[RFC PATCH 07/11] arm64: dts: imx8mp: fix VPU_BUS clock setting

[Adam Ford]

On Fri, May 2, 2025 at 11:55 AM Marco Felsch <m.felsch at pengutronix.de> wrote:
>
> On 25-05-02, Adam Ford wrote:
> > On Fri, May 2, 2025 at 10:10 AM Marco Felsch <m.felsch at pengutronix.de> wrote:
> > >
> > > The VPU_PLL clock must be set before the VPU_BUS clock which is derived
> > > from the VPU_PLL clock else the VPU_BUS clock is 300MHz and not 600MHz.

I did verify the current clock rate ends up at 300MHz instead of the
desired 600 or 800MHz, so we should do something.

> > >
> > > Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
> > > ---
> > >  arch/arm64/boot/dts/freescale/imx8mp.dtsi | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/arm64/boot/dts/freescale/imx8mp.dtsi b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> > > index 97b09b647ec7..7f4bdefb3480 100644
> > > --- a/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> > > +++ b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> > > @@ -2289,8 +2289,8 @@ vpumix_blk_ctrl: blk-ctrl at 38330000 {
> > >                                  <&clk IMX8MP_CLK_VPU_G2_ROOT>,
> > >                                  <&clk IMX8MP_CLK_VPU_VC8KE_ROOT>;
> > >                         clock-names = "g1", "g2", "vc8000e";
> > > -                       assigned-clocks = <&clk IMX8MP_CLK_VPU_BUS>, <&clk IMX8MP_VPU_PLL>;
> > > -                       assigned-clock-parents = <&clk IMX8MP_VPU_PLL_OUT>;
> > > +                       assigned-clocks = <&clk IMX8MP_VPU_PLL>, <&clk IMX8MP_CLK_VPU_BUS>;
> > > +                       assigned-clock-parents = <0>, <&clk IMX8MP_VPU_PLL_OUT>;
> > >                         assigned-clock-rates = <600000000>, <600000000>;
> >
> > I think there was a move to make the default be overdrive [1]  and [2]
> > and use a 'nominal' device tree for those who are not in overdrive
> > mode.  According to the TRM, the VPU_BUS_CLK_ROOT, the nominal is
> > 600MHz and the overdrive is 800MHz.  Based on that, I wonder if the
> > values here should be 800MHz and if we should add the nominal values
> > of 600MHz to the imx8m-nominal.dtsi file.
>
> You're right, Ahamd and Lucas did change this. I will adapt it later on.

I updated my device tree to run in overdrive mode and ran fluster at
the higher rates:
VPU_G1 - 800MHz,
VPU-G2 - 700MHz
VPU-Bus - 800MHz

./fluster.py run -d GStreamer-VP8-V4L2SL-Gst1.0
Ran 57/61 tests successfully               in 5.922 secs
(vs 7.059 secs at nominal speed)

./fluster.py run -dGStreamer-H.264-V4L2SL-Gst1.0
Ran 129/135 tests successfully               in 40.107 secs
(vs 45.741 secs at nominal speed)

If you want, I can submit the clock updates I have for overdrive or
send them to you to save you some time.

adam

>
> Regards,
>   Marco