netdev - Re: [PATCH net-next] r8169: reset bus if NIC isn't accessible after tx timeout

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Date:   Fri, 13 Jan 2023 07:39:55 -0800
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...emloft.net>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] r8169: reset bus if NIC isn't accessible after
 tx timeout

On Thu, Jan 12, 2023 at 10:32 PM Heiner Kallweit <hkallweit1@...il.com> wrote:
>
> ASPM issues may result in the NIC not being accessible any longer.
> In this case disabling ASPM may not work. Therefore detect this case
> by checking whether register reads return ~0, and try to make the
> NIC accessible again by resetting the secondary bus.
>
> Suggested-by: Alexander Duyck <alexander.duyck@...il.com>
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> ---
>  drivers/net/ethernet/realtek/r8169_main.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> index 49c124d8e..b79ccde70 100644
> --- a/drivers/net/ethernet/realtek/r8169_main.c
> +++ b/drivers/net/ethernet/realtek/r8169_main.c
> @@ -4535,6 +4535,10 @@ static void rtl_task(struct work_struct *work)
>                 goto out_unlock;
>
>         if (test_and_clear_bit(RTL_FLAG_TASK_TX_TIMEOUT, tp->wk.flags)) {
> +               /* if NIC isn't accessible, reset secondary bus to revive it */
> +               if (RTL_R32(tp, TxConfig) == ~0)
> +                       pci_reset_bus(tp->pci_dev);
> +
>                 /* ASPM compatibility issues are a typical reason for tx timeouts */
>                 ret = pci_disable_link_state(tp->pci_dev, PCIE_LINK_STATE_L1 |
>                                                           PCIE_LINK_STATE_L0S);

So this is headed in the right direction, but you should probably have
some exception handling in place for the pci_reset_bus in the event
that it fails. It is possible that the device is just gone and that in
turn is triggering this. If I recall correctly, when the device
doesn't come back the pci_reset_bus should return -ENOTTY. In such a
case you can probably report that the device has failed and wait for
the PCIe subsystem to notice and notify you that the device is gone
and remove it.