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SubjectRe: [PATCH v2 5/6] thermal/drivers/mediatek/lvts_thermal: Don't leave threshold zeroed
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On 04/05/2023 02:48, Nícolas F. R. A. Prado wrote:
> The thermal framework might leave the low threshold unset if there
> aren't any lower trip points. This leaves the register zeroed, which
> translates to a very high temperature for the low threshold. The
> interrupt for this threshold is then immediately triggered, and the
> state machine gets stuck, preventing any other temperature monitoring
> interrupts to ever trigger.
>
> (The same happens by not setting the Cold or Hot to Normal thresholds
> when using those)
>
> Set the unused threshold to a valid low value. This value was chosen so
> that for any valid golden temperature read from the efuse, when the
> value is converted to raw and back again to milliCelsius, the result
> doesn't underflow.
>
> Fixes: f5f633b18234 ("thermal/drivers/mediatek: Add the Low Voltage Thermal Sensor driver")
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
>
> ---
>
> Changes in v2:
> - Added this commit
>
> drivers/thermal/mediatek/lvts_thermal.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/thermal/mediatek/lvts_thermal.c b/drivers/thermal/mediatek/lvts_thermal.c
> index efd1e938e1c2..951a4cb75ef6 100644
> --- a/drivers/thermal/mediatek/lvts_thermal.c
> +++ b/drivers/thermal/mediatek/lvts_thermal.c
> @@ -82,6 +82,8 @@
> #define LVTS_HW_SHUTDOWN_MT8195 105000
> #define LVTS_HW_SHUTDOWN_MT8192 105000
>
> +#define LVTS_MINIUM_THRESHOLD 20000

MINIMUM

So if the thermal zone reaches 20°C, the interrupt fires, the set_trips
sets again 20°C but the interrupt won't fire until the temperature goes
above 20°C and then crosses the temperature low threshold the way down
again?

> static int golden_temp = LVTS_GOLDEN_TEMP_DEFAULT;
> static int coeff_b = LVTS_COEFF_B;
>
> @@ -309,6 +311,11 @@ static int lvts_set_trips(struct thermal_zone_device *tz, int low, int high)
> pr_debug("%s: Setting low limit temperature interrupt: %d\n",
> thermal_zone_device_type(tz), low);
> writel(raw_low, LVTS_OFFSETL(base));
> + } else {
> + pr_debug("%s: Setting low limit temperature to minimum\n",
> + thermal_zone_device_type(tz));
> + raw_low = lvts_temp_to_raw(LVTS_MINIUM_THRESHOLD);
> + writel(raw_low, LVTS_OFFSETL(base));

That's duplicate code:

u32 raw_low = lvts_temp_to_raw(low != -INT_MAX ? low :
LVTS_MINIMUM_THRESHOLD);

And then the condition in the code goes away:
if (low != -INT_MAX) {
}

> }
>
> /*

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