linux-kernel - [PATCH net v3 0/2] net: fec: Fixes to suspend / resume with mac_managed

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Date: Wed, 6 Mar 2024 13:37:45 +0000
From: John Ernberg <john.ernberg@...ia.se>
To: Wei Fang <wei.fang@....com>
CC: Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>,
	NXP Linux Team <linux-imx@....com>, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, "Paolo
 Abeni" <pabeni@...hat.com>, Heiner Kallweit <hkallweit1@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, John Ernberg
	<john.ernberg@...ia.se>
Subject: [PATCH net v3 0/2] net: fec: Fixes to suspend / resume with
 mac_managed_pm

Since the introduction of mac_managed_pm in the FEC driver there were some
discrepancies regarding power management of the PHY.

This failed on our board that has a permanently powered Microchip LAN8700R
attached to the FEC. Although the root cause of the failure can be traced
back to f166f890c8f0 ("net: ethernet: fec: Replace interrupt driven MDIO
with polled IO") and probably even before that, we only started noticing
the problem going from 5.10 to 6.1.

Since 557d5dc83f68 ("net: fec: use mac-managed PHY PM") is actually a fix
to most of the power management sequencing problems that came with power
managing the MDIO bus which for the FEC meant adding a race with FEC
resume (and phy_start() if netif was running) and PHY resume.

That it worked before for us was probably just luck...

Thanks to Wei's response to my report at [1] I was able to pick up his
patch and start honing in on the remaining missing details.

[1]: https://lore.kernel.org/netdev/1f45bdbe-eab1-4e59-8f24-add177590d27@actia.se/

v3:
 - Implement feedback from Wei Fang for patch 2
 - Fixes tag in patch 2 dropped, should it be delayed for net-next now?

v2: https://lore.kernel.org/netdev/20240229105256.2903095-1-john.ernberg@actia.se/
 - Completely different approach that should be much more correct
   (Wei Fang, Jakub Kicinski)
 - Re-target to net tree, because I have fixes tags now

v1: https://lore.kernel.org/netdev/20240212105010.2258421-1-john.ernberg@actia.se/

John Ernberg (1):
  net: fec: Suspend the PHY on probe

Wei Fang (1):
  net: fec: Set mac_managed_pm during probe

 drivers/net/ethernet/freescale/fec_main.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

-- 
2.43.0