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

Dragan Simic
2025-11-18T08:46:28Z

Hello Geraldo,

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

On Monday, November 17, 2025 22:46 CET, Geraldo Nascimento <geraldogabriel@gmail.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@gmail.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@manjaro.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(-)