On Wed, Nov 22, 2017 at 2:28 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > On Wed, Nov 22, 2017 at 02:08:43PM -0800, Robert Lippert wrote: >> 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. >> >> Signed-off-by: Robert Lippert <rlippert@xxxxxxxxxx> >> --- >> drivers/hwmon/pmbus/pmbus_core.c | 21 ++++++++++++--------- >> 1 file changed, 12 insertions(+), 9 deletions(-) >> >> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c >> index 52a58b8b6e1b..f4efea9f282e 100644 >> --- a/drivers/hwmon/pmbus/pmbus_core.c >> +++ b/drivers/hwmon/pmbus/pmbus_core.c >> @@ -499,8 +499,8 @@ 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 val = (s16) sensor->data; >> + s64 m, b, R; >> >> m = data->info->m[sensor->class]; >> b = data->info->b[sensor->class]; >> @@ -528,11 +528,13 @@ static long pmbus_reg2data_direct(struct pmbus_data *data, >> R--; >> } >> while (R < 0) { >> - val = DIV_ROUND_CLOSEST(val, 10); >> + do_div(val, 10); > > Any reason to not use DIV_ROUND_CLOSEST_ULL ? That macro doesn't quite work for signed division. v2 changes this to use the signed 64bit division functions and I emulated the "round closest" by just adding 5 before dividing. > >> R++; >> } >> >> - return (val - b) / m; >> + val = val - b; >> + do_div(val, m); >> + return val; > > Can this overflow ? Added clamp() to the return values in v2 to prevent overflow when returning a narrower type. > >> } >> >> /* >> @@ -656,7 +658,8 @@ static u16 pmbus_data2reg_linear(struct pmbus_data *data, >> static u16 pmbus_data2reg_direct(struct pmbus_data *data, >> struct pmbus_sensor *sensor, long val) >> { >> - long m, b, R; >> + s64 m, b, R; >> + s64 val64 = val; >> >> m = data->info->m[sensor->class]; >> b = data->info->b[sensor->class]; >> @@ -673,18 +676,18 @@ 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); >> + do_div(val64, 10); > > Same here. > >> R++; >> } >> >> - return val; >> + return (u16) val64; > > Can this overflow ? > >> } >> >> static u16 pmbus_data2reg_vid(struct pmbus_data *data, >> -- >> 2.15.0.448.gf294e3d99a-goog >> -- To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html