linux-kernel - Re: [PATCH v2 0/4] PCI: rockchip: 5.0 GT/s speed may be dangerous

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Message-ID: <e5d5c0dc-81d6-ae0e-7552-c2e4fb39bb0a@manjaro.org>
Date: Tue, 18 Nov 2025 07:45:45 +0100
From: "Dragan Simic" <dsimic@...jaro.org>
To: "Geraldo Nascimento" <geraldogabriel@...il.com>
Cc: "Shawn Lin" <shawn.lin@...k-chips.com>, "Lorenzo Pieralisi" <lpieralisi@...nel.org>, Krzysztof Wilczyński <kwilczynski@...nel.org>, "Manivannan Sadhasivam" <mani@...nel.org>, "Rob Herring" <robh@...nel.org>, "Bjorn Helgaas" <bhelgaas@...gle.com>, "Heiko Stuebner" <heiko@...ech.de>, "Krzysztof Kozlowski" <krzk+dt@...nel.org>, "Conor Dooley" <conor+dt@...nel.org>, "Johan Jonker" <jbx6244@...il.com>, linux-rockchip@...ts.infradead.org, linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 0/4] PCI: rockchip: 5.0 GT/s speed may be dangerous

Hello Geraldo,

Thanks a lot for the v2!  Please, see some comments below.

On Monday, November 17, 2025 22:46 CET, Geraldo Nascimento <geraldogabriel@...il.com> wrote:
> Dragan Simic already had warned me of potential issues with 5.0 GT/s
> speed operation in Rockchip PCIe. However, in recent interactions
> with Shawn Lin from Rockchip it came to my attention there's grave
> danger in the unknown errata regarding 5.0 GT/s operational speed
> of their PCIe core. Even if the odds are low, to contain any damage,
> let's cover the remaining corner-cases where the default would lead
> to 5.0 GT/s operation as well as add a comment to Root Complex driver
> core, documenting this danger. Furthermore, remove redundant
> declaration of max-link-speed from rk3399-nanopi-r4s.dtsi
> 
> Signed-off-by: Geraldo Nascimento <geraldogabriel@...il.com>

As a note, Signed-off-by tags are redundant in cover letters, because
there's no source code in them that can actually be signed off.

> Changes in v2:
> - hard limit to 2.5 GT/s, not just warn
> - add Reported-by: and Reviewed-by: Dragan Simic
> - remove redundant declaration of max-link-speed from helios64 dts
> - fix Link: of helios64 patch
> - simplify RC mode comment
> - Link to v1: https://lore.kernel.org/all/aRhR79u5BPtRRFw3@geday/

Technically, you shouldn't have included my Reviewed-by tags in some
of the patches in the v2 of this series, because the patches were
either modified significantly since I gave my Reviewed-by for them
in the v1, or they were actually introduced in the v2.

However, I checked all four patches in the v2 again and everything
is still fine, so just to make sure, please feel free to include for
the entire series:

Reviewed-by: Dragan Simic <dsimic@...jaro.org>

> Geraldo Nascimento (4):
>   PCI: rockchip: limit RK3399 to 2.5 GT/s to prevent damage
>   PCI: rockchip-host: comment danger of 5.0 GT/s speed
>   arm64: dts: rockchip: remove dangerous max-link-speed from helios64
>   arm64: dts: rockchip: remove redundant max-link-speed from nanopi-r4s
> 
>  arch/arm64/boot/dts/rockchip/rk3399-kobol-helios64.dts |  1 -
>  arch/arm64/boot/dts/rockchip/rk3399-nanopi-r4s.dtsi    |  1 -
>  drivers/pci/controller/pcie-rockchip-host.c            |  3 +++
>  drivers/pci/controller/pcie-rockchip.c                 | 10 ++++++++--
>  4 files changed, 11 insertions(+), 4 deletions(-)