linux-kernel - [PATCH net v4 0/1] net: fec: Fix to suspend / resume with mac_managed

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Date: Thu, 28 Mar 2024 15:59:29 +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>,
	"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>, "imx@...ts.linux.dev"
	<imx@...ts.linux.dev>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Florian
 Fainelli" <f.fainelli@...il.com>, Russell King <linux@...linux.org.uk>,
	"Maxime Chevallier" <maxime.chevallier@...tlin.com>, John Ernberg
	<john.ernberg@...ia.se>
Subject: [PATCH net v4 0/1] net: fec: Fix 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/

v4:
 - Adjustments to commit message in patch 1
 - Drop patch 2 after discussion in v3.

v3: https://lore.kernel.org/netdev/20240306133734.4144808-1-john.ernberg@actia.se/
 - 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/

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

 drivers/net/ethernet/freescale/fec_main.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

-- 
2.44.0