On 07.06.21 09:30, Jacky Bai wrote:

quoted

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:

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On Wed, Jun 2, 2021 at 12:11 AM Frieder Schrempf
[off-list ref] wrote:

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On 01.06.21 19:49, Tim Harvey wrote:

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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

++++++++++++

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 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].

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...

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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.

Right, the driver doesn't handle the trip-points directly. This is all hidden in the framework. So this might not be so easy to implement.

What about this other approach: Adding all the possible trip-points for the different gradings to the SoC-devicetree and then let the thermal driver remove the trip nodes from the dt that are not valid for the detected grading, just before the driver registers the sensor/zone.

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