RE: [PATCH 1/4] arm64: dts: imx8mm-venice-gw700x: override thermal cfg for industrial temp

[Jacky Bai <ping.bai@nxp.com>]

> Subject: Re: [PATCH 1/4] arm64: dts: imx8mm-venice-gw700x: override
> thermal cfg for industrial temp
> 
> On 04.06.21 17:42, Tim Harvey wrote:
> > On Wed, Jun 2, 2021 at 12:11 AM Frieder Schrempf
> > <frieder.schrempf@kontron.de> wrote:
> >>
> >> On 01.06.21 19:49, Tim Harvey wrote:
> >>> Override the default temperature alert/crit for Industrial temp
> >>> IMX8M Mini.
> >>>
> >>> Signed-off-by: Tim Harvey <tharvey@gateworks.com>
> >>> ---
> >>>  .../boot/dts/freescale/imx8mm-venice-gw700x.dtsi     | 12
> ++++++++++++
> >>>  1 file changed, 12 insertions(+)
> >>>
> >>> diff --git a/arch/arm64/boot/dts/freescale/imx8mm-venice-gw700x.dtsi
> >>> b/arch/arm64/boot/dts/freescale/imx8mm-venice-gw700x.dtsi
> >>> index c769fadbd008..512b76cd7c3b 100644
> >>> --- a/arch/arm64/boot/dts/freescale/imx8mm-venice-gw700x.dtsi
> >>> +++ b/arch/arm64/boot/dts/freescale/imx8mm-venice-gw700x.dtsi
> >>> @@ -493,3 +493,15 @@
> >>>               >;
> >>>       };
> >>>  };
> >>> +
> >>> +&cpu_alert0 {
> >>> +     temperature = <95000>;
> >>> +     hysteresis = <2000>;
> >>> +     type = "passive";
> >>> +};
> >>> +
> >>> +&cpu_crit0 {
> >>> +     temperature = <105000>;
> >>> +     hysteresis = <2000>;
> >>> +     type = "critical";
> >>> +};
> >>
> >> As this is not really board-specific, I think the proper way to handle this for
> all boards is to let the thermal driver read the temperature grading from the
> OTP fuses and set the trip-points accordingly, similar to what is done on i.MX6
> [1].
> >>
...
> >
> > Frieder,
> >
> > Yes, I thought about adding that kind of support to imx8mm_thermal.c
> > but the difference is that imx8mm has alerts defined by dt and imx6
> > does not so is it right to override dt alerts on imx8m? What if
> > someone designs a board that they specifically want a lower alert than
> > the cpu grade they are using based on something else on the board?
> >
> > My approach to this was to eventually actually adjust the imx8m dt
> > alerts in boot firmware based on some boot firmware setting or
> > specific board support and leave the kernel alone.
> 
> Allowing board-specific trip points sounds like a valid request, but I still think
> we need a way to handle the temperature grading in the driver if no
> board-specific trip-points are given.
> 
> What if we just set the temperature property in the trip nodes in imx8mm.dtsi
> to zero? The thermal driver would detect this and setup the correct values
> according to the grading. If the dt already provides non-zero temperature
> values (through the board dts) the driver will just leave the values and
> disregard the grading.
> 
> I think this solution would be covering all needs.

I thought to add the grading check in the imx8mm_thermal.c to dynamically set the trip points
temp, but it seems hard to do it due to the fact of_thermal is used, as no helper API is exported by
of_thermal, no better way to override the trip point temp.

glad to see any good suggestions.

BR
Jacky Bai 

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