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

[Adam Ford]

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.
>
> 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.

adam

>                         interconnects = <&noc IMX8MP_ICM_VPU_G1 &noc IMX8MP_ICN_VIDEO>,
>                                         <&noc IMX8MP_ICM_VPU_G2 &noc IMX8MP_ICN_VIDEO>,


[1] - https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/arch/arm64/boot/dts/freescale/imx8mp.dtsi?h=next-20250502&id=9f7595b3e5ae0ead20a74a5f2a8f0434b3254ac5

[2] - https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/arch/arm64/boot/dts/freescale/imx8mp-nominal.dtsi?h=next-20250502&id=4b98bf3bff7353d94824c4d874ff2d7f38acc49a

> --
> 2.39.5
>
>