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

commit bd467e4eababe4c04272c1e646f066db02734c79 upstream.

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 <rlippert@google.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
[bwh: Backported to 3.2: use integer literals instead of S16_{MIN,MAX}]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index d89b33967a852b8975f09cb5cea88371f1d52e85..d62b08620427de869dc1a31ad0b99684e1cfeece 100644 (file)
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -19,6 +19,7 @@
  */
 
 #include <linux/kernel.h>
+#include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/err.h>
@@ -475,8 +476,8 @@ static long pmbus_reg2data_linear(struct pmbus_data *data,
 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];
@@ -504,11 +505,12 @@ static long pmbus_reg2data_direct(struct pmbus_data *data,
                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);
 }
 
 /*
@@ -620,7 +622,8 @@ static u16 pmbus_data2reg_linear(struct pmbus_data *data,
 static u16 pmbus_data2reg_direct(struct pmbus_data *data,
                                 enum pmbus_sensor_classes class, long val)
 {
-       long m, b, R;
+       s64 b, val64 = val;
+       s32 m, R;
 
        m = data->info->m[class];
        b = data->info->b[class];
@@ -637,18 +640,18 @@ static u16 pmbus_data2reg_direct(struct pmbus_data *data,
                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, -32768, 32767);
 }
 
 static u16 pmbus_data2reg_vid(struct pmbus_data *data,