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

[Neftin, Sasha]

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@xxxxxxxxxxxxx>
> > > ---
> > >   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