drm/nouveau/therm: force a minimum hysteresis on temperature alarm thresholds

This should avoid the situation where a user gets its kernel logs flooded when
temperature oscillates around a threshold with 0°C hysteresis.

This patch is just meant to fix broken vbios (as reported on a nv4e on
sysfs hwmon interface.

Signed-off-by: Martin Peres <martin.peres@labri.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/core/subdev/therm/temp.c

@@ -58,11 +58,18 @@ static void
 nouveau_therm_temp_safety_checks(struct nouveau_therm *therm)
 {
 	struct nouveau_therm_priv *priv = (void *)therm;
+	struct nvbios_therm_sensor *s = &priv->bios_sensor;
 
 	if (!priv->bios_sensor.slope_div)
 		priv->bios_sensor.slope_div = 1;
 	if (!priv->bios_sensor.offset_den)
 		priv->bios_sensor.offset_den = 1;
+
+	/* enforce a minimum hysteresis on thresholds */
+	s->thrs_fan_boost.hysteresis = max_t(u8, s->thrs_fan_boost.hysteresis, 2);
+	s->thrs_down_clock.hysteresis = max_t(u8, s->thrs_down_clock.hysteresis, 2);
+	s->thrs_critical.hysteresis = max_t(u8, s->thrs_critical.hysteresis, 2);
+	s->thrs_shutdown.hysteresis = max_t(u8, s->thrs_shutdown.hysteresis, 2);
 }
 
 /* must be called with alarm_program_lock taken ! */