| Message ID | 20171127213914.141687-1-rlippert@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Mon, Nov 27, 2017 at 01:39:14PM -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@google.com> > --- > drivers/hwmon/pmbus/pmbus_core.c | 23 ++++++++++++++--------- > 1 file changed, 14 insertions(+), 9 deletions(-) > > diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c > index 52a58b8b6e1b..ff701502974a 100644 > --- a/drivers/hwmon/pmbus/pmbus_core.c > +++ b/drivers/hwmon/pmbus/pmbus_core.c > @@ -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 +500,9 @@ 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 b, R; Do b and R have to be s64 ? Seems excessive. > + s32 m; > > m = data->info->m[sensor->class]; > b = data->info->b[sensor->class]; > @@ -528,11 +530,12 @@ 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); > } > > /* > @@ -656,7 +659,9 @@ 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 b, R; Same question as above - do those have to be s64 ? > + s32 m; > + s64 val64 = val; > > m = data->info->m[sensor->class]; > b = data->info->b[sensor->class]; > @@ -673,18 +678,18 @@ 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, S16_MIN, S16_MAX); > } > > static u16 pmbus_data2reg_vid(struct pmbus_data *data, > -- > 2.15.0.417.g466bffb3ac-goog > > -- > To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Nov 27, 2017 at 2:11 PM, Guenter Roeck <linux@roeck-us.net> wrote: > On Mon, Nov 27, 2017 at 01:39:14PM -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@google.com> >> --- >> drivers/hwmon/pmbus/pmbus_core.c | 23 ++++++++++++++--------- >> 1 file changed, 14 insertions(+), 9 deletions(-) >> >> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c >> index 52a58b8b6e1b..ff701502974a 100644 >> --- a/drivers/hwmon/pmbus/pmbus_core.c >> +++ b/drivers/hwmon/pmbus/pmbus_core.c >> @@ -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 +500,9 @@ 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 b, R; > > Do b and R have to be s64 ? Seems excessive. b has a range of -32767 to 32768 and is multiplied in the code below by 1,000,000 for a power sensor so I think needs to be 64bit to avoid overflow. R has limited range so changed in v3 to s32 type. > >> + s32 m; >> >> m = data->info->m[sensor->class]; >> b = data->info->b[sensor->class]; >> @@ -528,11 +530,12 @@ 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 (also fixed up in v3 this C++ style comment that slipped in...) >> R++; >> } >> >> - return (val - b) / m; >> + val = div_s64(val - b, m); >> + return clamp_val(val, LONG_MIN, LONG_MAX); >> } >> >> /* >> @@ -656,7 +659,9 @@ 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 b, R; > > Same question as above - do those have to be s64 ? > >> + s32 m; >> + s64 val64 = val; >> >> m = data->info->m[sensor->class]; >> b = data->info->b[sensor->class]; >> @@ -673,18 +678,18 @@ 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, S16_MIN, S16_MAX); >> } >> >> static u16 pmbus_data2reg_vid(struct pmbus_data *data, >> -- >> 2.15.0.417.g466bffb3ac-goog >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c index 52a58b8b6e1b..ff701502974a 100644 --- a/drivers/hwmon/pmbus/pmbus_core.c +++ b/drivers/hwmon/pmbus/pmbus_core.c @@ -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 +500,9 @@ 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 b, R; + s32 m; m = data->info->m[sensor->class]; b = data->info->b[sensor->class]; @@ -528,11 +530,12 @@ 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); } /* @@ -656,7 +659,9 @@ 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 b, R; + s32 m; + s64 val64 = val; m = data->info->m[sensor->class]; b = data->info->b[sensor->class]; @@ -673,18 +678,18 @@ 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, S16_MIN, S16_MAX); } static u16 pmbus_data2reg_vid(struct pmbus_data *data,
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@google.com> --- drivers/hwmon/pmbus/pmbus_core.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-)