linux-kernel - MDI errors during resume from ACPI S3 (suspend to ram)

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Message-ID: <81004059-6d91-d8be-c80e-70c52359350d@molgen.mpg.de>
Date:   Tue, 6 Aug 2019 17:36:06 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc:     intel-wired-lan@...ts.osuosl.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mario Limonciello <mario.limonciello@...l.com>
Subject: MDI errors during resume from ACPI S3 (suspend to ram)

Dear Linux folks,


Trying to decrease the resume time of Linux 5.3-rc3 on the Dell OptiPlex
5040 with the device below

    $ lspci -nn -s 00:1f.6
    00:1f.6 Ethernet controller [0200]: Intel Corporation Ethernet Connection (2) I219-V [8086:15b8] (rev 31)

pm-graph’s script `sleepgraph.py` shows, that the driver *e1000e* takes
around 400 ms, which is quite a lot. The call graph trace shows that
`e1000e_read_phy_reg_mdic()` is responsible for a lot of those. From
`drivers/net/ethernet/intel/e1000e/phy.c` [1]:

        for (i = 0; i < (E1000_GEN_POLL_TIMEOUT * 3); i++) {
                udelay(50);
                mdic = er32(MDIC);
                if (mdic & E1000_MDIC_READY)
                        break;
        }
        if (!(mdic & E1000_MDIC_READY)) {
                e_dbg("MDI Read did not complete\n");
                return -E1000_ERR_PHY;
        }
        if (mdic & E1000_MDIC_ERROR) {
                e_dbg("MDI Error\n");
                return -E1000_ERR_PHY;
        }

Unfortunately, errors are not logged if dynamic debug is disabled,
so rebuilding the Linux kernel with `CONFIG_DYNAMIC_DEBUG`, and

    echo "file drivers/net/ethernet/* +p" | sudo tee /sys/kernel/debug/dynamic_debug/control

I got the messages below.

    [ 4159.204192] e1000e 0000:00:1f.6 net00: MDI Error
    [ 4160.267950] e1000e 0000:00:1f.6 net00: MDI Write did not complete
    [ 4160.359855] e1000e 0000:00:1f.6 net00: MDI Error

Can you please shed a little more light into these errors? Please
find the full log attached.


Kind regards,

Paul


[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/ethernet/intel/e1000e/phy.c#n206

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