netdev - [PATCH net-next v2 2/7] net: phy: add rxc_always_on flag to phylink

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Message-Id: <20240130-rxc_bugfix-v2-2-5e6c3168e5f0@bootlin.com>
Date: Tue, 30 Jan 2024 10:28:37 +0100
From: Romain Gantois <romain.gantois@...tlin.com>
To: Russell King <linux@...linux.org.uk>, Andrew Lunn <andrew@...n.ch>, 
 Heiner Kallweit <hkallweit1@...il.com>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Alexandre Torgue <alexandre.torgue@...s.st.com>, 
 Jose Abreu <joabreu@...opsys.com>, 
 Maxime Coquelin <mcoquelin.stm32@...il.com>, 
 Clément Léger <clement.leger@...tlin.com>
Cc: Maxime Chevallier <maxime.chevallier@...tlin.com>, 
 Miquel Raynal <miquel.raynal@...tlin.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, netdev@...r.kernel.org, 
 linux-stm32@...md-mailman.stormreply.com, 
 linux-arm-kernel@...ts.infradead.org, linux-renesas-soc@...r.kernel.org, 
 Romain Gantois <romain.gantois@...tlin.com>
Subject: [PATCH net-next v2 2/7] net: phy: add rxc_always_on flag to
 phylink_pcs

Some MAC drivers (e.g. stmmac) require a continuous receive clock signal to
be generated by a PCS that is handled by a standalone PCS driver.

Such a PCS driver does not have access to a PHY device, thus cannot check
the PHY_F_RXC_ALWAYS_ON flag. They cannot check max_requires_rxc in the
phylink config either, since it is a private member. Therefore, a new flag
is needed to signal to the PCS that it should keep the RX clock signal up
at all times.

Suggested-by: Russell King <linux@...linux.org.uk>
Signed-off-by: Romain Gantois <romain.gantois@...tlin.com>
---
 drivers/net/phy/phylink.c | 14 ++++++++++++++
 include/linux/phylink.h   | 11 +++++++++++
 2 files changed, 25 insertions(+)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 851049096488..6fcc0a8ba122 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -1042,6 +1042,20 @@ static void phylink_pcs_poll_start(struct phylink *pl)
 		mod_timer(&pl->link_poll, jiffies + HZ);
 }

+int phylink_pcs_pre_init(struct phylink *pl, struct phylink_pcs *pcs)
+{
+	int ret = 0;
+
+	/* Signal to PCS driver that MAC requires RX clock for init */
+	if (pl->config->mac_requires_rxc)
+		pcs->rxc_always_on = true;
+
+	if (pcs->ops->pcs_pre_init)
+		ret = pcs->ops->pcs_pre_init(pcs, pl->link_config.interface);
+
+	return ret;
+}
+
 static void phylink_mac_config(struct phylink *pl,
 			       const struct phylink_link_state *state)
 {
diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index fcee99632964..71e970271fd3 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -396,6 +396,10 @@ struct phylink_pcs_ops;
  * @phylink: pointer to &struct phylink_config
  * @neg_mode: provide PCS neg mode via "mode" argument
  * @poll: poll the PCS for link changes
+ * @rxc_always_on: The MAC driver requires the reference clock
+ *                 to always be on. Standalone PCS drivers which
+ *                 do not have access to a PHY device can check
+ *                 this instead of PHY_F_RXC_ALWAYS_ON.
  *
  * This structure is designed to be embedded within the PCS private data,
  * and will be passed between phylink and the PCS.
@@ -408,6 +412,7 @@ struct phylink_pcs {
 	struct phylink *phylink;
 	bool neg_mode;
 	bool poll;
+	bool rxc_always_on;
 };

 /**
@@ -422,6 +427,8 @@ struct phylink_pcs {
  * @pcs_an_restart: restart 802.3z BaseX autonegotiation.
  * @pcs_link_up: program the PCS for the resolved link configuration
  *               (where necessary).
+ * @pcs_pre_init: configure PCS components necessary for MAC hardware
+ *                initialization e.g. RX clock for stmmac.
  */
 struct phylink_pcs_ops {
 	int (*pcs_validate)(struct phylink_pcs *pcs, unsigned long *supported,
@@ -441,6 +448,8 @@ struct phylink_pcs_ops {
 	void (*pcs_an_restart)(struct phylink_pcs *pcs);
 	void (*pcs_link_up)(struct phylink_pcs *pcs, unsigned int neg_mode,
 			    phy_interface_t interface, int speed, int duplex);
+	int (*pcs_pre_init)(struct phylink_pcs *pcs,
+			    phy_interface_t interface);
 };

 #if 0 /* For kernel-doc purposes only. */
@@ -568,6 +577,8 @@ void phylink_disconnect_phy(struct phylink *);
 void phylink_mac_change(struct phylink *, bool up);
 void phylink_pcs_change(struct phylink_pcs *, bool up);

+int phylink_pcs_pre_init(struct phylink *pl, struct phylink_pcs *pcs);
+
 void phylink_start(struct phylink *);
 void phylink_stop(struct phylink *);

-- 
2.43.0