linux-kernel - Re: [PATCH] arm64: dts: rockchip: align bindings to PCIe spec

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Message-ID: <aRglgNL5eumu4XbS@geday>
Date: Sat, 15 Nov 2025 04:02:24 -0300
From: Geraldo Nascimento <geraldogabriel@...il.com>
To: Shawn Lin <shawn.lin@...k-chips.com>
Cc: 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>,
	linux-pci <linux-pci@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	devicetree <devicetree@...r.kernel.org>,
	krzk+dt <krzk+dt@...nel.org>, conor+dt <conor+dt@...nel.org>,
	Johan Jonker <jbx6244@...il.com>,
	linux-rockchip <linux-rockchip@...ts.infradead.org>,
	Simon Glass <sjg@...omium.org>,
	Philipp Tomsich <philipp.tomsich@...ll.eu>,
	Kever Yang <kever.yang@...k-chips.com>,
	Tom Rini <trini@...sulko.com>, u-boot@...ts.denx.de,
	张烨 <ye.zhang@...k-chips.com>
Subject: Re: [PATCH] arm64: dts: rockchip: align bindings to PCIe spec

On Sat, Nov 15, 2025 at 10:21:28AM +0800, Shawn Lin wrote:
> 
> 在 2025/11/15 星期六 4:34, Geraldo Nascimento 写道:
> >> Another thing I noticed is about one commit:
> >> 114b06ee108c ("PCI: rockchip: Set Target Link Speed to 5.0 GT/s before
> >> retraining")
> >>
> >> It said: "Rockchip controllers can support up to 5.0 GT/s link speed."
> >> But we issued an errata long time ago to announced it doesn't, you could
> >> also check the PCIe part of RK3399 datasheet:
> >> https://opensource.rock-chips.com/images/d/d7/Rockchip_RK3399_Datasheet_V2.1-20200323.pdf
> > 
> > OK, I'm partly responsible for that as author of the commit in question.
> > 
> > First off let me say I do not intend to send any patches setting
> > max-link-speed to TWO for this platform.
> > 
> > I understand you issued an erratum, but are you absolutely sure about
> > that erratum? Because my testing shows otherwise:
> 
> Sure.
> 
> The reason is that Gen2 is merely functional, but this does not mean it 
> is 100% production-ready. It has some inherent issues that cannot be 
> resolved, which may lead to failures beyond imagination. Even if the 
> probability of occurrence is as low as 1 in 100,000. I cannot share 
> further details. Therefore, the official documentation should be your 
> primary reference, rather than relying solely on simple evaluations.

Hi Shawn,

indeed, the situation is not favorable and we should strive to make
amends. I'm sorry I based the commit on outdated information, I was
none the wiser.

What I propose is to add a comment to driver core saying that path
to 5.0 GT/s shouldn't be taken and users are strongly discouraged to
mess with the maximum link speed in DT.

We deal with corner case of helios64 in another patch and make sure
there are no DTs engaging 5.0 GT/s.

This should close the loop-hole.

Regards,
Geraldo Nascimento