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

[Felipe Balbi <balbi@kernel.org>]

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Hi,

Thinh Nguyen <Thinh.Nguyen@synopsys.com> writes:
> Rob Herring wrote:
>> 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.
>
> 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.

I agree. In USB land we should refer solely to the USB specification
naming schemes.

-- 
balbi

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