On Tue, Dec 18, 2018 at 6:22 PM Thinh Nguyen <thinh.nguyen@xxxxxxxxxxxx> wrote: > > Hi Rob, > > On 12/18/2018 8:39 AM, Rob Herring wrote: > > On Fri, Dec 07, 2018 at 06:27:30PM -0800, Thinh Nguyen wrote: > >> This patch introduces property "snps,refclk-period-ns" to inform the > >> controller of the reference clock period. If the reference clock period > >> is different from the default Core Consultant setting, then this > >> property can be set to the reference clock period. > >> > >> This property does not control the reference clock rate. The controller > >> uses this value to perform internal timing calculations that are based > >> on the reference clock. > >> > >> Signed-off-by: Thinh Nguyen <thinhn@xxxxxxxxxxxx> > >> --- > >> Changes in v2: > >> - Split from "usb: dwc3: Add reference clock properties" > >> - Revise commit message and property description > >> > >> Documentation/devicetree/bindings/usb/dwc3.txt | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >> diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt > >> index 8e5265e9f658..b7e67edff9b2 100644 > >> --- a/Documentation/devicetree/bindings/usb/dwc3.txt > >> +++ b/Documentation/devicetree/bindings/usb/dwc3.txt > >> @@ -99,6 +99,8 @@ Optional properties: > >> this and tx-thr-num-pkt-prd to a valid, non-zero value > >> 1-16 (DWC_usb31 programming guide section 1.2.3) to > >> enable periodic ESS TX threshold. > >> + - snps,refclk-period-ns: if set, this value informs the controller of the > >> + reference clock period in nanoseconds. > > Shouldn't you be able to retrieve the refclk frequency and then > > calculate the period? > > The thing is we cannot determine the ref_clk frequency for some devices > that don't specify their clocks. So I think we should have an option to > inform the controller of the ref_clk period for those devices. Specifying the clock should be mandatory (if you want/need this feature). It just requires a fixed-clock node at a minimum. Rob
