[PATCH] bsps/stm32h7: Allow use of max temp range

[Cedric Berger]

Hello,

On 26.07.23 22:48, Kinsey Moore wrote:
> This adds an option to allow operation of the CPU at its maximum
> temperature range of 125F by reducing the CPU clock to 400MHz instead of
> the 105F limit imposed by the default 480MHz CPU clock. This tradeoff is
> detailed in table 122 in section 7.3.1 of the STM32H743VI datasheet. The
> default remains at 480MHz/105F.

I think it is very good to reduce the CPU clock this way. Does your 
patch also results in a decrease of operating voltage from VOS0 to VOS1?

In my opinion, the default "480MHz/105F" is not very serious: at that 
frequency + temperature, the chip has an expected lifetime of < 2 years.

See: 
https://www.st.com/resource/en/application_note/an5337-stm32h7-series-lifetime-estimates-stmicroelectronics.pdf

For our product, we might even reduce the clock further to 300MHZ to be 
able to use VOS2 voltage.

All that to say that imho, 1) the default should be 400MHz, and 2) if 
there is some configuration variable, maybe it should be based on the 
voltage, like "STM23H7_VCORE", with the following values:

- "VOS0": Freq = 480 MHz (the actual default)
- "VOS1": Freq = 400 MHz (your new proposed value)
- "VOS2": Freq = 300 MHz (a very conservative setting)
- "VOS3": Freq = 200 MHz (for very low power usage)

Cedric

> ---
>   .../stm/stm32h743i-eval/stm32h7-config-osc.c   |  8 ++++++++
>   spec/build/bsps/arm/stm32h7/bspstm32h7.yml     |  2 ++
>   spec/build/bsps/arm/stm32h7/optenthermal.yml   | 18 ++++++++++++++++++
>   3 files changed, 28 insertions(+)
>   create mode 100644 spec/build/bsps/arm/stm32h7/optenthermal.yml
>
> diff --git a/bsps/arm/stm32h7/boards/stm/stm32h743i-eval/stm32h7-config-osc.c b/bsps/arm/stm32h7/boards/stm/stm32h743i-eval/stm32h7-config-osc.c
> index df55a49b3c..016f772309 100644
> --- a/bsps/arm/stm32h7/boards/stm/stm32h743i-eval/stm32h7-config-osc.c
> +++ b/bsps/arm/stm32h7/boards/stm/stm32h743i-eval/stm32h7-config-osc.c
> @@ -42,9 +42,17 @@ const RCC_OscInitTypeDef stm32h7_config_oscillator = {
>     .PLL.PLLState = RCC_PLL_ON,
>     .PLL.PLLSource = RCC_PLLSOURCE_HSE,
>     .PLL.PLLM = 5,
> +#ifdef STM32H7_OSC_ENABLE_MAX_THERMAL_RANGE
> +  .PLL.PLLN = 160,
> +#else
>     .PLL.PLLN = 192,
> +#endif
>     .PLL.PLLP = 2,
> +#ifdef STM32H7_OSC_ENABLE_MAX_THERMAL_RANGE
> +  .PLL.PLLQ = 2,
> +#else
>     .PLL.PLLQ = 12,
> +#endif
>     .PLL.PLLR = 2,
>     .PLL.PLLRGE = RCC_PLL1VCIRANGE_2,
>     .PLL.PLLVCOSEL = RCC_PLL1VCOWIDE,
> diff --git a/spec/build/bsps/arm/stm32h7/bspstm32h7.yml b/spec/build/bsps/arm/stm32h7/bspstm32h7.yml
> index 0aaf1f0cc6..2614457bcc 100644
> --- a/spec/build/bsps/arm/stm32h7/bspstm32h7.yml
> +++ b/spec/build/bsps/arm/stm32h7/bspstm32h7.yml
> @@ -13,6 +13,8 @@ install: []
>   links:
>   - role: build-dependency
>     uid: grp
> +- role: build-dependency
> +  uid: optenthermal
>   source:
>   - bsps/arm/stm32h7/boards/stm/stm32h743i-eval/stm32h7-bspstarthooks.c
>   - bsps/arm/stm32h7/boards/stm/stm32h743i-eval/stm32h7-config-clk.c
> diff --git a/spec/build/bsps/arm/stm32h7/optenthermal.yml b/spec/build/bsps/arm/stm32h7/optenthermal.yml
> new file mode 100644
> index 0000000000..ff79db213d
> --- /dev/null
> +++ b/spec/build/bsps/arm/stm32h7/optenthermal.yml
> @@ -0,0 +1,18 @@
> +SPDX-License-Identifier: CC-BY-SA-4.0 OR BSD-2-Clause
> +actions:
> +- get-boolean: null
> +- define-condition: null
> +build-type: option
> +copyrights:
> +- Copyright (C) 2023 On-Line Applications Research (OAR)
> +default:
> +- enabled-by: true
> +  value: false
> +description: |
> +  Allow use of the maximum thermal range the CPU is capable of by reducing the
> +  CPU clock to 400MHz
> +enabled-by: true
> +format: '{}'
> +links: []
> +name: STM32H7_OSC_ENABLE_MAX_THERMAL_RANGE
> +type: build