linux-kernel - [PATCH net v3 0/3] net: phy: smsc: use IRQ + relaxed polling to fix missed link-up

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Message-Id: <20250711094909.1086417-1-o.rempel@pengutronix.de>
Date: Fri, 11 Jul 2025 11:49:06 +0200
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: 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>
Cc: Oleksij Rempel <o.rempel@...gutronix.de>,
	kernel@...gutronix.de,
	linux-kernel@...r.kernel.org,
	Russell King <linux@...linux.org.uk>,
	netdev@...r.kernel.org,
	Andre Edich <andre.edich@...rochip.com>,
	Lukas Wunner <lukas@...ner.de>
Subject: [PATCH net v3 0/3] net: phy: smsc: use IRQ + relaxed polling to fix missed link-up

This series makes the SMSC LAN8700 (as used in LAN9512 and similar USB
adapters) reliable again in configurations where it is forced to 10 Mb/s
and the link partner still advertises autonegotiation.

In this scenario, the PHY may miss the final link-up interrupt, causing
the network interface to remain down even though a valid link is
present.

To address this:

Patch 1 – phylib: Enable polling if the driver implements
get_next_update_time(). This ensures the state machine is active even
without update_stats().

Patch 2 – phylib: Allow drivers to return PHY_STATE_IRQ to explicitly
disable polling.

Patch 3 – smsc: Implement get_next_update_time() with adaptive 1 Hz
polling for up to 30 seconds after the last interrupt in the affected
10M autoneg-off mode.  All other configurations rely on IRQs only.

Testing:

The LAN9512 (LAN8700 core) was tested against an Intel I350 NIC using
baseline, parallel-detection, and advertisement test suites. All
relevant tests passed.

Changes in v3:
- handle conflicting configuration if update_stats are supported

Changes in v2:
- Introduced explicit disable polling via PHY_STATE_IRQ
- Changed the workaround logic to apply 1 Hz polling only for 30 seconds
  after the last IRQ
- Dropped relaxed 30s polling while link is up
- Reworded commit messages and comments to reflect updated logic
- Split core changes into two separate patches for clarity

Thanks,
Oleksij Rempel

Oleksij Rempel (3):
  net: phy: enable polling when driver implements get_next_update_time
  net: phy: allow drivers to disable polling via get_next_update_time()
  net: phy: smsc: recover missed link-up IRQs on LAN8700 with adaptive
    polling

 drivers/net/phy/phy.c  | 27 ++++++++++++++++++++-------
 drivers/net/phy/smsc.c | 40 ++++++++++++++++++++++++++++++++++++++++
 include/linux/phy.h    | 17 +++++++++++++++--
 3 files changed, 75 insertions(+), 9 deletions(-)

--
2.39.5