Re: [PATCH 06/11] usb: devicetree: dwc3: Introduce num-lanes and lsm

[Rob Herring <robh@kernel.org>]

On Mon, Jul 20, 2020 at 11:01 PM Thinh Nguyen <Thinh.Nguyen@synopsys.com> wrote:
>
> Rob Herring wrote:
> > On Thu, Jul 16, 2020 at 02:59:08PM -0700, Thinh Nguyen wrote:
> >> Introduce num-lanes and lane-speed-mantissa-gbps for devices operating
> >> in super-speed-plus. DWC_usb32 IP supports multiple lanes and can
> >> operate in different sublink speeds. Currently the device controller
> >> does not have the information of the phy's number of lanes supported. As
> >> a result, the user can specify them through these properties if they are
> >> different than the default setting.
> >>
> >> Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
> >> ---
> >>   Documentation/devicetree/bindings/usb/dwc3.txt | 9 +++++++++
> >>   1 file changed, 9 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt
> >> index d03edf9d3935..4eba0615562f 100644
> >> --- a/Documentation/devicetree/bindings/usb/dwc3.txt
> >> +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
> >> @@ -86,6 +86,15 @@ Optional properties:
> >>    - snps,quirk-frame-length-adjustment: Value for GFLADJ_30MHZ field of GFLADJ
> >>      register for post-silicon frame length adjustment when the
> >>      fladj_30mhz_sdbnd signal is invalid or incorrect.
> >> + - snps,num-lanes: set to specify the number of lanes to use. Valid inputs are
> >> +                    1 or 2. Apply if the maximum-speed is super-speed-plus
> >> +                    only. Default value is 2 for DWC_usb32. For DWC_usb31,
> >> +                    it is always 1 at super-speed-plus.
> >> + - snps,lane-speed-mantissa-gbps: set to specify the symmetric lane speed
> >> +                    mantissa in Gbps. Valid inputs are 5 or 10. Apply if
> >> +                    the maximum-speed is super-speed-plus only. Default
> >> +                    value is 10. For DWC_usb31, it's always 10 at
> >> +                    super-speed-plus.
> > This is all common USB things and should be common properties (which we
> > may already have).
>
> Sure. For "num-lanes" is simple, any objection if we use
> "lane-speed-mantissa-gbps"? Or should we add "lane-speed-exponent"?

'num-lanes' is good as that's what PCIe uses. Document that with
'maximum-speed'.

I think 'super-speed-plus' should mean gen 2 10G per lane. Then
between num-lanes and maximum-speed you can define all 4 possible
rates.

Rob