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

Shawn Lin
2025-11-15T02:57:03Z

在 2025/11/15 星期六 4:34, Geraldo Nascimento 写道:
> On Fri, Nov 14, 2025 at 05:16:21PM +0800, Shawn Lin wrote:
>> Don't worry, it's helpful, so I think Ye could have a look.
>> May I ask if the failure only happened to one specific board?
>
> Hi Shawn,
>
> Yes, testing is restricted to my Radxa Rock Pi N10 board.
>
>>
>> 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.

>
> ---
> With max-link-speed = <2>
> pci 0000:01:00.0: 16.000 Gb/s available PCIe bandwidth, limited by 5.0 GT/s PCIe x4 link at 0000:00:00.0 (capable of 31.504 Gb/s with 8.0 GT/s PCIe x4 link)
>
> /dev/nvme0n1:
> Timing cached reads: 3002 MB in 2.00 seconds = 1502.21 MB/sec
> Timing buffered disk reads: 2044 MB in 3.00 seconds = 680.79 MB/sec
> ---
> With max-link-speed = <1>
> pci 0000:01:00.0: 8.000 Gb/s available PCIe bandwidth, limited by 2.5 GT/s PCIe x4 link at 0000:00:00.0 (capable of 31.504 Gb/s with 8.0 GT/s PCIe x4 link)
>
> /dev/nvme0n1:
> Timing cached reads: 2730 MB in 2.00 seconds = 1366.15 MB/sec
> Timing buffered disk reads: 2028 MB in 3.00 seconds = 675.71 MB/sec
> ---
>
> As you can see, not only the kernel PCI driver recognizes 5.0 GT/s PCIe
> link but there's even a marginal increase in cached reads as measured by
> hdparm, the gains are of course limited by CPU performance.
>
>> Also we set max-link-speed to ONE in rk3399-base.dtsi but seems another
>> patch slip in: 755fff528b1b ("arm64: dts: rockchip: add variables for
>> pcie completion to helios64")
>
> I can't speak for patches I haven't authored, but I believe you're
> welcome to send a correction.
>
> Thank you,
> Geraldo Nascimento
>