FAILED: patch "[PATCH] hwmon: (lm70) Fix rounding of negative temperatures" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] hwmon: (lm70) Fix rounding of negative temperatures" failed to apply to 5.15-stable tree

[Sasha Levin]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x eddb0aaacce4baa9d8176eb2f4bd9e99e867f8fc
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107060016-failed-5.15-eddb0aaacce4@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From eddb0aaacce4baa9d8176eb2f4bd9e99e867f8fc Mon Sep 17 00:00:00 2001
From: Ridham Khurana <khurana.ridham222@gmail.com>
Date: Thu, 24 Sep 2026 20:53:23 +0000
Subject: [PATCH] hwmon: (lm70) Fix rounding of negative temperatures

temp1_input_show() drops the low bits of the temperature register by
dividing the raw value (raw / 32 on the LM70). These bits are not part
of the temperature: the LM70, LM71, LM74 and TMP122/TMP124 always
return some of them as 1, and the TMP125 fills them with copies of the
temperature LSB. Division rounds toward zero, so a negative temperature
with any of these bits set is reported one LSB too high.

For example, the TMP122 returns 0xffff for -0.0625 degrees C, which the
driver reports as 0. The LM70 returns 0xf39f for -25 degrees C, which
the driver reports as -24750.

Use an arithmetic right shift instead, which drops the low bits and
rounds down.

Fixes: e1a8e913f97e ("[PATCH] lm70: New hardware monitoring driver")
Fixes: a86e94dc946d ("hwmon: (lm70) Add support for LM71 and LM74")
Fixes: cd929672a9ef ("hwmon: (lm70) Add ti,tmp125 support")
Cc: stable@vger.kernel.org
Signed-off-by: Ridham Khurana <khurana.ridham222@gmail.com>
Link: https://patch.msgid.link/20260924205326.1739229-1-khurana.ridham222@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/lm70.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/hwmon/lm70.c b/drivers/hwmon/lm70.c
index 8b525725fef4f..b29bac7a4cc14 100644
--- a/drivers/hwmon/lm70.c
+++ b/drivers/hwmon/lm70.c
@@ -96,21 +96,21 @@ static ssize_t temp1_input_show(struct device *dev,
 	 */
 	switch (p_lm70->chip) {
 	case LM70_CHIP_LM70:
-		val = ((int)raw / 32) * 250;
+		val = ((int)raw >> 5) * 250;
 		break;
 
 	case LM70_CHIP_TMP121:
 	case LM70_CHIP_TMP122:
 	case LM70_CHIP_LM74:
-		val = ((int)raw / 8) * 625 / 10;
+		val = ((int)raw >> 3) * 625 / 10;
 		break;
 
 	case LM70_CHIP_LM71:
-		val = ((int)raw / 4) * 3125 / 100;
+		val = ((int)raw >> 2) * 3125 / 100;
 		break;
 
 	case LM70_CHIP_TMP125:
-		val = (sign_extend32(raw, 14) / 32) * 250;
+		val = (sign_extend32(raw, 14) >> 5) * 250;
 		break;
 	}
 
-- 
2.53.0

[PATCH 5.15.y] hwmon: (lm70) Fix rounding of negative temperatures

[Sasha Levin]

From: Ridham Khurana <khurana.ridham222@gmail.com>

[ Upstream commit eddb0aaacce4baa9d8176eb2f4bd9e99e867f8fc ]

temp1_input_show() drops the low bits of the temperature register by
dividing the raw value (raw / 32 on the LM70). These bits are not part
of the temperature: the LM70, LM71, LM74 and TMP122/TMP124 always
return some of them as 1, and the TMP125 fills them with copies of the
temperature LSB. Division rounds toward zero, so a negative temperature
with any of these bits set is reported one LSB too high.

For example, the TMP122 returns 0xffff for -0.0625 degrees C, which the
driver reports as 0. The LM70 returns 0xf39f for -25 degrees C, which
the driver reports as -24750.

Use an arithmetic right shift instead, which drops the low bits and
rounds down.

Fixes: e1a8e913f97e ("[PATCH] lm70: New hardware monitoring driver")
Fixes: a86e94dc946d ("hwmon: (lm70) Add support for LM71 and LM74")
Fixes: cd929672a9ef ("hwmon: (lm70) Add ti,tmp125 support")
Cc: stable@vger.kernel.org
Signed-off-by: Ridham Khurana <khurana.ridham222@gmail.com>
Link: https://patch.msgid.link/20260924205326.1739229-1-khurana.ridham222@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
[ sashal: Omitted the TMP125 hunk because TMP125 support is absent. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/hwmon/lm70.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/lm70.c b/drivers/hwmon/lm70.c
index d2a60de5b8de9..0a9d7bdd0d3c1 100644
--- a/drivers/hwmon/lm70.c
+++ b/drivers/hwmon/lm70.c
@@ -90,17 +90,17 @@ static ssize_t temp1_input_show(struct device *dev,
 	 */
 	switch (p_lm70->chip) {
 	case LM70_CHIP_LM70:
-		val = ((int)raw / 32) * 250;
+		val = ((int)raw >> 5) * 250;
 		break;
 
 	case LM70_CHIP_TMP121:
 	case LM70_CHIP_TMP122:
 	case LM70_CHIP_LM74:
-		val = ((int)raw / 8) * 625 / 10;
+		val = ((int)raw >> 3) * 625 / 10;
 		break;
 
 	case LM70_CHIP_LM71:
-		val = ((int)raw / 4) * 3125 / 100;
+		val = ((int)raw >> 2) * 3125 / 100;
 		break;
 	}
 
-- 
2.53.0