[PATCH v2] arm64: dts: imx8mp: Add DT nodes for the two ISPs

[Peng Fan]

> Subject: Re: [PATCH v2] arm64: dts: imx8mp: Add DT nodes for the two ISPs
> 
> On 6/11/24 3:04 AM, Peng Fan wrote:
> >> Subject: Re: [PATCH v2] arm64: dts: imx8mp: Add DT nodes for the two
> >> ISPs
> >>>>
> >>>>> Something like
> >>>>> ---8<---
> >>>>> --- a/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> >>>>> +++ b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> >>>>> @@ -1837,11 +1837,13 @@ media_blk_ctrl: blk-ctrl at 32ec0000 {
> >>>>>                                                    <&clk IMX8MP_CLK_MEDIA_APB>,
> >>>>>                                                    <&clk IMX8MP_CLK_MEDIA_DISP1_PIX>,
> >>>>>                                                    <&clk
> >>>>> IMX8MP_CLK_MEDIA_DISP2_PIX>,
> >>>>> +                                                 <&clk
> >>>>> + IMX8MP_CLK_MEDIA_ISP>,
> >>>>>                                                    <&clk IMX8MP_VIDEO_PLL1>;
> >>>>>                                  assigned-clock-parents = <&clk
> >> IMX8MP_SYS_PLL2_1000M>,
> >>>>>                                                           <&clk IMX8MP_SYS_PLL1_800M>,
> >>>>>                                                           <&clk IMX8MP_VIDEO_PLL1_OUT>,
> >>>>> -                                                        <&clk IMX8MP_VIDEO_PLL1_OUT>;
> >>>>> +                                                        <&clk IMX8MP_VIDEO_PLL1_OUT>,
> >>>>> +                                                        <&clk
> >>>>> + IMX8MP_SYS_PLL2_500M>;
> >>>>>                                  assigned-clock-rates = <500000000>, <200000000>,
> >>>>>                                                         <0>, <0>,
> >>>>> <1039500000>;
> >>>>
> >>
> >> According to the i.MX8MP Data sheet, the nominal speed for
> >> MEDIA_ISP_CLOCL_ROOT is 400MHZ with 500MHz being allowed in
> overdrive
> >> mode.
> >>
> >> I think this clock rate should drop to  the nominal value of 400MHz
> >> and those boards who support overdrive can increase it to 500MHz to
> >> avoid stiability issues and/or running out of spec.  I created an
> >> imx8mm and imx8mn- overdrive.dtsi file.  If there is interest, I can do the
> same for the 8MP as well.
> >>
> >> I haven't gone through all the clocks to determine if/what clocks are
> >> being overdriven.
> >
> > Shouldn't the bootloader take the work to runtime update the freq?
> > Why need introduce an extra overdrive.dtsi?
> 
> Shouldn't the overdrive/non-overdrive decision be done in board DT instead ?

It is bootloader configure voltage to nominal, then bootloader should use
nominal device tree or runtime update dtb.
If bootloader configure voltage to over-drive, bootloader could use
nominal or over-drive dtb

If introduce x.dtsi and x-overdrive.dtsi, how to let board choose which dtsi
to include?

Regards,
Peng.