Messages in this thread | | | From | Frank Li <> | Subject | RE: [EXT] Re: [PATCH v2 1/3] dt-bindings: usb: cdns-imx8qm: add imx8qm cdns3 glue bindings | Date | Mon, 20 Mar 2023 16:22:47 +0000 |
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> >>>>> + assigned-clocks: > >>>>> + items: > >>>>> + - description: Phandle and clock specifier of > IMX_SC_PM_CLK_PER. > >>>>> + - description: Phandle and clock specifoer of > >> IMX_SC_PM_CLK_MISC. > >>>>> + - description: Phandle and clock specifoer of > >>>> IMX_SC_PM_CLK_MST_BUS. > >>>>> + > >>>>> + assigned-clock-rates: > >>>>> + items: > >>>>> + - description: Must be 125 Mhz. > >>>>> + - description: Must be 12 Mhz. > >>>>> + - description: Must be 250 Mhz. > >>>> > >>>> I would argue that both properties above are not needed. If your > >>>> hardware requires fixed frequencies, clock provider can fix them, can't > it? > >>> > >>> Clock provider don't know fixed value and turn on only used by client. > >> > >> So maybe fix the clock provider? Or this device driver? Requiring by > >> binding specific frequencies for every board is a bit redundant. > > > > It is not for every boards, it is common for a chip family. Only a place to set > for > > QM and QXP. > > > > The similar case is network driver, which require a specific frequency at > clock assign. > > Generally frequency is fixed, clock source name may change at difference > chips. > > If frequency is always fixed, I don't understand why this is in DT > bindings. I would even say it should not be in DTS. We don't put into > DTS properties which are always the same, because otherwise they would > grow crazy big.
Although frequency is fixed, clock name may change for difference platform.
assigned-clocks = <&clk IMX_SC_R_USB_2 IMX_SC_PM_CLK_PER>, <&clk IMX_SC_R_USB_2 IMX_SC_PM_CLK_MISC>, <&clk IMX_SC_R_USB_2 IMX_SC_PM_CLK_MST_BUS>; assigned-clock-rates = <125000000>, <12000000>, <250000000>; some platform use IMX_SC_R_USB_2, other platform may use IMX_SC_R_USB_3.
> > Best regards, > Krzysztof
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