Rob Herring wrote: > On Tue, Jul 21, 2020 at 10:42 AM Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx> wrote: >> Rob Herring wrote: >>> On Mon, Jul 20, 2020 at 11:01 PM Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx> 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@xxxxxxxxxxxx> >>>>>> --- >>>>>> 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. >> That may confuse the user because now we'd use 'super-speed-plus' to >> define the speed of the lane rather than the device itself. >> >> According to the USB 3.2 spec, super-speed-plus can mean gen2x1, gen1x2, >> or gen2x2. > Then add new strings as needed to make it clear: super-speed-plus-gen1x2 > > It's obvious that what 'super-speed-plus' means is not clear since > USB-IF extended its meaning. > > Rob If we introduce a new enum for gen1x2, now we'd have to go back and inspect all the checks for all the drivers where for example speed == USB_SPEED_SUPER_PLUS. It seems to be more clunky and may introduce more bugs. BR, Thinh
