netdev - Re: [PATCH v1 1/1] net: stmmac: dwmac-tegra: Read iommu stream id from device tree

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Message-ID: <20241119144729.72e048a5.parker@finest.io>
Date: Tue, 19 Nov 2024 14:47:29 -0500
From: Parker Newman <parker@...est.io>
To: Andrew Lunn <andrew@...n.ch>
Cc: Paolo Abeni <pabeni@...hat.com>, Alexandre Torgue
 <alexandre.torgue@...s.st.com>, Jose Abreu <joabreu@...opsys.com>, Andrew
 Lunn <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Maxime
 Coquelin <mcoquelin.stm32@...il.com>, Thierry Reding
 <thierry.reding@...il.com>, Jonathan Hunter <jonathanh@...dia.com>,
 netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
 linux-kernel@...r.kernel.org, Parker Newman <pnewman@...necttech.com>
Subject: Re: [PATCH v1 1/1] net: stmmac: dwmac-tegra: Read iommu stream id
 from device tree

On Tue, 19 Nov 2024 20:18:00 +0100
Andrew Lunn <andrew@...n.ch> wrote:

> > I think there is some confusion here. I will try to summarize:
> > - Ihe iommu is supported by the Tegra SOC.
> > - The way the mgbe driver is written the iommu DT property is REQUIRED.
>
> If it is required, please also include a patch to
> nvidia,tegra234-mgbe.yaml and make iommus required.
>

I will add this when I submit a v2 of the patch.

> > - "iommus" is a SOC DT property and is defined in tegra234.dtsi.
> > - The mgbe device tree nodes in tegra234.dtsi DO have the iommus property.
> > - There are no device tree changes required to to make this patch work.
> > - This patch works fine with existing device trees.
> >
> > I will add the fallback however in case there is changes made to the iommu
> > subsystem in the future.
>
> I would suggest you make iommus a required property and run the tests
> over the existing .dts files.
>
> I looked at the history of tegra234.dtsi. The ethernet nodes were
> added in:
>
> 610cdf3186bc604961bf04851e300deefd318038
> Author: Thierry Reding <treding@...dia.com>
> Date:   Thu Jul 7 09:48:15 2022 +0200
>
>     arm64: tegra: Add MGBE nodes on Tegra234
>
> and the iommus property is present. So the requires is safe.
>
> Please expand the commit message. It is clear from all the questions
> and backwards and forwards, it does not provide enough details.
>

I will add more details when I submit V2.

> I just have one open issue. The code has been like this for over 2
> years. Why has it only now started crashing?
>

It is rare for Nvidia Jetson users to use the mainline kernel. Nvidia
provides a custom kernel package with many out of tree drivers including a
driver for the mgbe controllers.

Also, while the Orin AGX SOC (tegra234) has 4 instances of the mgbe controller,
the Nvidia Orin AGX devkit only uses mgbe0. Connect Tech has carrier boards
that use 2 or more of the mgbe controllers which is why we found the bug.

Thanks,
Parker