thermal/drivers/mediatek/lvts: Disable monitor mode during suspend

When configured in filtered mode, the LVTS thermal controller will
monitor the temperature from the sensors and trigger an interrupt once a
thermal threshold is crossed.

Currently this is true even during suspend and resume. The problem with
that is that when enabling the internal clock of the LVTS controller in
lvts_ctrl_set_enable() during resume, the temperature reading can glitch
and appear much higher than the real one, resulting in a spurious
interrupt getting generated.

Disable the temperature monitoring and give some time for the signals to
stabilize during suspend in order to prevent such spurious interrupts.

Cc: [email protected]
Reported-by: Hsin-Te Yuan <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Fixes: 8137bb9 ("thermal/drivers/mediatek/lvts_thermal: Add suspend and resume")
Reviewed-by: AngeloGioacchino Del Regno <[email protected]>
Signed-off-by: Nícolas F. R. A. Prado <[email protected]>
Link: https://lore.kernel.org/r/20250113-mt8192-lvts-filtered-suspend-fix-v2-1-07a25200c7c6@collabora.com
Signed-off-by: Daniel Lezcano <[email protected]>

Author: nfraprado

drivers/thermal/mediatek/lvts_thermal.c

@@ -860,6 +860,32 @@ static int lvts_ctrl_init(struct device *dev, struct lvts_domain *lvts_td,
 	return 0;
 }
 
+static void lvts_ctrl_monitor_enable(struct device *dev, struct lvts_ctrl *lvts_ctrl, bool enable)
+{
+	/*
+	 * Bitmaps to enable each sensor on filtered mode in the MONCTL0
+	 * register.
+	 */
+	static const u8 sensor_filt_bitmap[] = { BIT(0), BIT(1), BIT(2), BIT(3) };
+	u32 sensor_map = 0;
+	int i;
+
+	if (lvts_ctrl->mode != LVTS_MSR_FILTERED_MODE)
+		return;
+
+	if (enable) {
+		lvts_for_each_valid_sensor(i, lvts_ctrl)
+			sensor_map |= sensor_filt_bitmap[i];
+	}
+
+	/*
+	 * Bits:
+	 *      9: Single point access flow
+	 *    0-3: Enable sensing point 0-3
+	 */
+	writel(sensor_map | BIT(9), LVTS_MONCTL0(lvts_ctrl->base));
+}
+
 /*
  * At this point the configuration register is the only place in the
  * driver where we write multiple values. Per hardware constraint,
@@ -1381,8 +1407,11 @@ static int lvts_suspend(struct device *dev)
 
 	lvts_td = dev_get_drvdata(dev);
 
-	for (i = 0; i < lvts_td->num_lvts_ctrl; i++)
+	for (i = 0; i < lvts_td->num_lvts_ctrl; i++) {
+		lvts_ctrl_monitor_enable(dev, &lvts_td->lvts_ctrl[i], false);
+		usleep_range(100, 200);
 		lvts_ctrl_set_enable(&lvts_td->lvts_ctrl[i], false);
+	}
 
 	clk_disable_unprepare(lvts_td->clk);
 
@@ -1400,8 +1429,11 @@ static int lvts_resume(struct device *dev)
 	if (ret)
 		return ret;
 
-	for (i = 0; i < lvts_td->num_lvts_ctrl; i++)
+	for (i = 0; i < lvts_td->num_lvts_ctrl; i++) {
 		lvts_ctrl_set_enable(&lvts_td->lvts_ctrl[i], true);
+		usleep_range(100, 200);
+		lvts_ctrl_monitor_enable(dev, &lvts_td->lvts_ctrl[i], true);
+	}
 
 	return 0;
 }