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Patch "hwmon: (pmbus) Use 64bit math for DIRECT format values" has been added to the 4.14-stable tree

PATCH [email protected] 1 participant 1 message Feb 1, 2018

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This is a note to let you know that I've just added the patch titled

hwmon: (pmbus) Use 64bit math for DIRECT format values

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
hwmon-pmbus-use-64bit-math-for-direct-format-values.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From foo@baz Thu Feb 1 13:45:42 CET 2018

From: Robert Lippert <[email protected]>
Date: Mon, 27 Nov 2017 15:51:55 -0800
Subject: hwmon: (pmbus) Use 64bit math for DIRECT format values

From: Robert Lippert <[email protected]>

[ Upstream commit bd467e4eababe4c04272c1e646f066db02734c79 ]

Power values in the 100s of watt range can easily blow past 32bit math limits when processing everything in microwatts.

Use 64bit math instead to avoid these issues on common 32bit ARM BMC platforms.

Fixes 442aba78728e ("hwmon: PMBus device driver")
Signed-off-by Robert Lippert <[email protected]>
Signed-off-by Guenter Roeck <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/hwmon/pmbus/pmbus_core.c |   21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)
drivers/hwmon/pmbus/pmbus_core.c +12 -9
@@ -21,6 +21,7 @@
 
 #include <linux/debugfs.h>
 #include <linux/kernel.h>
+#include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/err.h>

@@ -499,8 +500,8 @@ static long pmbus_reg2data_linear(struct
 static long pmbus_reg2data_direct(struct pmbus_data *data,
 				  struct pmbus_sensor *sensor)
 {
-	long val = (s16) sensor->data;
-	long m, b, R;
+	s64 b, val = (s16)sensor->data;
+	s32 m, R;
 
 	m = data->info->m[sensor->class];
 	b = data->info->b[sensor->class];

@@ -528,11 +529,12 @@ static long pmbus_reg2data_direct(struct
 		R--;
 	}
 	while (R < 0) {
-		val = DIV_ROUND_CLOSEST(val, 10);
+		val = div_s64(val + 5LL, 10L);  /* round closest */
 		R++;
 	}
 
-	return (val - b) / m;
+	val = div_s64(val - b, m);
+	return clamp_val(val, LONG_MIN, LONG_MAX);
 }
 
 /*

@@ -656,7 +658,8 @@ static u16 pmbus_data2reg_linear(struct
 static u16 pmbus_data2reg_direct(struct pmbus_data *data,
 				 struct pmbus_sensor *sensor, long val)
 {
-	long m, b, R;
+	s64 b, val64 = val;
+	s32 m, R;
 
 	m = data->info->m[sensor->class];
 	b = data->info->b[sensor->class];

@@ -673,18 +676,18 @@ static u16 pmbus_data2reg_direct(struct
 		R -= 3;		/* Adjust R and b for data in milli-units */
 		b *= 1000;
 	}
-	val = val * m + b;
+	val64 = val64 * m + b;
 
 	while (R > 0) {
-		val *= 10;
+		val64 *= 10;
 		R--;
 	}
 	while (R < 0) {
-		val = DIV_ROUND_CLOSEST(val, 10);
+		val64 = div_s64(val64 + 5LL, 10L);  /* round closest */
 		R++;
 	}
 
-	return val;
+	return (u16)clamp_val(val64, S16_MIN, S16_MAX);
 }
 
 static u16 pmbus_data2reg_vid(struct pmbus_data *data,

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/hwmon-pmbus-use-64bit-math-for-direct-format-values.patch