thermal/drivers/mediatek/lvts_thermal: Fix wrong lvts_ctrl index

In 'lvts_should_update_thresh()' and 'lvts_ctrl_start()' functions,
the parameter passed to 'lvts_for_each_valid_sensor()' macro is always
'lvts_ctrl->lvts_data->lvts_ctrl'. In other words, the array index 0
is systematically passed as 'struct lvts_ctrl_data' type item, even
when another item should be consumed instead.

Hence, the 'valid_sensor_mask' value which is selected can be wrong
because unrelated to the 'struct lvts_ctrl_data' type item that should
be used. Hence, some thermal zone can be registered for a sensor 'i'
that does not actually exist. Because of the invalid address used
as 'lvts_sensor[i].msr', this situation ends up with a crash in
'lvts_get_temp()' function, where this 'msr' pointer is passed to
'readl_poll_timeout()' function. The following message is output:
"Unable to handle kernel NULL pointer dereference at virtual
address <msr>", with <msr> = 0.

This patch fixes the issue.

Fixes: 11e6f4c3 ("thermal/drivers/mediatek/lvts_thermal: Allow early empty sensor slots")
Signed-off-by: Julien Panis <jpanis@baylibre.com>
Reviewed-by: Nicolas Pitre <npitre@baylibre.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20240503-mtk-thermal-lvts-ctrl-idx-fix-v1-2-f605c50ca117@baylibre.com

drivers/thermal/mediatek/lvts_thermal.c

@@ -116,9 +116,9 @@ struct lvts_ctrl_data {
 			      ((s2) ? BIT(2) : 0) | \
 			      ((s3) ? BIT(3) : 0))
 
-#define lvts_for_each_valid_sensor(i, lvts_ctrl_data) \
+#define lvts_for_each_valid_sensor(i, lvts_ctrl) \
 	for ((i) = 0; (i) < LVTS_SENSOR_MAX; (i)++) \
-		if (!((lvts_ctrl_data)->valid_sensor_mask & BIT(i))) \
+		if (!((lvts_ctrl)->valid_sensor_mask & BIT(i))) \
 			continue; \
 		else
 
@@ -145,6 +145,7 @@ struct lvts_ctrl {
 	const struct lvts_data *lvts_data;
 	u32 calibration[LVTS_SENSOR_MAX];
 	u32 hw_tshut_raw_temp;
+	u8 valid_sensor_mask;
 	int mode;
 	void __iomem *base;
 	int low_thresh;
@@ -356,7 +357,7 @@ static bool lvts_should_update_thresh(struct lvts_ctrl *lvts_ctrl, int high)
 	if (high > lvts_ctrl->high_thresh)
 		return true;
 
-	lvts_for_each_valid_sensor(i, lvts_ctrl->lvts_data->lvts_ctrl)
+	lvts_for_each_valid_sensor(i, lvts_ctrl)
 		if (lvts_ctrl->sensors[i].high_thresh == lvts_ctrl->high_thresh
 		    && lvts_ctrl->sensors[i].low_thresh == lvts_ctrl->low_thresh)
 			return false;
@@ -617,6 +618,8 @@ static int lvts_sensor_init(struct device *dev, struct lvts_ctrl *lvts_ctrl,
 		lvts_sensor[i].high_thresh = INT_MIN;
 	};
 
+	lvts_ctrl->valid_sensor_mask = lvts_ctrl_data->valid_sensor_mask;
+
 	return 0;
 }
 
@@ -1112,7 +1115,7 @@ static int lvts_ctrl_start(struct device *dev, struct lvts_ctrl *lvts_ctrl)
 	u32 *sensor_bitmap = lvts_ctrl->mode == LVTS_MSR_IMMEDIATE_MODE ?
 			     sensor_imm_bitmap : sensor_filt_bitmap;
 
-	lvts_for_each_valid_sensor(i, lvts_ctrl->lvts_data->lvts_ctrl) {
+	lvts_for_each_valid_sensor(i, lvts_ctrl) {
 
 		int dt_id = lvts_sensors[i].dt_id;