[net,v5,1/3] net: phylink: add phylink_expects_phy() method

Commit Message

Sit, Michael Wei Hong March 30, 2023, 9:14 a.m. UTC

Provide phylink_expects_phy() to allow MAC drivers to check if it
is expecting a PHY to attach to. Since fixed-linked setups do not
need to attach to a PHY.

Provides a boolean value as to if the MAC should expect a PHY.
Returns true if a PHY is expected.

Reviewed-by: Russell King (Oracle) <[e-mail]>
Signed-off-by: Michael Sit Wei Hong <[e-mail]>
---
 drivers/net/phy/phylink.c | 19 +++++++++++++++++++
 include/linux/phylink.h   |  1 +
 2 files changed, 20 insertions(+)

Comments

Sit, Michael Wei Hong April 12, 2023, 6:58 a.m. UTC | #1

> -----Original Message-----
> From: Maxime Chevallier <[e-mail]>
> Sent: Wednesday, April 12, 2023 4:38 PM
> To: Sit, Michael Wei Hong <[e-mail]>
> Cc: Giuseppe Cavallaro <[e-mail]>; Alexandre
> Torgue <[e-mail]>; Jose Abreu
> <[e-mail]>; David S . Miller <[e-mail]>;
> Eric Dumazet <[e-mail]>; Jakub Kicinski
> <[e-mail]>; Paolo Abeni <[e-mail]>; Maxime
> Coquelin <[e-mail]>; Ong, Boon Leong
> <[e-mail]>; [e-mail]; linux-
> [e-mail]; linux-arm-
> [e-mail]; [e-mail];
> [e-mail]; [e-mail]; [e-mail];
> Looi, Hong Aun <[e-mail]>; Voon, Weifeng
> <[e-mail]>; Lai, Peter Jun Ann
> <[e-mail]>; [e-mail]
> Subject: Re: [PATCH net v5 1/3] net: phylink: add
> phylink_expects_phy() method
> 
> Hello everyone,
> 
> On Thu, 30 Mar 2023 17:14:02 +0800
> Michael Sit Wei Hong <[e-mail]> wrote:
> 
> > Provide phylink_expects_phy() to allow MAC drivers to check if it is
> > expecting a PHY to attach to. Since fixed-linked setups do not need
> to
> > attach to a PHY.
> >
> > Provides a boolean value as to if the MAC should expect a PHY.
> > Returns true if a PHY is expected.
> 
> I'm currently working on the TSE rework for dwmac_socfpga, and I
> noticed one regression since this patch, when using an SFP, see
> details below :
> 
> > Reviewed-by: Russell King (Oracle) <[e-mail]>
> > Signed-off-by: Michael Sit Wei Hong
> <[e-mail]>
> > ---
> >  drivers/net/phy/phylink.c | 19 +++++++++++++++++++
> >  include/linux/phylink.h   |  1 +
> >  2 files changed, 20 insertions(+)
> >
> > diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> > index 1a2f074685fa..30c166b33468 100644
> > --- a/drivers/net/phy/phylink.c
> > +++ b/drivers/net/phy/phylink.c
> > @@ -1586,6 +1586,25 @@ void phylink_destroy(struct phylink
> *pl)  }
> > EXPORT_SYMBOL_GPL(phylink_destroy);
> >
> > +/**
> > + * phylink_expects_phy() - Determine if phylink expects a phy to
> be
> > attached
> > + * @pl: a pointer to a &struct phylink returned from
> phylink_create()
> > + *
> > + * When using fixed-link mode, or in-band mode with 1000base-X
> or
> > 2500base-X,
> > + * no PHY is needed.
> > + *
> > + * Returns true if phylink will be expecting a PHY.
> > + */
> > +bool phylink_expects_phy(struct phylink *pl) {
> > +	if (pl->cfg_link_an_mode == MLO_AN_FIXED ||
> > +	    (pl->cfg_link_an_mode == MLO_AN_INBAND &&
> > +	     phy_interface_mode_is_8023z(pl->link_config.interface)))
> 
> From the discussion, at one point Russell mentionned [1] :
> "If there's a sfp bus, then we don't expect a PHY from the MAC
> driver (as there can only be one PHY attached), and as
> phylink_expects_phy() is for the MAC driver to use, we should be
> returning false if
> pl->sfp_bus != NULL."
> 
> This makes sense and indeed adding the relevant check solves the
> issue.
> 
> Am I correct in assuming this was an unintentional omission from
> this patch, or was the pl->sfp_bus check dropped on purpose ?
> 
> > +		return false;
> > +	return true;
> > +}
> > +EXPORT_SYMBOL_GPL(phylink_expects_phy);
> 
> Thanks,
> 
> Maxime
> 

Russell also did mention:
" The reason for the extra "&& !pl->sfp_bus" in phylink_attach_phy()
is to allow SFPs to connect to the MAC using inband mode with
1000base-X and 2500base-X interface modes. These are not for the
MAC-side of things though."

So I thought that the check can be dropped. I do not have any SFP hardware
to test, if adding the check make sense, you can send us a patch so we can
test it out.
> [1] :
> https://lore.kernel.org/netdev/[e-mail].o
> rg.uk/

Maxime Chevallier April 12, 2023, 8:38 a.m. UTC | #2

Hello everyone,

On Thu, 30 Mar 2023 17:14:02 +0800
Michael Sit Wei Hong <[e-mail]> wrote:

> Provide phylink_expects_phy() to allow MAC drivers to check if it
> is expecting a PHY to attach to. Since fixed-linked setups do not
> need to attach to a PHY.
> 
> Provides a boolean value as to if the MAC should expect a PHY.
> Returns true if a PHY is expected.

I'm currently working on the TSE rework for dwmac_socfpga, and I
noticed one regression since this patch, when using an SFP, see details
below :

> Reviewed-by: Russell King (Oracle) <[e-mail]>
> Signed-off-by: Michael Sit Wei Hong <[e-mail]>
> ---
>  drivers/net/phy/phylink.c | 19 +++++++++++++++++++
>  include/linux/phylink.h   |  1 +
>  2 files changed, 20 insertions(+)
> 
> diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> index 1a2f074685fa..30c166b33468 100644
> --- a/drivers/net/phy/phylink.c
> +++ b/drivers/net/phy/phylink.c
> @@ -1586,6 +1586,25 @@ void phylink_destroy(struct phylink *pl)
>  }
>  EXPORT_SYMBOL_GPL(phylink_destroy);
>  
> +/**
> + * phylink_expects_phy() - Determine if phylink expects a phy to be
> attached
> + * @pl: a pointer to a &struct phylink returned from phylink_create()
> + *
> + * When using fixed-link mode, or in-band mode with 1000base-X or
> 2500base-X,
> + * no PHY is needed.
> + *
> + * Returns true if phylink will be expecting a PHY.
> + */
> +bool phylink_expects_phy(struct phylink *pl)
> +{
> +	if (pl->cfg_link_an_mode == MLO_AN_FIXED ||
> +	    (pl->cfg_link_an_mode == MLO_AN_INBAND &&
> +	     phy_interface_mode_is_8023z(pl->link_config.interface)))

From the discussion, at one point Russell mentionned [1] :
"If there's a sfp bus, then we don't expect a PHY from the MAC driver
(as there can only be one PHY attached), and as phylink_expects_phy()
is for the MAC driver to use, we should be returning false if
pl->sfp_bus != NULL."

This makes sense and indeed adding the relevant check solves the issue.

Am I correct in assuming this was an unintentional omission from this
patch, or was the pl->sfp_bus check dropped on purpose ?

> +		return false;
> +	return true;
> +}
> +EXPORT_SYMBOL_GPL(phylink_expects_phy);

Thanks,

Maxime

[1] :
https://lore.kernel.org/netdev/[e-mail]/

Patch

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 1a2f074685fa..30c166b33468 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -1586,6 +1586,25 @@  void phylink_destroy(struct phylink *pl)
 }
 EXPORT_SYMBOL_GPL(phylink_destroy);
 
+/**
+ * phylink_expects_phy() - Determine if phylink expects a phy to be attached
+ * @pl: a pointer to a &struct phylink returned from phylink_create()
+ *
+ * When using fixed-link mode, or in-band mode with 1000base-X or 2500base-X,
+ * no PHY is needed.
+ *
+ * Returns true if phylink will be expecting a PHY.
+ */
+bool phylink_expects_phy(struct phylink *pl)
+{
+	if (pl->cfg_link_an_mode == MLO_AN_FIXED ||
+	    (pl->cfg_link_an_mode == MLO_AN_INBAND &&
+	     phy_interface_mode_is_8023z(pl->link_config.interface)))
+		return false;
+	return true;
+}
+EXPORT_SYMBOL_GPL(phylink_expects_phy);
+
 static void phylink_phy_change(struct phy_device *phydev, bool up)
 {
 	struct phylink *pl = phydev->phylink;
diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index c492c26202b5..637698ed5cb6 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -574,6 +574,7 @@  struct phylink *phylink_create(struct phylink_config *, struct fwnode_handle *,
 			       phy_interface_t iface,
 			       const struct phylink_mac_ops *mac_ops);
 void phylink_destroy(struct phylink *);
+bool phylink_expects_phy(struct phylink *pl);
 
 int phylink_connect_phy(struct phylink *, struct phy_device *);
 int phylink_of_phy_connect(struct phylink *, struct device_node *, u32 flags);