On Fri, May 9, 2014 at 4:21 PM, Vivek Gautam <gautam.vivek@xxxxxxxxxxx> wrote: > Hi Sylwester, > > > On Fri, May 9, 2014 at 3:43 PM, Sylwester Nawrocki > <s.nawrocki@xxxxxxxxxxx> wrote: >> Hi Vivek, >> >> On 08/05/14 11:03, Vivek Gautam wrote: >>>>>> diff --git a/Documentation/devicetree/bindings/phy/samsung-phy.txt b/Documentation/devicetree/bindings/phy/samsung-phy.txt >>>>>> >>> index b422e38..51efe4c 100644 >>>>>> >>> --- a/Documentation/devicetree/bindings/phy/samsung-phy.txt >>>>>> >>> +++ b/Documentation/devicetree/bindings/phy/samsung-phy.txt >>>>>> >>> @@ -114,3 +114,43 @@ Example: >>>>>> >>> compatible = "samsung,exynos-sataphy-i2c"; >>>>>> >>> reg = <0x38>; >>>>>> >>> }; >>>>>> >>> + >>>>>> >>> +Samsung Exynos5 SoC series USB DRD PHY controller >>>>>> >>> +-------------------------------------------------- >>>>>> >>> + >>>>>> >>> +Required properties: >>>>>> >>> +- compatible : Should be set to one of the following supported values: >>>>>> >>> + - "samsung,exynos5250-usbdrd-phy" - for exynos5250 SoC, >>>>>> >>> + - "samsung,exynos5420-usbdrd-phy" - for exynos5420 SoC. >>>>>> >>> +- reg : Register offset and length of USB DRD PHY register set; >>>>>> >>> +- clocks: Clock IDs array as required by the controller >>>>>> >>> +- clock-names: names of clocks correseponding to IDs in the clock property; >>>>>> >>> + Required clocks: >>>>>> >>> + - phy: main PHY clock (same as USB DRD controller i.e. DWC3 IP clock), >>>>>> >>> + used for register access. >>>>>> >>> + - ref: PHY's reference clock (usually crystal clock), used for >>>>>> >>> + PHY operations, associated by phy name. It is used to >>>>>> >>> + determine bit values for clock settings register. >>>>>> >>> + For Exynos5420 this is given as 'sclk_usbphy30' in CMU. >>>>>> >>> +- samsung,pmu-syscon: phandle for PMU system controller interface, used to >>>>>> >>> + control pmu registers for power isolation. >>>>>> >>> +- samsung,pmu-offset: phy power control register offset to pmu-system-controller >>>>>> >>> + base. >>>>> >> >>>>> >> It doesn't seem right to have register offset encoded in the device tree >>>>> >> like this. I think it'd be more appropriate to associate such an offset >>>>> >> with the compatible string's value in the driver. >>>> > >>>> > Ok, it makes more sense. >>>> > Just out of curiosity, what difference would this make ? >>> >>> Moreover, in case of Exynos5420 (and may be in future SoCs), where we >>> have 2 USB DRD PHY controllers, >>> we will need to have a way around to deal with two separate offsets in >>> the driver for one compatible string. >> >> It could be handled by creating a list of offsets per compatible string and >> then adding some way to identify the PHY device instance. So I believe that's >> not a big issue. > > True, we had tried to make use of 'aliases' for multiple controllers > on Exynos5420, > in earlier version V3 of this patch, to handle the pmu-register > offsets in _somewhat_ similar fashion. [1] > But then we had to drop that as per the suggestions in the mailing list. > >> Now you'd be encoding a list of registers offsets in the >> device tree, without encoding bit layout of each register. It's unlikely that >> each instance would have different bits layout, but describing individual >> registers in DT I thought is something that we're not supposed to do. > > Ok, so this is information to me, i was not very much aware of this. > Thanks for explaining it here. > >> >>> Getting the offsets from DT seems a cleaner way to handle this case of >>> multi controllers. >> >> I think it's easier from the driver POV, but isn't it violating the device >> tree rules ? >> Anyway. I'm just pointing this minor issue in the binding as it appears >> to me. The final word of course belongs to a DT binding maintainer. > > Thanks Sylwester, for pointing this out here. > Meantime, please let me know if the approach using aliases is one > possible solution for this or not ? I shall be sending v8 patch series for this, in order to use 'aliases' in the driver to get the distinction between pmu-offsets. So, v8 will give an alternative approach for getting pmu-offsets using macro definitions from a header file. Mark and Rob can suggest us which can be a better approach. > > > [1] [PATCH v3] phy: Add new Exynos5 USB 3.0 PHY driver > https://lkml.org/lkml/2014/1/21/46 -- Best Regards Vivek Gautam Samsung R&D Institute, Bangalore India -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
