linux-kernel - Re: [PATCH v2 1/1] PCI: imx6: Add pcie compliance test option

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Date:   Mon, 19 Jun 2017 06:43:58 +0000
From:   Schöfegger Stefan 
        <Stefan.Schoefegger@...zinger.com>
To:     Fabio Estevam <festevam@...il.com>
CC:     Bjorn Helgaas <helgaas@...nel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Richard Zhu <hongxing.zhu@....com>,
        "Arnd Bergmann" <arnd@...db.de>,
        open list <linux-kernel@...r.kernel.org>,
        "Kishon Vijay Abraham I" <kishon@...com>,
        Jingoo Han <jingoohan1@...il.com>,
        "Bjorn Helgaas" <bhelgaas@...gle.com>,
        "moderated list:PCI DRIVER FOR IMX6" 
        <linux-arm-kernel@...ts.infradead.org>,
        Lucas Stach <l.stach@...gutronix.de>
Subject: Re: [PATCH v2 1/1] PCI: imx6: Add pcie compliance test option

On Wednesday, June 14, 2017 4:11:29 PM CEST Fabio Estevam wrote:
> On Wed, Jun 14, 2017 at 2:52 AM, Schöfegger Stefan
> 
> <Stefan.Schoefegger@...zinger.com> wrote:
> > device). The bitrate and de-emphasis must be switched. The driver (without
> > this patches) does not allow to switch to gen2 because it falls back to
> > gen1. It is impossible to generate the gen2 test pattern.
> 
> If you pass 'fsl,max-link-speed = <2>;' in your device tree, then it
> will allow gen2.
> 
> From Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt:
> 
> "- fsl,max-link-speed: Specify PCI gen for link capability. Must be '2' for
>   gen2, otherwise will default to gen1. Note that the IMX6 LVDS clock
> outputs do not meet gen2 jitter requirements and thus for gen2 capability a
> gen2 compliant clock generator should be used and configured."
> 
> Wouldn't this solve the problem?

No, it only sets the maximum allowed link speed but it is forced to gen1 
before.

During compliance test there is no real link established and there is no link 
speed negotiation, the phy is in a special compliance test state.

Stefan