RE: [PATCH net-next v4 RESEND] stmmac: tegra: Add MGBE support

Hi @Florian Fainelli,
Thanks for the review.

-----Original Message-----
From: Florian Fainelli <f.fainelli@gmail.com>
Sent: 27 September 2022 10:53 PM
To: Thierry Reding <redacted>; David S . Miller
[off-list ref]; Eric Dumazet [off-list ref]; Jakub
Kicinski [off-list ref]; Paolo Abeni [off-list ref]; Russell
King [off-list ref]; Andrew Lunn [off-list ref]; Vladimir
Oltean [off-list ref]
Cc: Jonathan Hunter <jonathanh@nvidia.com>; Bhadram Varka
[off-list ref]; linux-tegra@vger.kernel.org;
netdev@vger.kernel.org
Subject: Re: [PATCH net-next v4 RESEND] stmmac: tegra: Add MGBE support

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+Russell, Andrew, Vladimir,

On 9/23/22 04:49, Thierry Reding wrote:

quoted

From: Bhadram Varka <redacted>

Add support for the Multi-Gigabit Ethernet (MGBE/XPCS) IP found on
NVIDIA Tegra234 SoCs.

Signed-off-by: Bhadram Varka <redacted>
Signed-off-by: Thierry Reding <redacted>
---
  drivers/net/ethernet/stmicro/stmmac/Kconfig   |   6 +
  drivers/net/ethernet/stmicro/stmmac/Makefile  |   1 +
  .../net/ethernet/stmicro/stmmac/dwmac-tegra.c | 290
++++++++++++++++++

You should be modeling this as a proper PCS driver and have a 'pcs-handle'
property pointing to it in your Device Tree.

The configuration you are doing here is probably working the first time you
bring-up the network device but I doubt it works across system
suspend/resume states where power to the GMAC and PCS is lost, it also
begs the question of which mediums this was tested with and whether
dynamic switching of speeds and so on is working?
--

For Tegra234, there is UPHY lanes control logic inside XPCS IP which is memory-mapped IP (not part of the MAC IP).
mgbe_uphy_lane_bringup performs UPHY lane bring up here. Here MGBE/XPCS works in XFI mode.

Agree that lane bring down logic is not present interface down/suspend paths. Will update the changes accordingly.
One more thing is that UPHY lane bring should happen only after the line side link is up. This also will make the changes.
Please let me know if I miss anything here.

Thanks,
Bhadram.