[PATCH v2 2/2] thermal/drivers/mediatek/lvts_thermal: Make reset optional for MT8196

[AngeloGioacchino Del Regno]

Depending on the SoC+Firmware combination, the LVTS hardware may be
may be actively used by one or even multiple concurrent MCUs!
In this case, resetting it may produce either a severe slowdown of
the entire system, or even a thermal protection AP reset, as some
MCU(s) may be reading a very high or very low temperature while the
LVTS is being reset.

On those, don't fail if no reset is found as that may be omitted on
purpose, but still check if there's one, because some board(s) may
be running on a different bootchain with reduced firmwares or using
firmwares with reduced functionality.

So, use devm_reset_control_get_optional_exclusive() instead, as the
LVTS controller always had only one reset and retrieving that by
index, specifically, always made little sense anyway.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
---
 drivers/thermal/mediatek/lvts_thermal.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/mediatek/lvts_thermal.c b/drivers/thermal/mediatek/lvts_thermal.c
index 92711896ce24..8b779fc5e970 100644
--- a/drivers/thermal/mediatek/lvts_thermal.c
+++ b/drivers/thermal/mediatek/lvts_thermal.c
@@ -1473,7 +1473,20 @@ static int lvts_probe(struct platform_device *pdev)
 	if (IS_ERR(lvts_td->base))
 		return dev_err_probe(dev, PTR_ERR(lvts_td->base), "Failed to map io resource\n");
 
-	lvts_td->reset = devm_reset_control_get_by_index(dev, 0);
+	/*
+	 * Depending on the SoC+Firmware combination, the LVTS hardware may be
+	 * may be actively used by one or even multiple concurrent MCUs!
+	 * In this case, resetting it may produce either a severe slowdown of
+	 * the entire system, or even a thermal protection AP reset, as some
+	 * MCU(s) may be reading a very high or very low temperature while the
+	 * LVTS is being reset.
+	 *
+	 * On those, don't fail if no reset is found as that may be omitted on
+	 * purpose, but still check if there's one, because some board(s) may
+	 * be running on a different bootchain with reduced firmwares or using
+	 * firmwares with reduced functionality.
+	 */
+	lvts_td->reset = devm_reset_control_get_optional_exclusive(dev, NULL);
 	if (IS_ERR(lvts_td->reset))
 		return dev_err_probe(dev, PTR_ERR(lvts_td->reset), "Failed to get reset control\n");
 
-- 
2.55.0