[PATCH v4 net-next 3/9] net: phylink: add support for polling MAC PCS

[Vladimir Oltean <olteanv@gmail.com>]

From: Vladimir Oltean <vladimir.oltean@nxp.com>

Some MAC PCS blocks are unable to provide interrupts when their status
changes. As we already have support in phylink for polling status, use
this to provide a hook for MACs to enable polling mode.

The patch idea was picked up from Russell King's suggestion on the macb
phylink patch thread here [0] but the implementation was changed.
Instead of introducing a new phylink_start_poll() function, which would
make the implementation cumbersome for common PHYLINK implementations
for multiple types of devices, like DSA, just add a boolean property to
the phylink_config structure, which is just as backwards-compatible.

https://lkml.org/lkml/2019/12/16/603

Suggested-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
Changes in v4:
- None.

 Documentation/networking/sfp-phylink.rst | 3 ++-
 drivers/net/phy/phylink.c                | 3 ++-
 include/linux/phylink.h                  | 2 ++
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Documentation/networking/sfp-phylink.rst b/Documentation/networking/sfp-phylink.rst
index a5e00a159d21..d753a309f9d1 100644
--- a/Documentation/networking/sfp-phylink.rst
+++ b/Documentation/networking/sfp-phylink.rst
@@ -251,7 +251,8 @@ this documentation.
 	phylink_mac_change(priv->phylink, link_is_up);
 
     where ``link_is_up`` is true if the link is currently up or false
-    otherwise.
+    otherwise. If a MAC is unable to provide these interrupts, then
+    it should set ``priv->phylink_config.pcs_poll = true;`` in step 9.
 
 11. Verify that the driver does not call::
 
diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index c19cbcf183e6..73a01ea5fc55 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -1021,7 +1021,8 @@ void phylink_start(struct phylink *pl)
 		if (irq <= 0)
 			mod_timer(&pl->link_poll, jiffies + HZ);
 	}
-	if (pl->cfg_link_an_mode == MLO_AN_FIXED && pl->get_fixed_state)
+	if ((pl->cfg_link_an_mode == MLO_AN_FIXED && pl->get_fixed_state) ||
+	    pl->config->pcs_poll)
 		mod_timer(&pl->link_poll, jiffies + HZ);
 	if (pl->phydev)
 		phy_start(pl->phydev);
diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index fed5488e3c75..523209e70947 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -63,10 +63,12 @@ enum phylink_op_type {
  * struct phylink_config - PHYLINK configuration structure
  * @dev: a pointer to a struct device associated with the MAC
  * @type: operation type of PHYLINK instance
+ * @pcs_poll: MAC PCS cannot provide link change interrupt
  */
 struct phylink_config {
 	struct device *dev;
 	enum phylink_op_type type;
+	bool pcs_poll;
 };
 
 /**
-- 
2.17.1