Hi,

Thinh Nguyen [off-list ref] writes:

Rob Herring wrote:

quoted

On Mon, Jul 20, 2020 at 11:01 PM Thinh Nguyen [off-list ref] wrote:

quoted

Rob Herring wrote:

quoted

On Thu, Jul 16, 2020 at 02:59:08PM -0700, Thinh Nguyen wrote:

quoted

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 <redacted>
---
   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