netdev - Re: [Intel-wired-lan] [PATCH 2/2] igc: wait for the MAC copy when enabled MAC passthrough

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Message-ID: <f9f9408e-9ba3-7ed9-acc2-1c71913b04f0@intel.com>
Date:   Mon, 5 Jul 2021 14:54:39 +0300
From:   "Neftin, Sasha" <sasha.neftin@...el.com>
To:     Aaron Ma <aaron.ma@...onical.com>, jesse.brandeburg@...el.com,
        anthony.l.nguyen@...el.com, davem@...emloft.net, kuba@...nel.org,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Edri, Michael" <michael.edri@...el.com>,
        "Ruinskiy, Dima" <dima.ruinskiy@...el.com>,
        "Shalev, Avi" <avi.shalev@...el.com>,
        "Ruinskiy, Dima" <dima.ruinskiy@...el.com>,
        "Neftin, Sasha" <sasha.neftin@...el.com>
Subject: Re: [Intel-wired-lan] [PATCH 2/2] igc: wait for the MAC copy when
 enabled MAC passthrough

On 7/5/2021 10:38, Aaron Ma wrote:
> 
> 
> On 7/4/21 1:36 PM, Neftin, Sasha wrote:
>> On 7/2/2021 07:51, Aaron Ma wrote:
>>> Such as dock hot plug event when runtime, for hardware implementation,
>>> the MAC copy takes less than one second when BIOS enabled MAC 
>>> passthrough.
>>> After test on Lenovo TBT4 dock, 600ms is enough to update the
>>> MAC address.
>>> Otherwise ethernet fails to work.
>>>
>>> Signed-off-by: Aaron Ma <aaron.ma@...onical.com>
>>> ---
>>>   drivers/net/ethernet/intel/igc/igc_main.c | 3 +++
>>>   1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c 
>>> b/drivers/net/ethernet/intel/igc/igc_main.c
>>> index 606b72cb6193..c8bc5f089255 100644
>>> --- a/drivers/net/ethernet/intel/igc/igc_main.c
>>> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
>>> @@ -5468,6 +5468,9 @@ static int igc_probe(struct pci_dev *pdev,
>>>       memcpy(&hw->mac.ops, ei->mac_ops, sizeof(hw->mac.ops));
>>>       memcpy(&hw->phy.ops, ei->phy_ops, sizeof(hw->phy.ops));
>>> +    if (pci_is_thunderbolt_attached(pdev) > +        msleep(600);
>> I believe it is a bit fragile. I would recommend here look for another 
>> indication instead of delay. Can we poll for a 'pci_channel_io_normal' 
>> state? (igc->pdev->error_state == pci_channel_io_normal)
> 
> Hi sasha,
> In this situation, the error_state is always pci_channel_io_normal.
Ok.
> The delay is necessary.
> 
> Refer to "627239-Intel® Ethernet Controller 
> I225-MAC-Address-Passthrough-rev1.2"
> section "3.5
>   Timing Considerations":
Hello Aaron, Thanks to point me on this document. I see... This is 
recommendation for Windows driver. Anyway, "delay" approach is 
error-prone. We need rather ask for MNG FW confirmation (message) that 
MAC address is copied.
Can we call (in case we know that MNG FW copied MAC address):
igc_rar_set (method from igc_mac.c), update the mac.addr and then 
perform": memcpy(netdev->dev_addr, hw->mac.addr, netdev->addr_len);?

> "For hardware implementation,
> 
> when the operating system is already running, the MAC copy must happen 
> not more than one
> 
> second after TBT link is established.
> the I225 Windows driver prevents the operating
> 
> system from detecting the I225 for one second. This allows enough time 
> for hardware to update the
> 
> MAC address."
> 
> Thanks sasha,
> Aaron
> 
>>> +
>>>       /* Initialize skew-specific constants */
>>>       err = ei->get_invariants(hw);
>>>       if (err)
>>>
>> Thanks Aaron,
>> sasha
Sasha