On 24-06-13, Marek Vasut wrote: > On 6/11/24 5:01 AM, Peng Fan wrote: > > [...] > > > > > > 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 > > I think the bootloader should always configure the minimal common > configuration, i.e. nominal voltage, nominal clock, so that it would achieve > maximum compatibility with any SoC in that SoC line up. > > If the user does need overdrive configuration, they should specify that in > their board DT. +1 > Keep in mind, the kernel is easy to update (including kernel DT), the > bootloader is not easy to update (esp. in field, bootloader update may > render a system unbootable if it fails). I would say, it is better to keep > the complicated things out of the bootloader if at all possible. > > > If introduce x.dtsi and x-overdrive.dtsi, how to let board choose which dtsi > > to include? > > #include "x.dtsi" > or > #include "x-overdrive.dtsi" > > But I think your question is -- how to do that at runtime ? > > U-Boot can apply DT overlays onto DT that is passed to Linux, so if the user > has board variants where they need both nonoverdrive/overdrive options, they > can apply DT overlay which enables the overdrive mode on boards which need > it. This can be done from U-Boot boot.scr or similar boot script, which can > again be easily updated, without the need to update the bootloader itself > (if something goes wrong or needs to be changed in the future). +1 for the runtime configuration via overlay as well. The overlay can be generated very easily by including the x-overdrive.dtsi into a .dtso and for those who want to run in overdrive mode always they can mae use of the x-overdrive.dtsi directly within the .dts file. Regards, Marco
