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Sun, 16 Nov 2025 23:02:40 -0800 (PST) Date: Mon, 17 Nov 2025 04:02:28 -0300 From: Geraldo Nascimento To: Dragan Simic Cc: Shawn Lin , Lorenzo Pieralisi , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Manivannan Sadhasivam , Rob Herring , Bjorn Helgaas , Heiko Stuebner , linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, Krzysztof Kozlowski , Conor Dooley , Johan Jonker , linux-rockchip@lists.infradead.org Subject: Re: [PATCH 0/3] PCI: rockchip: 5.0 GT/s speed may be dangerous Message-ID: References: <8f3cc1c1-7bf7-4610-b7ce-79ebd6f05a6e@rock-chips.com> <257951b7-c22e-9707-6aba-3dc5794306bb@manjaro.org> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <257951b7-c22e-9707-6aba-3dc5794306bb@manjaro.org> On Mon, Nov 17, 2025 at 04:57:11AM +0100, Dragan Simic wrote: > Hello Shawn and Geraldo, > > On Monday, November 17, 2025 04:42 CET, Shawn Lin wrote: > > 在 2025/11/15 星期六 17:10, Geraldo Nascimento 写道: > > > In recent interactions with Shawn Lin from Rockchip it came to my > > > attention there's an unknown errata regarding 5.0 GT/s operational > > > speed of their PCIe core. According to Shawn there's grave danger > > > 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. > > > > I'm not sure just adding a warn would be a good choice. Could we totally > > force to use gen1 and add a warn if trying to use Gen2. > > I think that forcing 2.5 GT/s with an appropriate warning message > is a good idea. That would be like some quirk that gets applied > automatically, to prevent data corruption, while warning people > who attempt to "overclock" the PCIe interface. Hi Shawn and Dragan, Alright, I'll send v2 with this suggestion in mind. So that driving the core at 5.0 GT/s will require patching and compiling own kernel. > > > Meanwhile amend the commit message to add a reference > > of RK3399 official datesheet[1] which says PCIe on RK3399 should only > > support 2.5GT/s? > > > > [1]https://opensource.rock-chips.com/images/d/d7/Rockchip_RK3399_Datasheet_V2.1-20200323.pdf > Shawn, URLs have the bad habit of changing or simply disappearing, so I don't think it's a good idea to put URL in the commit message. Also, the datasheet just mentions that RK3399 supports only 2.5 GT/s, it does not mention possible damage from driving the core at 5.0 GT/s. > Also, rewording the patch summary as follows below may be good, > because that would provide more details: > > PCI: rockchip: Warn about Gen2 5.0 GT/s on RK3399 being unsafe > > Or, if we'll go with the automatic downgrading, like this: > > PCI: rockchip: Limit RK3399 to Gen1 2.5 GT/s to prevent breakage > Dragan, these are good ones, thanks. Though I think I'll omit Gen1/Gen2 wording since I know how much Bjorn dislikes those terms. Thanks, Geraldo Nascimento