There are three thermal stages defined in the PMIC:

stage 1: warning
stage 2: system should shut down
stage 3: emergency shut down

By default the PMIC assumes that the OS isn't doing anything and thus
at stage 2 it does a partial PMIC shutdown and at stage 3 it kills
all power. When switching between thermal stages the PMIC generates an
interrupt which is handled by the driver. The partial PMIC shutdown at
stage 2 can be disabled by software, which allows the OS to initiate a
shutdown at stage 2 with a thermal zone configured accordingly.

If a critical trip point is configured in the thermal zone the driver
adjusts the stage 1-3 temperature thresholds to (closely) match the
critical temperature with a stage 2 threshold (125/130/135/140 ?C).
If a suitable match is found the partial shutdown at stage 2 is
disabled. If for some reason the system doesn't shutdown at stage 2
the emergency shutdown at stage 3 kicks in.

The partial shutdown at stage 2 remains enabled in these cases:
- no critical trip point defined
- the temperature of the critical trip point is < 125?C
- the temperature of the critical trip point is > 140?C and no
  ADC channel is configured (thus the OS is not notified when the critical
  temperature is reached)

Suggested-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---
Changes in v5:
- patch added to the series
---
 drivers/thermal/qcom-spmi-temp-alarm.c | 161 ++++++++++++++++++++++---
 1 file changed, 142 insertions(+), 19 deletions(-)

diff --git a/drivers/thermal/qcom-spmi-temp-alarm.c b/drivers/thermal/qcom-spmi-temp-alarm.c
index ad4f3a8d6560..936e4dde4298 100644
--- a/drivers/thermal/qcom-spmi-temp-alarm.c
+++ b/drivers/thermal/qcom-spmi-temp-alarm.c

...

+static int qpnp_tm_update_critical_trip_temp(struct qpnp_tm_chip *chip,
+					     int temp)
+{
+	u8 reg;
+	bool disable_s2_shutdown = false;
+	int ret;
+
+	WARN_ON(!mutex_is_locked(&chip->lock));
+
+	/*
+	 * Default: S2 and S3 shutdown enabled, thresholds at
+	 * 105C/125C/145C, monitoring at 25Hz
+	 */
+	reg = SHUTDOWN_CTRL1_RATE_25HZ;
+
+	if ((temp == THERMAL_TEMP_INVALID) ||
+	    (temp < STAGE2_THRESHOLD_MIN)) {
+		chip->thresh = THRESH_MIN;
+		goto skip;
+	}
+
+	if (temp <= STAGE2_THRESHOLD_MAX) {
+		chip->thresh = THRESH_MAX -
+			((STAGE2_THRESHOLD_MAX - temp) /
+			 TEMP_THRESH_STEP);
+		disable_s2_shutdown = true;
+	} else {
+		chip->thresh = THRESH_MAX;
+
+		if (!IS_ERR(chip->adc))