUS);
> >  
> >  	if (gmac_stat & MVNETA_GMAC_SPEED_1000)
> > -		state->speed = SPEED_1000;
> > +		state->speed =
> > +			state->interface == PHY_INTERFACE_MODE_2500BASEX ?
> > +			SPEED_2500 : SPEED_1000;
> >  	else if (gmac_stat & MVNETA_GMAC_SPEED_100)
> >  		state->speed = SPEED_100;
> >  	else
> > @@ -3504,12 +3518,32 @@ static void mvneta_mac_config(struct net_device *ndev, unsigned int mode,
> >  			    MVNETA_GMAC_FORCE_LINK_DOWN);
> >  	}
> >  
> > +
> >  	/* When at 2.5G, the link partner can send frames with shortened
> >  	 * preambles.
> >  	 */
> >  	if (state->speed == SPEED_2500)
> >  		new_ctrl4 |= MVNETA_GMAC4_SHORT_PREAMBLE_ENABLE;
> >  
> > +	if (pp->comphy) {
> > +		enum phy_mode mode = PHY_MODE_INVALID;
> > +
> > +		switch (state->interface) {
> > +		case PHY_INTERFACE_MODE_SGMII:
> > +		case PHY_INTERFACE_MODE_1000BASEX:
> > +			mode = PHY_MODE_SGMII;
> > +			break;
> > +		case PHY_INTERFACE_MODE_2500BASEX:
> > +			mode = PHY_MODE_2500SGMII;
> > +			break;
> > +		default:
> > +			break;
> > +		}
> > +
> > +		if (mode != PHY_MODE_INVALID)
> > +			WARN_ON(phy_set_mode(pp->comphy, mode));
> > +	}
> > +
> >  	if (new_ctrl0 != gmac_ctrl0)
> >  		mvreg_write(pp, MVNETA_GMAC_CTRL_0, new_ctrl0);
> >  	if (new_ctrl2 != gmac_ctrl2)
> > @@ -4411,7 +4445,7 @@ static int mvneta_port_power_up(struct mvneta_port *pp, int phy_mode)
> >  	if (phy_mode == PHY_INTERFACE_MODE_QSGMII)
> >  		mvreg_write(pp, MVNETA_SERDES_CFG, MVNETA_QSGMII_SERDES_PROTO);
> >  	else if (phy_mode == PHY_INTERFACE_MODE_SGMII ||
> > -		 phy_mode == PHY_INTERFACE_MODE_1000BASEX)
> > +		 phy_interface_mode_is_8023z(phy_mode))
> >  		mvreg_write(pp, MVNETA_SERDES_CFG, MVNETA_SGMII_SERDES_PROTO);
> >  	else if (!phy_interface_mode_is_rgmii(phy_mode))
> >  		return -EINVAL;
> > @@ -4428,6 +4462,7 @@ static int mvneta_probe(struct platform_device *pdev)
> >  	struct mvneta_port *pp;
> >  	struct net_device *dev;
> >  	struct phylink *phylink;
> > +	struct phy *comphy;
> >  	const char *dt_mac_addr;
> >  	char hw_mac_addr[ETH_ALEN];
> >  	const char *mac_from;
> > @@ -4453,6 +4488,14 @@ static int mvneta_probe(struct platform_device *pdev)
> >  		goto err_free_irq;
> >  	}
> >  
> > +	comphy = devm_of_phy_get(&pdev->dev, dn, NULL);
> > +	if (comphy == ERR_PTR(-EPROBE_DEFER)) {
> > +		err = -EPROBE_DEFER;
> > +		goto err_free_irq;
> > +	} else if (IS_ERR(comphy)) {
> > +		comphy = NULL;
> > +	}
> 
> devm_phy_optional_get can be used here instead.

I don't think that will work with a NULL string.

devm_phy_optional_get() ultimately ends up calling phy_get(), which
in this case would receive a NULL string.  It will pass that NULL
string to of_property_match_string().

of_property_match_string() will try to find the "phy-names" property,
which will not exist, and hence will return -EINVAL.

phy_get() doesn't check for error conditions, but passes this directly
to _of_phy_get() as the index.  _of_phy_get() passes that on to
of_parse_phandle_with_args(), which will fail to find an entry with
cur_index == -EINVAL (since it counts up from zero.)  Hence,
_of_phy_get() will return -ENODEV, thereby causing
devm_phy_optional_get() to return NULL, even if there's a phys=
property present.

of_phy_get() and phy_get() have different behaviours when a NULL string
is passed in - the of_phy_get() family will get the first PHY specified
in the DT phys= property, whereas the phy_get() family of functions
will fail.

Since there is no devm_of_phy_optional_get(), that leads people down
the path of coding that functionality at the callsites, such as in
drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c.

-- 
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