linux-kernel - [PATCH v2] thermal/drivers/mediatek/lvts_thermal: Return error in case of invalid efuse data

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Date: Tue, 04 Jun 2024 18:46:58 +0200
From: Julien Panis <jpanis@...libre.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>, 
 Daniel Lezcano <daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>, 
 Lukasz Luba <lukasz.luba@....com>, 
 Matthias Brugger <matthias.bgg@...il.com>, 
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
 Nicolas Pitre <npitre@...libre.com>
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, 
 Julien Panis <jpanis@...libre.com>
Subject: [PATCH v2] thermal/drivers/mediatek/lvts_thermal: Return error in
 case of invalid efuse data

This patch prevents from registering thermal entries and letting the
driver misbehave if efuse data is invalid. A device is not properly
calibrated if the golden temperature is zero.

Fixes: f5f633b18234 ("thermal/drivers/mediatek: Add the Low Voltage Thermal Sensor driver")
Signed-off-by: Julien Panis <jpanis@...libre.com>
---
Guard against invalid calibration data, following this discussion:
https://lore.kernel.org/all/ad047631-16b8-42ce-8a8d-1429e6af4517@collabora.com/
---
Changes in v2:
- Add Fixes tag.
- Link to v1: https://lore.kernel.org/r/20240603-mtk-thermal-calib-check-v1-1-5d6bf040414c@baylibre.com
---
 drivers/thermal/mediatek/lvts_thermal.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/mediatek/lvts_thermal.c b/drivers/thermal/mediatek/lvts_thermal.c
index 0bb3a495b56e..185d5a32711f 100644
--- a/drivers/thermal/mediatek/lvts_thermal.c
+++ b/drivers/thermal/mediatek/lvts_thermal.c
@@ -769,7 +769,11 @@ static int lvts_golden_temp_init(struct device *dev, u8 *calib,
 	 */
 	gt = (((u32 *)calib)[0] >> lvts_data->gt_calib_bit_offset) & 0xff;

-	if (gt && gt < LVTS_GOLDEN_TEMP_MAX)
+	/* A zero value for gt means that device has invalid efuse data */
+	if (!gt)
+		return -ENODATA;
+
+	if (gt < LVTS_GOLDEN_TEMP_MAX)
 		golden_temp = gt;

 	golden_temp_offset = golden_temp * 500 + lvts_data->temp_offset;

---
base-commit: 632483ea8004edfadd035de36e1ab2c7c4f53158
change-id: 20240603-mtk-thermal-calib-check-ba2ec24a1c32

Best regards,
-- 
Julien Panis <jpanis@...libre.com>