Subject: Re: [PATCH 2/3] of_mdio: add new DT property 'autoneg' for fixed-link

From: Florian Fainelli <[email-masked]>
Date: Fri, 10 Jul 2015 11:37:45 -0700

On 10/07/15 09:43, Stas Sergeev wrote:
> 
> Currently for fixed-link the MAC driver decides whether to use the
> link status auto-negotiation or not.
> Unfortunately the auto-negotiation may not work when expected by
> the MAC driver. Sebastien Rannou explains:
> << Yes, I confirm that my HW does not generate an in-band status. AFAIK, it's
> a PHY that aggregates 4xSGMIIs to 1xQSGMII ; the MAC side of the PHY (with
> inband status) is connected to the switch through QSGMII, and in this context
> we are on the media side of the PHY. >>
> https://lkml.org/lkml/2015/7/10/206
> 
> This patch introduces the new boolean property 'autoneg' that allows
> the user to request the auto-negotiation explicitly.

The implementation looks better, but the name might still be slightly
controversial. I would go with "use-in-band-status" which is more
strictly defined than "autoneg" which could mean anything and everything.

What do you think?

> 
> Signed-off-by: Stas Sergeev <[email-masked]>
> 
> CC: Rob Herring <[email-masked]>
> CC: Pawel Moll <[email-masked]>
> CC: Mark Rutland <[email-masked]>
> CC: Ian Campbell <[email-masked]>
> CC: Kumar Gala <[email-masked]>
> CC: Florian Fainelli <[email-masked]>
> CC: Grant Likely <[email-masked]>
> CC: [email-masked]
> CC: [email-masked]
> CC: [email-masked]
> ---
>  .../devicetree/bindings/net/fixed-link.txt         |  6 +++++-
>  drivers/of/of_mdio.c                               | 23 ++++++++++++++++++++--
>  include/linux/of_mdio.h                            |  5 +++++
>  3 files changed, 31 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/net/fixed-link.txt b/Documentation/devicetree/bindings/net/fixed-link.txt
> index 82bf7e0..e2959a8 100644
> --- a/Documentation/devicetree/bindings/net/fixed-link.txt
> +++ b/Documentation/devicetree/bindings/net/fixed-link.txt
> @@ -9,8 +9,12 @@ Such a fixed link situation is described by creating a 'fixed-link'
>  sub-node of the Ethernet MAC device node, with the following
>  properties:
> 
> +* 'autoneg' (boolean, optional), to enable the auto-negotiation of link
> +  state. Auto-negotiation is MII protocol, HW and driver-specific and is
> +  not supported in many cases, so use it only when you know what you do.
>  * 'speed' (integer, mandatory), to indicate the link speed. Accepted
> -  values are 10, 100 and 1000
> +  values are 10, 100 and 1000. If the auto-negotiation is enabled,
> +  'speed' may not be set. It will then be auto-negotiated, if possible.
>  * 'full-duplex' (boolean, optional), to indicate that full duplex is
>    used. When absent, half duplex is assumed.
>  * 'pause' (boolean, optional), to indicate that pause should be
> diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
> index 1bd4305..12b2ede 100644
> --- a/drivers/of/of_mdio.c
> +++ b/drivers/of/of_mdio.c
> @@ -280,6 +280,22 @@ bool of_phy_is_fixed_link(struct device_node *np)
>  }
>  EXPORT_SYMBOL(of_phy_is_fixed_link);
> 
> +bool of_phy_is_autoneg_link(struct device_node *np)
> +{
> +	struct device_node *dn;
> +	bool ret;
> +
> +	dn = of_get_child_by_name(np, "fixed-link");
> +	if (!dn)
> +		return false;
> +
> +	ret = of_property_read_bool(dn, "autoneg");
> +
> +	of_node_put(dn);
> +	return ret;
> +}
> +EXPORT_SYMBOL(of_phy_is_autoneg_link);
> +
>  int of_phy_register_fixed_link(struct device_node *np)
>  {
>  	struct fixed_phy_status status = {};
> @@ -291,10 +307,13 @@ int of_phy_register_fixed_link(struct device_node *np)
>  	/* New binding */
>  	fixed_link_node = of_get_child_by_name(np, "fixed-link");
>  	if (fixed_link_node) {
> -		status.link = 1;
> +		bool autoneg = of_property_read_bool(fixed_link_node,
> +						     "autoneg");
> +		status.link = !autoneg;
>  		status.duplex = of_property_read_bool(fixed_link_node,
>  						      "full-duplex");
> -		if (of_property_read_u32(fixed_link_node, "speed", &status.speed))
> +		if (of_property_read_u32(fixed_link_node, "speed",
> +					 &status.speed) != 0 && !autoneg)
>  			return -EINVAL;
>  		status.pause = of_property_read_bool(fixed_link_node, "pause");
>  		status.asym_pause = of_property_read_bool(fixed_link_node,
> diff --git a/include/linux/of_mdio.h b/include/linux/of_mdio.h
> index d449018..647f348 100644
> --- a/include/linux/of_mdio.h
> +++ b/include/linux/of_mdio.h
> @@ -65,6 +65,7 @@ static inline struct mii_bus *of_mdio_find_bus(struct device_node *mdio_np)
>  #if defined(CONFIG_OF) && defined(CONFIG_FIXED_PHY)
>  extern int of_phy_register_fixed_link(struct device_node *np);
>  extern bool of_phy_is_fixed_link(struct device_node *np);
> +extern bool of_phy_is_autoneg_link(struct device_node *np);
>  #else
>  static inline int of_phy_register_fixed_link(struct device_node *np)
>  {
> @@ -74,6 +75,10 @@ static inline bool of_phy_is_fixed_link(struct device_node *np)
>  {
>  	return false;
>  }
> +static inline bool of_phy_is_autoneg_link(struct device_node *np)
> +{
> +	return false;
> +}
>  #endif
> 
> 

-- 
Florian