Date: Mon, 19 Feb 2024 02:25:19 +0000
From: Wei Fang <wei.fang@....com>
To: John Ernberg <john.ernberg@...ia.se>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
CC: Jonas Blixt <jonas.blixt@...ia.se>, Shenwei Wang <shenwei.wang@....com>,
	Clark Wang <xiaoning.wang@....com>, Andrew Lunn <andrew@...n.ch>, Heiner
 Kallweit <hkallweit1@...il.com>, Russell King <linux@...linux.org.uk>
Subject: RE: Broken networking on iMX8QXP after suspend after upgrading from
 5.10 to 6.1

Hi John,

> -----Original Message-----
> From: John Ernberg <john.ernberg@...ia.se>
> Sent: 2024年2月8日 21:17
> To: netdev@...r.kernel.org
> Cc: Jonas Blixt <jonas.blixt@...ia.se>; Wei Fang <wei.fang@....com>;
> Shenwei Wang <shenwei.wang@....com>; Clark Wang
> <xiaoning.wang@....com>; Andrew Lunn <andrew@...n.ch>; Heiner
> Kallweit <hkallweit1@...il.com>; Russell King <linux@...linux.org.uk>
> Subject: Broken networking on iMX8QXP after suspend after upgrading from
> 5.10 to 6.1
> 
> Hi,
> 
> We just upgraded vendor kernel from 5.10 to 6.1 and ended up with broken
> networking on our board  unless we bring the PHY up before the first
> suspend of the system.
> 
> The link is brought up via external signal, so it is not guaranteed to have been
> UP before the first system suspend.
> 
> We'd like to run the mainline kernel but we're not in a position to do so yet.
> But we hope we can get some advice on this problem anyway.
> 
> We have a permanently powered Microchip LAN8700R (microchip_t1.c)
> connected to an iMX8QXP (fec), to be able to wake the system via network if
> the link is up.
> 
> This setup was working fine in 5.10.
> 
> The offending commit as far as we could bisect it is:
> 557d5dc83f68 ("net: fec: use mac-managed PHY PM") And somewhat:
> fba863b81604 ("net: phy: make PHY PM ops a no-op if MAC driver manages
> PHY PM")
> 
> If the interface has not been brought UP before the system suspends we can
> see this in dmesg:
> 
>      fec 5b040000.ethernet eth0: MDIO read timeout
>      Microchip LAN87xx T1 5b040000.ethernet-1:04: PM:
> dpm_run_callback(): mdio_bus_phy_resume+0x0/0xc8 returns -110
>      Microchip LAN87xx T1 5b040000.ethernet-1:04: PM: failed to resume:
> error -110
> 
> In this state it is impossible to bring the link up before removing all power
> from the board and then plugging it in again, since the PHY is permanently
> powered.
> 
> My understanding here is that since the link has never been UP,
> fec_enet_open() has never executed, therefor mac_managed_pm is not true.
> This in turn makes us take the normal PM flow.
> Likewise in fec_resume() if the interface is not running, the MAC isn't enabled
> because on the iMX8QXP the FEC is powered down in the suspend path but
> never re-initialized and enabled in the resume path, so the MAC is powered
> back up, but still disabled.
> 
> Adding the following seems to fix the issue, but I personally don't like this,
> because we just allow the non-mac_managed_pm flow to run longer by
> enabling the MAC again rather than letting the MAC do the PM as configured
> in fec_enet_open().
> What would be the correct thing to do here?

Sorry for the delayed response.
Have you tried setting mac_management_pm to true after mdiobus registration?
Just like below:

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 47693ba58ea4..449f56eea2e7 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -2401,8 +2401,6 @@ static int fec_enet_mii_probe(struct net_device *ndev)
        fep->link = 0;
        fep->full_duplex = 0;

-       phy_dev->mac_managed_pm = true;
-
        phy_attached_info(phy_dev);

        return 0;
@@ -2415,10 +2413,12 @@ static int fec_enet_mii_init(struct platform_device *pdev)
        struct net_device *ndev = platform_get_drvdata(pdev);
        struct fec_enet_private *fep = netdev_priv(ndev);
        bool suppress_preamble = false;
+       struct phy_device *phydev;
        struct device_node *node;
        int err = -ENXIO;
        u32 mii_speed, holdtime;
        u32 bus_freq;
+       int addr;

        /*
         * The i.MX28 dual fec interfaces are not equal.
@@ -2533,6 +2533,13 @@ static int fec_enet_mii_init(struct platform_device *pdev)
                goto err_out_free_mdiobus;
        of_node_put(node);

+       /* find all the PHY devices on the bus and set mac_managed_pm to true*/
+       for (addr = 0; addr < PHY_MAX_ADDR; addr++) {
+               phydev = mdiobus_get_phy(fep->mii_bus, addr);
+               if (phydev)
+                       phydev->mac_managed_pm = true;
+       }
+
        mii_cnt++;

> 
> --------- >8 ------
>   drivers/net/ethernet/freescale/fec_main.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> b/drivers/net/ethernet/freescale/fec_main.c
> index a9b61fcf9b5c..6be5f3883582 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -4690,6 +4690,8 @@ static int __maybe_unused fec_resume(struct
> device
> *dev)
>                  ret = fec_restore_mii_bus(ndev);
>                  if (ret < 0)
>                          return ret;
> +       } else {
> +               fec_restart(ndev);
>          }
>          rtnl_unlock();
> 
> --
> 
> Thanks! // John Ernberg

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