RE: [PATCH v4 1/2] dt-bindings: pci: Retrain Link to work around Gen2 training defect.

[Athani Nadeem Ladkhan <nadeem@cadence.com>]

Hi Rob / Kishon,

> -----Original Message-----
> From: Rob Herring <robh@kernel.org>
> Sent: Friday, December 11, 2020 10:32 PM
> To: Athani Nadeem Ladkhan <nadeem@cadence.com>
> Cc: Tom Joseph <tjoseph@cadence.com>; Lorenzo Pieralisi
> <lorenzo.pieralisi@arm.com>; Bjorn Helgaas <bhelgaas@google.com>; PCI
> <linux-pci@vger.kernel.org>; linux-kernel@vger.kernel.org; Kishon Vijay
> Abraham I <kishon@ti.com>; devicetree@vger.kernel.org; Milind Parab
> <mparab@cadence.com>; Swapnil Kashinath Jakhade
> <sjakhade@cadence.com>; Parshuram Raju Thombare
> <pthombar@cadence.com>
> Subject: Re: [PATCH v4 1/2] dt-bindings: pci: Retrain Link to work around
> Gen2 training defect.
> 
> EXTERNAL MAIL
> 
> 
> On Fri, Dec 11, 2020 at 9:03 AM Nadeem Athani <nadeem@cadence.com>
> wrote:
> >
> > Cadence controller will not initiate autonomous speed change if
> > strapped as Gen2. The Retrain Link bit is set as quirk to enable this speed
> change.
> > Adding a quirk flag based on a new compatible string.
> >
> > Signed-off-by: Nadeem Athani <nadeem@cadence.com>
> > ---
> >  Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml | 4
> > +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git
> > a/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml
> > b/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml
> > index 293b8ec318bc..204d78f9efe3 100644
> > --- a/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml
> > +++ b/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml
> > @@ -15,7 +15,9 @@ allOf:
> >
> >  properties:
> >    compatible:
> > -    const: cdns,cdns-pcie-host
> > +    enum:
> > +        - cdns,cdns-pcie-host
> > +        - cdns,cdns-pcie-host-quirk-retrain
> 
> So, we'll just keep adding quirk strings on to the compatible? I don't think so.
> Compatible strings should map to a specific implementation/platform and
> quirks can then be implied from them. This is the only way we can implement
> quirks in the OS without firmware
> (DT) changes.
Ok, I will change the compatible string to " ti,j721e-pcie-host" in place of  " cdns,cdns-pcie-host-quirk-retrain" .
@Kishon Vijay Abraham I: Is this fine? Or will you suggest an appropriate name?

Nadeem
> 
> Rob