Re: [PATCH 0/6] arm64: dts: freescale: imx8mp-skov: switch to nominal drive mode

[Peng Fan <peng.fan@oss.nxp.com>]

On Thu, Dec 19, 2024 at 08:27:31AM +0100, Ahmad Fatoum wrote:
>Unlike the i.MX8MM and i.MX8MN SoCs added earlier, the imx8mp.dtsi
>configures some clocks at frequencies that are only validated for
>overdrive mode, i.e., when VDD_SOC is 950 mV.
>
>For the Skov i.MX8MP board, we want to run the SoC at the lower voltage of
>850 mV though to reduce heat generation and power usage. For this to work,
>clock rates need to adhere to the limits of the nominal drive mode.
>
>This is done by this series: A new imx8mp-nominal.dtsi reconfigures
>the imx8mp.dtsi clock tree to be compatible with nominal mode, an adaptation
>to the Linux clock driver makes it sanity check the actual clock rates against
>the SoC operating mode's constraints and finally the Skov DT makes use
>of it.
>
>Actual configuration of the VDD_SOC rail continues to happen prior to Linux
>as well as PLL configuration that needs to happen earlier than the kernel
>running. See the corresponding barebox patch series[1] for details.
>Note that the barebox series didn't yet include VDD_SOC reconfiguration
>to 850mV, that would follow once the kernel changes have been merged.

Good to see this. I had same plan to support i.MX9.

I see you introduce a new property, how about using a boot pararmeter,
saying "mode=nominal" or "mode=overdrive". Then drivers could
act accordingly.

Regards,
Peng

>
>[1]: https://lore.kernel.org/barebox/20240503103717.1370636-1-a.fatoum@pengutronix.de/
>
>---
>Ahmad Fatoum (6):
>      dt-bindings: clock: imx8m: document nominal/overdrive properties
>      arm64: dts: imx8mp: Add optional nominal drive mode DTSI
>      arm64: dts: imx8mp: add fsl,nominal-mode property into nominal.dtsi
>      arm64: dts: freescale: imx8mp-skov: fix LDB clock rate configuration
>      arm64: dts: freescale: imx8mp-skov: operate SoC in nominal mode
>      clk: imx8mp: inform CCF of maximum frequency of clocks
>
> .../devicetree/bindings/clock/imx8m-clock.yaml     |  14 ++
> arch/arm64/boot/dts/freescale/imx8mp-nominal.dtsi  |  64 +++++++++
> .../arm64/boot/dts/freescale/imx8mp-skov-reva.dtsi |   5 +-
> .../freescale/imx8mp-skov-revb-mi1010ait-1cp1.dts  |  19 +--
> drivers/clk/imx/clk-imx8mp.c                       | 147 +++++++++++++++++++++
> 5 files changed, 233 insertions(+), 16 deletions(-)
>---
>base-commit: 78d4f34e2115b517bcbfe7ec0d018bbbb6f9b0b8
>change-id: 20241217-imx8m-clk-9467763dfcd8
>
>Best regards,
>-- 
>Ahmad Fatoum <a.fatoum@pengutronix.de>
>